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The Max Column: January 2005

By: George Robinson

As 2004 comes to an end and we head inexorably towards Christmas and the New Year, it is no bad idea to reflect on the past twelve months and take a look towards the future. There has been good consolidation and growth in the MAX classes, helped by improved production methods and refinements. Early in 2004 the Rotax factory introduced new plastic caged main bearings, a stronger 16 roller big end and a reworked connecting rod. These three changes have resulted in a virtually bulletproof bottom end. The latest engines in Senior form have proved to be strong and fast, although an earlier engine in good condition is still a very competitive alternative. Contrary to popular belief you do not need to invest in a brand new unit to win races. Our test engine from 2000 which had fastest lap in the race at the Le Mans 24 Hour that year, proved to be the strongest of three tested and completed 20 hours of this year’s race before a clutch bearing failure caused us to change it.

Not a bad record for an engine that has only been rebuilt twice in a long and busy career. Around Easter this year we did hear of some reed petal failures. This was not an epidemic by any means, indeed when we tried to reproduce the problem we could not. However I understand that a production change eradicated the weakness and that the reeds are now stronger than ever. New for 2004 was the right to repair the exhaust system by welding, this strictly forbids the modification of the exhaust. If the system is so badly cracked that it might appear to have been completely opened to modify the internal dimensions or volume, my advice would be to start again with a new one. Generally speaking the exhaust is a pretty robust bit of kit and barring an accident should last for several years. It must be properly rubber mounted and most dealers now stock suitable silent blocks which help to protect the exhaust from vibration and do not allow it to become a stressed member of the back of the kart!

Rotax are to introduce a clutch support plate to improve the potential lifetime of the clutch shoe fulcrum pins. The new plate can be fitted to existing clutches without modification. You simply remove the three retaining circlips, remove and discard the flat washers behind them, install the support plate, refit the circlips and the job is done. As reported last month, the Dell’Orto carb has been replaced by an almost identical unit with air bleed and idle speed screws moved to the other side of the body. However, more importantly, Rotax have been testing various options to improve driveability. Their decision is to introduce an alternative needle from January 1st This is designated K98 and will be eligible as well as the existing K27. At some point in the new year, Rotax will be introducing an alternative battery. This will be of exactly the same dimensions as the existing unit. The new battery has a slightly changed production method and is designed to be more reliable.

The venues and dates for the Rotax Euro Challenge have just been announced. They are the 25-27th March at Salbris, France, 27-29th May at P.F. International, 29-31st July at the Al Speedworld, Austria, with the final on the 16-18th September at Genk, Belgium. All these are easily accessible from the UK and are some great circuits, let’s hope we get some real quality interest from some of our top teams and drivers. We have the strongest market in Europe for the MAX so let’s forget the soft bellied nanny state we are expected to live in, get over there and give the foreign Johnnies a good seeing to! On a completely different subject, a lot of older racewear is becoming obsolete at the end of the year. Unfortunately your favourite suit with its three digit CIK number will no longer be eligible for racing, the good news is that I am fairly sure that the average race suit is now cheaper than it was say ten years ago. There is certainly more choice than ever before in masses of styles and colours to suit every taste, although I think it is always worth going for a size that you may think is too big. Try not to be a fashion victim for a second and just consider that you must have good freedom of movement when you are seated in the kart. If you are trying to impress girls by your tailored fitting suit, you might find yourself having to do three point turns to negotiate the tighter hairpins and the girls just might brush past you on their way to congratulate the bloke in the baggy suit who won the race. Have a good look through the pages of this magazine and you will find a number of companies marketing proprietary brands of race wear, those offering mail order will certainly offer an exchange or money back service should the goods not meet with your expectations.

If 80 First in the World for 44 years possible visit one of the larger karting retailers where you can try on a variety of different clothing. There are also some helmets which will be up for renewal next year. This is such a specialised area that I am certainly not qualified to advise. The best idea has to be to go to an outlet where they have a very wide choice for you to try on. I believe that helmets are a bit like shoes, everyone’s feet are different and so are their heads. A helmet should be a snug fit, if anything tighter rather than looser when new A balaclava can make quite a difference to the fit of a helmet but these are an acquired taste, some people love them, others hate them. Just be sure to try the helmet on as you would intend to use it. Furthermore, it is important to check the manufacturing date of the helmet and its eligibility for karting. Also ensure that there is a ready supply of new visors and fitting kits. I bought a helmet three years ago and ordered a couple of spare visors at the same time.

“No problem” they said, except that the iridium (fashion victim) visor never turned up and never went into production for that helmet, so beware. I believe that the dates for the MAX Challenge qualifiers will be finalised by the time you read this, unfortunately there are a couple of confirmations still to come through. It would be very good to see a strong turnout next year and I have heard that the new MOJO tyre is very similar to the outgoing Bridgestone YGK which cannot be at all bad. There will be classes for Juniors and Seniors and the Rotax regulations also allow for drivers to enter Seniors from the age of 15 for the 2005 International Challenge. This issue of the magazine will be out between the Telford and Sandown shows so hopefully some of you will already have been to Telford and one or two may have attended the MAX seminars there.

The Karting magazine forums to give them their correct title are always well attended which has to make them worthwhile. It does give people the opportunity to hear about the latest news and also benefit from the questions and answers element of the meetings which always runs into extra time. I find these forums very interesting, they are never the same because it is the audience who ask the questions. At Sandown Park the seminars are entitled Master Classes and were very well attended last year. Both shows are now well established and are a highlight of the winter calendar. As this is the last issue before Christmas I hope you all have a good one and please make sure that your MAX has some antifreeze in it before you start tearing the legs off the turkey.

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The Max Column: december 2004

By: George Robinson

The Super 1 and Stars of Tomorrow series are now over and those who are not looking at winter racing can relax a little, with the prospect of venturing out in early December to the kart shows. The first weekend sees a slightly later than usual date for the well supported Telford exhibition with the second Sandown show just a week later. I think it will take a particularly dedicated individual to visit both when we are mostly under considerable domestic pressure to go Christmas shopping. Yuk! Both of the shows are now well established on the karting calendar and I have been asked to host the Rotax forums at Telford and the Masterclasses at Sandown. Please come and ask as many awkward questions as you like, I blush easily but don’t worry, it means nothing! I hear that both Sandown and Telford are virtually fully subscribed in terms of exhibitors so there should be plenty of interest for all sections of the karting world. There is sure to be a very solid Rotax element at the shows with all retailers now supplying more CIK type chassis for the MAX classes than all the rest put together.

Market forces dictate where people spend their money. The Rotax MAX remains the karting phenomenon of the past decade and probably the largest single change in the direction in karting since the sport began in the late 1950s. There is a wind of change at the CIK and I believe that we shall see a less aggressive approach to the introduction of 4-stroke engines and classes. There is new exciting development of the 2-stroke and I believe that a super efficient lean burn eco-friendly engine is a very real probability in the not too distant future. The sooner the racing 4-stroke is recognised for what it is and the true costs evaluated the better it will be for the sport of karting to move ahead. All the talk of the imminent introduction of 4-strokes has done nothing more than destabilise the industry as a whole. Before the Rotax MAX came into being, 100cc racing was already in decline if not in crisis.

The MAX has offered a perfect template from which to build the future structure of kart racing both here in the UK and on the international scene. There are now examples of clutched self-start engines available from every major kart engine producer. Some are fast, some not so fast, some expensive and some not so reliable. I believe it is fair to say that without Rotax taking the bold step into a completely different type of power unit we would still be waiting for the other manufacturers who are now producing 125 TAG engines to come to the sport’s rescue with a wide range of products. The winter is coming on strong now and it cannot be a bad idea to check that your MAX engine is filled with the appropriate coolant and anti-freeze. Many a kart is laid up at this time of year and forgotten until the temperature improves in the new year, by then plain water in the cooling system will have frozen and done considerable if not irreparable damage to the engine.

The carburettor should also be cleaned, emptied of fuel and ideally sprayed internally with a WD40 type product to save the aluminium from pickling up in the cold and damp conditions, in fact the whole engine could do with a good coating of WD to stop the same thing happening to the outside. Likewise the kart will also suffer unless all the unprotected areas are treated. Following a lot of talk and certainly some advantage being gained by the use of some types of spark plug, JAG have printed a list of approved plugs that are the only ones that may be used from January 1st 2005. They are as follows;
Denso: 1W24, 1W27, 1W29, 1W31. Champion: QN84, QN86. NGK: BR8EG, BR9EG, BR10EG, B8EG, B9EG, BlOEG, B8EGV, B9EGV, BlOEGV, BR8EIX, BR9EIX, BR1OEM.
All the above have been tested and provide a good consistent level of performance. There will be slight variation in jetting and there are bound to be claims that one or other of these plugs gives an advantage. I suspect that this may well be due to the carburation being better suited on a particular day to one plug rather than another.

The Denso and NGK references with an ‘IV are resistor plugs and the Denso and NGK `ElX’ are Iridium which are reputedly a higher quality giving superior burn characteristics. They are certainly more expensive than the other plugs on the list. There is a good spread of price and quality to suit all pockets and a wide enough range for there always to be an alternative should there be any shortage of supply. From next year the position of the fuel pump will be standardised to the position 28 First in the World for 44 years under the carburettor fitted to the bracket that also secures the air box.

The reason for this change is because the fuel pump is much more efficient at blowing than drawing the fuel, in other words it will provide a more consistent and adequate supply of fuel if the pump is lower on the kart in relation to the petrol in the tank. There is no need to go to the lengths of a bottom feed from the tank that some favour, the pump is more than capable of providing enough fuel with the standard top feed. Always make sure that the pick up in the tank is in good condition, if the pipe has gone hard then it cannot follow the fuel around the tank and you will suffer from surge when the level drops below half full.

The latest delivery engines are coming through supplied with a new version of the Dell’Orto VHSB 34 carburettor. There are no specification changes that can possibly affect performance. The idle and air bleed screws have been moved to the other side of the carburettor body to facilitate adjustment, the carburettor remains unchanged in every other aspect. To help compensate for the increased weight of modern CIK bodywork, weight limits are to increase next year by two kilograms in all classes except Minimax, which will remain unchanged at 135kg. The new weight for Juniors is to be 145kg, Seniors 162kg and Heavy 177kg. The last round of the MAX Euro Challenge saw Tristram Oman score a well deserved 3rd place overall earning him another crack at the World Finals, joining David Bellchambers as the UK representatives in the Senior class. Adam Christodoulou makes the trip for the Juniors while James Tumulty is the representative for Ireland in Seniors. The event is scheduled for the third weekend of January in Lanzarote. The Euro Challenge has been very successful and well supported, the best of the rest of the Brits being Ben Cooper who finished a very creditable 3rd overall in Juniors.

The dates for next year’s Challenge are already set with the venues to be confirmed soon. The British teams running in the French Endurance championships had a fine end to the season with 1st, 2nd, and 3rd in the MAX class at the last round of the championships in Pageas near Limoges. This is the best result that the Screenvyn team have scored so far and will encourage them to greater things in the coming season no doubt. The Pageas circuit is well suited to the MAX, although the Formula A teams were ultimately faster their ability to overtake was much reduced. Timed qualifying saw Martin Pierce top the MAX times on a Select chassis only three tenths off the pole setting 100cc time. Roll on the future of 125cc 2-stroke karting.

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The Max Column: November 2004

By: George Robinson

I can only apologise for the brevity of the MAX Column last month. Due to my probable ineptitude with anything connected with computers, two pages of text disappeared from view between my home and the magazine office! The dates for the 2005 Euro Challenge have just been published although the venues are not definite yet. Round 1 will be on the 22nd – 27th March with round 2 on the 24th – 29th May. Round 3 takes place on the 26th – 31st July with the final event on the 18th – 23rd October. The World Finals will be held in Lanzarote from the 17th to 22nd of January 2005. I have never been there but understand that the weather in January is usually like a good summer’s day in England. Lanzarote is of course a very popular holiday destination, with lots of sun, sea, sand and other nocturnal attractions! A slightly unnerving technical issue has come to light recently. Some new carburettors have been delivered with a non-standard needle jet atomiser FN266. Although the atomiser is identically stamped with its part number, these rogue tubes have only three cross drillings instead of the standard four.

JAG have circularised a clarification to the effect that it remains the competitors’ responsibility to ensure that his or her equipment conforms with the regulations.
After an awful lot of talk about spark plugs, complete with the usual proportion of nonsense, it is now certain that JAG will introduce a list of approved plugs that can be used. This will help the inexperienced competitor to install a spark plug that will perform correctly without compromising reliability. Since this latest craze to find the very real performance advantages using some of these alternative plugs, there have been a number of engine failures that can only be attributed to the plug and, either an incorrect heat range or, worse still, a heat range that has changed in use due to the gradual failure of the central electrode. Furthermore, there have been reports of `the right plugs’ changing hands for up to £200 when there were only a handful around and as little as £50 when they became more readily available.

At least one company are in the process of getting their fingers burnt having been offered exclusive import rights as it soon became clear that anybody could get the product and at prices down to less than £15. This is still a lot of money for something that can do hundreds of pounds worth of damage to your engine. An approved shortlist of spark plugs is certainly the answer and the sooner the better in my opinion. I understand that TKM are taking the same very sensible action to cover all their classes.

More rumour has begun following some tyre testing that we have been doing recently. There are to be no changes to the tyres used in the foreseeable future, the Vega tyres in Junior, Senior and wet form have been very successful. There will always be talk of variation in performance and even if there is no difference there will still be talk. The fact remains that tyres will vary and anyone who believes otherwise needs to wise up! The Vega range, thanks to the commitment made by JAG and Deavinsons, the importers, are almost always readily available and, because they are produced in Europe, there is a shorter lead time than those brands manufactured in the far east. This helps to keep the time between production and use down to a minimum. Generally speaking the fresher a tyre is the better it is but this is due in part to the fact that the tyre has had less time to be abused since production.

Tyres are adversely affected by ultra violet light, so leaving them out in the sun or even daylight is not a good move. Ideally buy your tyres where you expect the dealer to have a fairly quick turnover and if so he probably stores them in their original cardboard boxes. The plastic wrapping on the tyres will discolour if left in daylight, when new it is crystal clear and will soon turn brown with age or light. This does not mean that the tyres are scrap, but it is an indicator as to how long they may have been stored and how carefully. There has been talk of tyre treatment, I am told that this can now be detected in all its forms which has to be a good thing.

I heard 64 First in the World for 44 years an argument just the other day to allow tyre treatment, I have to totally disagree, you might as well open all the classes up to open tyres and see the immediate destruction of racing as we know it. There is no quicker way of bolting on performance than fitting softer tyres, all the classes in this country, with the possible exception of Formula A, use a relatively hard compound tyre giving a suitable level of grip for the power of each class. I have always been a great believer in the window of power to grip level being correct, I think this has been achieved in the MAX classes here and there is no reason to consider changing it. The tyre testing we have been doing recently has been conducted on behalf of Rotax who have been looking at a tyre that they can use to replace the Bridgestone World Finals tyre. Rotax have been working with Heidenau who have little experience in kart racing tyre production. In view of this their first product was not at all bad, but I believe it is some way from going into production and there is more work to be done first.

As I said before, it will certainly not affect the British market at all. Probably the hardest subject of all to cover here is the carburettor, I promised to do it last month and am now regretting it.

A good carburettor functioning properly is a performance advantage that should be available to all but in reality is only achieved by very few. The Dell’ Orto VHSB 34 is a very reliable product that can be tuned to suit all the MAX classes reasonably well, at least it’s the same for everybody, or is it? I believe it is very rare to find that you have a carburettor that will never work, however the carburettor is a mass produced item and as such must be susceptible to variation. Within the regulations we are allowed to run two types of venturi, the older type 12.5 and the more recent 8.5.

There has been much debate about which is the best and in reality there is not a great deal of difference between two good ones. The general consensus of opinion is that the 12.5 is a little easier to drive and requires less of a balanced throttle than the 8.5. In either case the carburettor must be working properly to perform. It is worth stripping a new carburettor right down before using it since there may well be some production debris lurking in the jet bores. The only way of cleaning this efficiently is to strip the body bare, clean with carburettor spray and then blow it out with an airline. The floats are often set a little low, in other words, not allowing enough fuel into the float chamber. The lever arms should be parallel to the carb body when left to sit with the body upside down. This is something that can be experimented with.

Too low a float level will produce fuel starvation out of corners, over bumps and at the end of the straight. Too high a float level will lead to indecisive changes to jetting and an inconsistent over richness that can be difficult to diagnose, More carburettor details next month.

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The Max Column: october 2013

By: George Robinson

I have been under pressure to produce this latest column on time because, unfortunately, the magazine staff knew that I was about to disappear off to Le Mans for the annual 24-hour race for 2-strokes, the international event which has world championship status among the endurance racing fraternity. Without blowing my own trumpet too hard (if I don’t who else will?), I have over the years had as many podium finishes as anyone, be it on Zips, TKMs, CRGs and twice with Birel, all of them using Parilla power. So, you are thinking, why has the old fool started to ramble again when he’s supposed to be talking about the MAX? Well, if you can bear with me, it’s because the MAX can seriously compete with the top Formula A engines at this level. The weight limits have been adjusted to make it a more even playing field. The 100cc boys are now expected to tip the scales at a gentlemanly 155kg, while the MAX remains at its competitive fighting weight of 160kg.

George monitors a pit stop at Le Mans at the 6-hour race back in June Le Mans is still, as ever, a superb if slightly dated circuit by French standards and requires a good total package of chassis, engine and driver. The overriding features of the track is that it requires a lot of mid-range power and good accuracy, if not ultimate speed, from the driver. The MAX delivers lots of mid-range and, providing the chassis is up to it, then they can certainly match the 100s on this circuit. The 100cc teams will schedule engine changes at 6 or 8 hours, while the MAX is more than capable of running straight through the 24 hours and then winning a club race the following week after a dust off and a new sprocket. The alternative `Touch and Go’ engines have all tried to take on this race and so far have all benefited from 16-year-old Ruth Senior from Wymondham in Norfolk was the worthy winner of the `B.E.S. T-Cars Scholarship in association with Karting magazine’ which we helped organise in 2002. Ruth is now in her second season of T-Car racing and will keep us regularly updated on her progress.
CHAMPIONSHIP (after 14 rounds) 1 Will Bratt 274 points, 2 Fredrik Nordstrom 238, 3 Daniel Thackeray 217, 4 Ruth Senior 194, 5 James Williams 174, 6 Toby Newton 138.
an early bath. The MAX is the only real alternative to the 100s capable of knocking them off their perch. The latest components in the MAX are certainly the best yet. The new con-rod and big end are virtually trouble free, as are the new main bearings. The new Senior engines are every bit as strong as any we have seen over the past five years, although I am glad to say that our faithful test engine, which produced the fastest lap in the race at Le Mans in 2000, will be out there again this year, having proved itself as being perfectly quick enough after a rebuild to install the new components. I’ll let you know in next month’s issue how we got on.Postcard from Ruth Qualifying at Mondello Park turned into a race against flagged because none of my times were registering. It time as a couple of minutes into the session I was black  turned out that we id’t have the correct Irish transponder and after one was found  and fitted there were only two minutes remaining to qualify. of this I was Race one lasted just3.3 seconds.

I made a good start and moved into 3rd but was hit from behind going into the first corner, spun and was then hit head on. It didn’t do quite pleased to line up 4th. much for the car, it was in such a state that it had to be carried back to the paddock The team did a brilliant job sticking everything back together in time for race two. Starting from the back, I drove cautiously as the track was very lippery. I by crane. I had another poor weekend at Anglesey, finishing 4th in both contact-filled races. ended up 4th, not perfect but atleast finished. Starting 4th in race one, I made a quick start and was immediately up into 3rd. But, like at Mondello, I was ‘knocked from behind, this time by Fredy, and spun into last place. Fortunately, I was able to get going again and overtook a couple of cars at the In race two I made it round the first corner without incident in 3rd. Then on lap hairpin and another at Douglas to regain4t.

two I was gifted the lead when Dan and Will touched. Four and a half laps later though it all came unstuck when Freddy barged his way past, pushing me onto the grass and knocking off my splitters. I dropped to 3rd and was passed by Will a few The next races are at Snetterton but before that there’s a T-Car open day at laps later, again being tapped onto the grass. Bedford Autodrome, with testing time for the drivers and passenger rides for any potential competitors. Hopefully the chance to test will prove valuable and Ill be able to repeat my result from the first round at my home track, Snetterton, by winning!IBRSCC T-CAR CHAMPS Rounds 11 & 12 Mondello park Rounds 13 & 14 Anglesey Ruth First in the World for 44 years

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The Max Column: september 2004

By: George Robinson

Spark plugs! Who’d have thought a serious performance advantage could be gained simply by changing the spark plug. The fact is that to run some of these plugs can be extremely risky. We have just had the hottest weekend of the year so far and I know of some engine failures that can only be attributed to the spark plug. I won’t name and shame any particular brand but they have only just become available and I am aware of several different types. Unfortunately, there is evidence of a performance advantage, however, some of these plugs are prone to oiling up. There is also evidence the plug can cause detonation that will eventually hole the piston or cause a seizure. This may not be entirely the fault of the plug, it could be the use of a plug with the wrong heat range. Either way, you are left with an engine in need of expensive professional help.

Until the suppliers can give sound advice on the correct plugs to use in each type of engine, I can only advise you to stick to the original or a direct equivalent from a proprietary manufacturer. The Denso Iridium plug is reliable as are those from NGK and Champion providing that you always buy the correct heat range. There have been some battery failures recently. The batteries at fault are not those supplied by Rotax. It is perfectly acceptable to fit an equivalent battery within the regulations, unfortunately there has been a batch that seems to be damaged almost immediately by vibration. If you have suffered from this you must return the battery to your supplier who should give you a replacement as long as the faulty unit is not externally damaged.

These batteries are marked with a date code and batch numbers, so please don’t question your supplier’s intelligence by trying to claim a new battery against a wrecked two year old example. There is a really excellent product I have just started using called the Intelligent Battery Tester that accurately measures battery voltage and amp hours while taking temperature into account. I have found huge differences in batteries I had previously believed to be in perfectly good condition. It is not only essential to have a battery in top condition for starting but also for good consistent performance. I know some people use a slave battery to start their engines but with a battery in good condition showing
plenty of amp hours this is completely unnecessary. I suspect the tester would cost a bit more than a slave battery kit but you are really solving the problem at source. As promised, I want to touch on the maintenance of the plastic gear cluster behind the cover on the left hand side of the engine. The plastic gears are often forgotten on the old premise of being out of sight, out of mind. In many cases the memory is only jogged by almost undriveable vibration! A good starting point to try to avoid this is to check the condition of the oil at the end of each day out. If it is discoloured at all, or worse still contains any white specks then immediate investigation is required. Even if the oil is not dirty I always take the side cover off, check the gears, give the whole casing a good clean and replenish with fresh oil. That way you are unlikely to ever experience any problems.

If there is any sign of wear on the gears then I believe in replacing them all. Wear tends to build up throughout the gear cluster, so for the sake of an extra £10 I usually put in a new idler and pump pinion as well. The late type black plastic crank drive gear is also cheap to replace and the early steel one never gives any trouble. At the very least, the large balance gears must be replaced as a pair. To remove the balance gears it certainly helps to warm them slightly, to around 50° C, having first removed the two retaining clips to expose the rubber 0 ring on the crankshaft and the oil seal. If the gears have broken up badly or run for any length of time without oil then shards of hard plastic can damage the oil seal and even work their way through the balance shaft bearing. The latter is potentially the most serious problem, if you can see any debris in the bearing then the engine has to be stripped to properly clean or replace the bearings. Reassembly of the balance gears is relatively straightforward, providing you have everything to hand.

Having checked the 0 ring and oil seal, I usually lightly oil the splined shafts before warming the two balance gears. There are hot air guns available but a high powered hair drier will probably do the trick. Alternatively, submerging the gears in a recently boiled kettle of water is fine, just remember not to use the same water to make the tea! Although the two large gears are identical they are not fitted the same way round on the two shafts. On the crankshaft the protruding hub boss should be facing outwards, and on the balance shaft the flat side is on the outside allowing the gears to align correctly. The balance gears must be ‘timed’ correctly. With the engine sitting flat on the bench the mark on the balance shaft will be vertical, with this gear fitted it is then simple to align the mark on the crankshaft with the cast-in pointer on the crankcase and slide the second gear into place. Having pushed the gears home but without too much force, fit the main drive gear onto the crank and install
the retaining circlips.

There is a right and a wrong way round for circlips. If you look carefully you will see on one side they have a rounded finish while on the other the finish is much sharper. The sharp side should always take the load or be on the outside, maximising the efficiency of the clip and minimising the chance of it coming off in use. The water pump pinion is next. Be sure the washer is in place on the pump shaft first followed by the drive pin and then the pinion itself. Lastly, just push the idler onto its shaft, refit the gear cover with a new gasket if necessary and replenish with oil. Rotax recommend a 15W40 grade of good quality motor oil. When refitting the retaining bolts, always remember the two bolts with copper washers must be fitted in the drain hole at the bottom and the first hole up to the left that doubles as a level plug. The clutch is another area frequently ignored until it breaks, and, if it breaks, it will usually need to be replaced. To remove the clutch a couple of special tools will be required.

It is possible to use the piston stop, however I prefer the geared type of engine stop that meshes into the starter ring gear and positively stops the engine at the point where you are about to apply the load. A 30mm deep socket will be required to undo the clutch retaining nut. This nut is tightened to a torque of 100Nm and it can be very hard to break the Loctite seal. The appropriate grade here is the green bearing fit type No. 648. This is substantially stronger than Nutlock and is the reason I prefer to use the geared engine stop as described above. With the clutch nut removed you will need to install the correct puller in order to safely remove the clutch without damage. This completed you can now examine the condition of all the components including the shoes and starter reduction gear. The clutch shoes should not move laterally on the fulcrum pins. If they do, this proves wear in the aluminium bores and the only solution is to replace all three shoes. There is a repair kit including all the assembly components which when fitted with a new set of shoes makes the clutch as good as new providing the pins are in good condition.

A small coating of copper slip grease on the pins before assembly is worthwhile and be sure to point the ears of the circlips outwards, that way they cannot be affected by centrifugal force. The starter reduction gear or Bendix’ is very reliable despite its fairly hostile environment. At the very least it should be thoroughly cleaned. The housing can also do with a good wash out giving you the opportunity to check the bearing at the back, a little grease here will not go amiss. I lubricate the Bendix with light oil then refit the plastic outer cover, grease the bearing area and fit the two Allen screws with Nutlock. That’s all for this month, in the next issue I expect to have more news on the spark plug story and hopefully an in depth look at the carburettor.

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The Max Column: august 2004

By: George Robinson

perhaps it is hardly surprising that after five years of writing this monthly column it is sometimes hard to find new and interesting content to happily fill a page, when the subject is as narrow as the development and evolution of just one type of engine, the Rotax MAX. The solution to this problem is either to simply stop or to change the way in which the column is compiled. I have had a number of people who urge me not to stop and also, for the first time, some criticism which, being constructive, leads me to look at new ways of keeping the interest level high.

There are so few enquiries which ask for advice on the MAX now that could add weight to the column so alternatives have to be found. The majority of the trade are well versed in the servicing and maintenance of MAX engines, so it has to be to the privateer or first time buyer that the technical aspect of the column is directed. Principally, this has to be focussed on the areas of maintenance outside the sealed part of the engine unit, although it is now true to say that a lot of engines are being used for leisure and non-MSA racing in unsealed form. I propose therefore to concentrate on the external components this month and look at a detailed engine build in the near future. The senior engine allows access to the cylinder head and reed block here in the UK where engines are sealed by JAG. This is not the case abroad where all engines tend to be sealed as per our junior and mini engines, which precludes access to the whole unit. The advantage of being able to remove the cylinder head is that anyone can check the condition of the top of the engine and decarbonise as required.

The engine must of course be rebuilt to the original specification. If there is any doubt about this, the engine must be checked by an approved service agent to be sure that it is still within the fiche measurements. Any machining or polishing is expressly forbidden within the regulations. There should be very minimal carbon build ups in the head or on top of the piston if the correct 100% synthetic oil has been used. There
is usually some oil residue in the power valve bellows. This should be cleaned regularly to avoid softening of the rubber, which will shorten the life of the bellows. A new type retaining spring should be installed at the same time. This will greatly reduce the risk of the bellows blowing off the plastic piston. While in this area, check the condition of the exhaust retaining springs as these can become stretched or weakened by wear in the hook where they pass through the exhaust flange. The exhaust springs are so cheap that it has to be worth replacing them early rather than risk failure.

The power or exhaust valve relies on a good seal between the flange and pipe to operate efficiently. Rotax do recommend a specific high temperature silastic to ensure a gas tight seal here. I know many people do not bother to use any jointing compound here or use a standard temperature silicone, which cannot withstand the very high exhaust gas temperatures. Before fitting the exhaust be sure that the pipe is fitting snugly on the flange and that the bottom of the pipe is not fouling on the crankcase casting. The exhaust itself is often ignored. It is worth checking the main body of the pipe for cracks, since everything has a finite life and how well treated the exhaust system has been will determine its life expectancy. Cracks sometimes occur near the mounting bracket This is usually due to the mounting being too rigid.

There are plenty of suitable rubber silent blocks on the market which are inexpensive and will preserve the life of your exhaust The exhaust wadding should be replaced at least every 10 hours and it is well worth replacing the baffle tube at the same time. I prefer to replace the rivets with bolts, 4mm button heads with a nyloc nut do the job perfectly and look almost exactly like the original rivets. That about wraps up the area of the exhaust Just remember that you are only allowed to repair by welding, you may not modify the exhaust in any way and you may only repaint in black. That is the letter of the law.

The reed assembly is another part of the engine that can be service checked by anyone so inclined on the senior engine. Generally very reliable, the reeds are fundamental to good performance and can lose efficiency without the fault being immediately obvious to the naked eye. First of all, check the rubber manifold where it joins the carburettor. This is not a problem area at all, but can be damaged and must have no potential air leaks. The reed block itself is a little more complicated to check. First of all, visually check the reed petals for damage. This usually starts with feathering of the laminate at the outside corners. When this starts to occur, the reeds have already lost a good deal of performance and will deteriorate
68 First in the World for 44 years quickly until total failure, which causes a complete loss of power and difficulty in even starting the engine. The reed petals should sit perfectly flat on the reed block. With use they can become bowed with a corresponding loss of performance. This is sometimes difficult to see. I find the best way is to hold the block up to the light and look along the length of the block to see if there is any light between block and reed. Providing that there are no foreign bodies embedded in the rubber section of the reed block, then the simple solution is a new pair of reed petals. Offer the petals up to the block and be sure to mount them so that the petal lies flat and seals all the way round. So far the above service checks can be carried out without the need for any special tools and the same is true of the starter motor.

There is a starter repair kit available which consists of a pair of carbon brushes and the armature shaft bearing. The most common fault in the starter is when the braided wire from the live side carbon brush frays to the point where it parts. This is caused by vibration and can be easily checked. Firstly, remove the 3 cross head screws which hold the steel body, having taken the motor off the engine. Hold the starter shaft gear very firmly and pull the steel cover off. If you do not hold the gear, then the strength of the magnets will pull the armature out of its housing, thereby releasing the carbons and their springs. The springs will disappear across the room, never to be seen again. Having done this, you should be left with the alloy base casting and armature still in situ. It is then easy to check the condition of the carbons and their braided wires.

I have never seen a carbon brush wear out on one of these motors. The motor does not run for long enough to cause wear, it is only vibration damage we are looking for. Using a small screwdriver or scriber it is possible to move the braided wire from side to side to confirm whether any fraying has started to occur. If so, there is no alternative but to replace the brushes, I always fit the new springs and bearing supplied in the kit as well. Finally, check that there are no cracks around the flange area of the steel body. This can happen and it is acceptable to repair it by welding. I prefer to braze them, there is less heat required and you can get a really good fillet of bronze in there to be sure that the problem does not recur. Since Rotax introduced the starter support ring the incidence of these failures has dramatically reduced, in fact it is now only the older units which were not supplied with the support ring fitted that seem to give any trouble. Next month I will go into the plastic gear cluster, its maintenance and replacement and the clutch assembly, starter gear and bendy.

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The Max Column: July 2004

By: George Robinson

The 2004 season is now well established. All the club and national championships have completed several rounds. Many have been affected by changeable weather conditions and as a result the onus has been placed heavily on teams’ abilities to adapt set-up quickly to maximise performance in difficult circuit situations. It seems that those less well prepared are more inclined to shout “cheat” as soon as anyone else seems to have an advantage. It may however be that there are perfectly legitimate claims regarding the eligibility of some competitors’ equipment and there seems to be a ‘no smoke without fire’ situation when looking at the fuel and tyre treatment issue. I believe that these very real concerns need to be dealt with severely.

If anyone is proven to have used these performance-enhancing products, which are expressly forbidden, why should the culprit be allowed to continue to race? A ban for a long period would surely discourage the culprits. Racing at any level is far too expensive for the honest competitor to be bothered to continue if he knows that he is likely to be beaten by a cheat. In the first instance it might be expensive to bring the perpetrator to book but an example must be set.

There is some fantastic racing going on in all classes in this country, not just in MAX, but also accusations of rule bending going on in every class. As modern technology becomes more readily available to us all, there are greater opportunities to take advantage of the grey areas in the regulations. JAG have a very good and balanced view on the way forward with a set of workable regulations for the MAX classes. This is due in no small part to the fact that John Gravett of JAG has at least 30 years experience in karting, firstly as a successful competitor and more recently as one of the world’s top engine builders for the 100cc market. The fact that all Rotax MAX engines imported into this country pass through JAG and that John personally checks and seals every single one of them does give the MAX classes a huge
advantage. The customer knows that the engines are all within a very tight technical specification and that each engine has a fiche kept on file at JAG. Any engine considered to have been modified illegally can be quickly compared against this original fiche. There are of course other elements outside of the sealed engine unit that could be altered without a service agent’s knowledge. Competitors need to be quite clear that they are responsible for anything that may have been done to improve the performance of their kart or engine and then either accept the consequences if caught or refuse to race until the kart conforms with the regulations. Since the introduction of the MAX there have been a number of alternative 125cc clutched self-starter engines introduced by other manufacturers. This was inevitable in view of the extraordinary success of the Rotax product. Although there are pockets of support for these other products, none have come close to matching the MAX.

The MAX is still capable of delivering speed very close to that of a good Formula A engine if the track conditions allow it, as shown recently when Martin Pierce qualified on the front of the grid at the Euro Endurance round in Brignoles. Next to him was the front running French driver Pierre Combot on a Formula A factory tuned Vortex. Behind him was Alban Martinet, former vice European Champion powered by a Formula A Parilla from Piazza. Not bad company for a humble out of the box sealed MAX. Incidentally, all the other TAG’ engines failed during the course of the six hour event and did not feature in the results. Endurance racing here in the UK has never been stronger for the MAX competitor and there is a wide selection of options available.

Promax is alive and well and living in Kent, and a full series of events is under way run by Bayford Meadows’ circuit management team under Ian Ward. The various Trackside Racing series cater for all Senior MAX teams with a choice of one and a half or three hour races at a variety of venues including Clay Pigeon, Lydd, Enough Park, Buckmore Park and of course Bayford Meadows. I have been lucky enough to be asked to race in some of these races by Martin Collard from Dartford Karting and have really enjoyed myself. There is a good grid and the racing is clean without the cut and thrust of sprinting. Organisers Peter Wraight and his partner Sue do a great job and always have the same staff to help run the meetings. There is a really friendly atmosphere and a former competitor, Neil Ashcroft, is producing a DVD on each round. While there are good grids at most of the races there is usually space for a couple more entries.

It really is well worth a try and a very inexpensive form of racing on a pounds per lap basis. The teams are usually made up of two drivers but three or four is fine. John Oxborrow, fabricator of the Oxkart, races alone and is frequently in the money at the end. Contact Trackside Karting for more details on 01795 473300. One new component coming through from Rotax any time now is a replacement exhaust valve bellows retaining spring. This is the spring around the top of the bellows that holds the bellows in place, not the compression spring which holds the valve closed. The new spring is much stronger than the old one and will help to keep the bellows from blowing off, more common since the replacement exhaust valve piston was introduced. Adjustment of the exhaust valve by turning the red nut does not have the big effect claimed by some dealers, screwing the nut in increases the pressure on the spring which in turn holds the valve in its closed position for longer. If you unscrew the valve nut you will decrease the spring pressure and therefore the valve will open sooner. The best position to start from is with 5mm of thread showing from the top of the black cover to the base of the thread under the turn wheel on the red screw.

This can produce some advantage but should not be overestimated. The total value of adjusting the exhaust valve is probably less than two teeth on the gearing. Despite continued rumours that Rotax are to introduce their new Mojo tyres, there are no plans to do so in the foreseeable future. The tyre is in the very early stages of its development. The existing Vega tyres serve the British market very well and there will be no change to this situation. The only slight disappointment that goes with our adoption of the Vega is that when we are forced to run on Bridgestones to qualify for the World Finals, we do suffer from lack of support in terms of entries.

This is certainly because competitors are faced with having to buy both wet and dry tyres, probably two sets of each, and then only have one or two chances of winning the dream ticket. Unfortunately Rotax’s decision to run next year’s World Finals Senior race on the RM1 has further damaged the dealers’ interest in supporting the world qualifiers. In spite of these setbacks there was a good first round at Shenington with the second due now at P.F. International. The location of the World Final is confirmed for Lanzarote in mid January 2005. Because the destination is not too far away but still potentially warm I understand that there are quite a few British supporters who will be making the trip.