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The Max Column: june 2004

By: George Robinson

The Rotax MAX was introduced in 1997. Direct drive karting was predominately 100cc in three basic types, reed, rotary and piston port induction. These classic engines formed the backbone of club, national and international racing. Leisure karting grew up around the 4-stroke Honda GX used almost exclusively in indoor karting. In the quest for more speed these leisure karts soon had twin engines and tuning aids forming the next step up from the arrive and drive corporate entertainment market.

This potentially huge sector of the new karting public were not the same as the professional and enthusiastic amateur drivers who raced 100cc. Either by very clever market research or partly by mistake Rotax hit on the product to unite these diverse karters. The reason the MAX has been so successful is due to its user friendliness and aggressive pricing. In simple terms, an engine that is delivered complete with all accessories, a clutch and self-starter for about the same price as a contemporary 100cc unit has to be a winner. I believe that even without the arrival of the MAX, 100cc karting was in trouble anyway and badly needed a new image. There is no doubt that a good 100cc kart is still a very fine driving experience, described by Ayrton Senna as the purest form of motorsport after he had won the Formula 1 World Championship. This is something the MAX will never be.

The MAX was not designed as a competitor for 100cc engines, in fact Rotax continued to manufacture 100s for some time after the introduction of the MAX. In many countries the MAX was not affiliated into their national classes and remained in the leisure categories. However market force is the strongest element to make something happen even when the governing body may be at odds with the particular line of evolution. I remember a powerful mover and shaker in the 100cc classes saying that the MAX might become popular but that it would never run in Super 1. This year the MAX classes have easily the highest number of entries at Super 1. The Rotax MAX has evolved over the past seven years from a slow start to such excessive demand that supply just could not keep up. The engine unit has been improved in terms of production quality and consistency but a well maintained early
engine will still perform well enough to win at club level today.

There can never be a win/win situation forever and without doubt there will eventually be something that takes over from the MAX. It may be another Rotax product, if so it will almost certainly be a 4-stroke. However, for the time being the Minimax, Junior and Senior formats are very much here to stay and will be so for many years to come. The long term future may well be 4-stroke but this is a fundamental change for karting and one that will not be an easy transition in my opinion. A high performance 250cc single cylinder engine sounds to me very much like one cylinder of a Formula 1 engine. To be efficient and produce low emissions it must have electronic engine management and fuel injection with the potential to drive costs through the roof.

Design and production of a racing 4-stroke has to be of a far higher standard than a 2-stroke of similar performance, the maintenance costs are also bound to be greater, there are a lot more moving parts. A performance 4-stroke has a high maintenance valve train and there is no escaping that. I do believe it will happen to karting and probably within the next ten years but there will be space for 2-strokes for a long time to come. There are so many people involved in karting today who would never have known about it years ago, simply because public awareness has increased dramatically. I remember a survey during the 1990s. The statistic I will never forget was that 1.25m people a year drive karts in Britain but that only 3% are MSA licence holders, oh dear! Again the MAX scores. So many are used by hobby drivers who have a great time, charging round at weekends racing their mates, but who never aspire to racing officially.

These participants are clearly valuable to the industry. They do not account for 97% of the business since their karts are often maintained to a very basic level, but their contribution is nevertheless significant. I’m sure the majority of this magazine’s readership is the MSA racing minority, the rest are the people supporting the racing fraternity indirectly by providing homes for last year’s racing equipment. This section of the karting public is often overlooked and need to be encouraged to stay in the sport and aspire to participating at MSA level. On the technical front this month, I want to revisit the old chestnut of carburettor jetting.

Those of you who know it all or cannot believe I am about to say the same things again, please feel free to turn to another page. As a result of writing this column I receive a number of telephone enquiries from people in trouble of some sort with their MAX engines. Carburation is by far the most popular subject. Regardless of class the same Dell’Orto 34VHSB carburettor is used but the three MAX class engines all demand a different carburettor set-up. The Senior engine needs to rev up to 14,000rpm, the
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Junior up to 12,500 and the Minimax up to 11,750. These are broad figures and I know plenty of people claim much higher rev values. These are generally accurate figures that don’t allow for revs increasing when leaving the ground or when there’s a following wind on the fastest straight. As a guide you need to see rpm readings within 1000 of the above figures to be competitive. High revs are found by near ideal jet settings. If the jet is too big, the engine will not run clean at higher revs, however if the jet is too small the Junior and Senior engines will pop back through the exhaust and may lack mid range power.

There is usually a reasonable band of jet sizes within which the engine will run satisfactorily, it is also true to say that there are carburettors that react more to small changes than others. The Minimax with its 2004 restrictor in the exhaust only, certainly needs a much smaller jet. For example, an average jet size for a Senior might be a 162, on the same day with the same conditions and a similar carburettor a Junior might run a size or two bigger at 165 or 168, a 2004 Minimax on the other hand would require something between 145 and 150. It is worth reminding everyone that for MSA racing the carburettor must now be completely standard. People are still being caught using non-standard slow jets and needles. Unfortunately rules are rules and they are there to make the playing field as level as possible for everyone, there can be no excuse for running illegal components.

The only part that may be changed is the main jet, the needle may also be adjusted for height. Both the 8.5 and 12.5 venturi models are eligible but others stamped 9, 11, 13 or anything else for that matter are not original equipment and cannot be used. The exhaust must not be ignored, the life expectancy of the baffle tube and wadding is 10 hours, this is easily overlooked and can lead to unexplained loss of power as the inner end of the perforated tube starts to decompose allowing the wadding to implode, partly blocking the exhaust outlet. When fitting the new baffle and wadding I prefer M4 button head bolts with nylock nuts to rivets. It is worth checking the whole exhaust for cracks and damage. It is now acceptable to repair by welding the exhaust providing this does not change the original specification of the system in any way.

The new season of racing is well under way with club and championship meetings into their second and third rounds. The usual cries of ‘cheat’ and ‘foul’ are heard rumbling around the pits, the majority being unfounded but rest assured that JAG do take these reports seriously and expend a lot of time and money ensuring the classes remain as fair as possible. Next month I hope to bring you details of impending Rotax RM 1 test days. Also a look inside a MAX engine after years of trouble free running.

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The Max Column: May 2004

By: George Robinson

Since first writing this column almost five years ago it has sometimes been necessary to go over the same subjects again and indeed to update as the MAX has evolved. There have been reports of poor performance recently and, as usual, the engine gets the blame. In most cases the cause of an unexplained drop in performance is an external malady. The most common is the fuel supply system that starts at the petrol station and ends in combustion. The fundamental element of an engine running properly is the quality of the bang on combustion. I have been caught out by poor fuel on more than one occasion and have sometimes not realised the problem until sometime later. Always try to buy top brand petrol from a filling station with a high turnover. The fuel is likely to conform to the manufacturer’s blueprint and not be a mix of different brands.

Unfortunately, there is no way to be sure that the fuel you buy is good but it is well worth testing the petrol you intend to use for racing. I well remember when unleaded was introduced on the continent, it could seize the best 100cc engines for no apparent reason. Having bought your fuel and mixed it with your choice of best quality synthetic premix oil, it’s worth giving the fuel supply line a health check. Is the pick-up inside the tank in good condition? Because it’s out of sight it’s often out of mind. The tube should be long enough for the brass weight to sweep the bottom of the tank, the tube does shrink and harden with age. Rotax have introduced an in-line filter that is strongly recommended, we have always used the bronze sintered type filter that replaces the bob weight in the tank. Both filters are not necessary but one or the other has to be a good idea.

The Rotax filter has a paper element and will therefore lose efficiency with age and use and should be replaced every 20 hours. It’s always worth renewing the fuel line when it starts to discolour, it does deteriorate and can lead to air leaks at the joints, it’s also handy to be able to see what’s going on inside. If the fuel runs back from the pump towards the tank this is a sure sign that there is a problem in the pump. Neither rebuild kits nor indeed pumps are too expensive. The ideal situation is probably to have a spare pump ready to fit and then you can rebuild
the faulty one at your leisure. These pumps are more than capable of delivering enough fuel providing that they are in good condition. If their efficiency is impaired they lose a lot of performance and can give very strange symptoms. So often the pump is forgotten as a possible source of trouble. The fuel may well run back from the carburettor towards the pump, or appear to do so. What is actually happening is that the fuel is draining into the float chamber that is less than full with its needle valve open. If the float chamber is full then the tube to the pump will remain flooded.

This is why it is always a good idea to blow the fuel through before trying to start the engine. The engine will start more easily if there is plenty of fuel on demand, this will also eliminate the long periods of cranking required to pump fuel through on pulse at cranking speed. The carburettor is another area for attention. If the fuel filter has been used then dirt should not be a problem, however it is the first thing to check. Just below the brass fuel inlet tube there is a 12mm aluminium nut and behind this is a small plastic filter. It must be spotlessly clean and in good condition. If there is any sign of dirt here it is advisable to strip the carburettor down and give it a thorough clean, the problem being that this small filter does a good job of catching the grot and stops it from reaching the needle valve until you remove it from the housing.

Then some of the dirt is brushed off the filter and is left in the fuel way ready to be washed straight into the needle jet as soon as you blow the fuel through. If the internals of the carburettor are a bit too daunting then it’s a relatively inexpensive overhaul at the local service agent. Now that carbs have to be in completely standard form for MSA racing it may not be a bad idea to have your agent check it in any case just to be sure it conforms. Having worked through the fuel system and providing you are not a mile out on the jetting then you should be able to eliminate this area from your enquiries. The electrical system is also equally ignored as a source of trouble. To trace the electrical system start at the battery. The battery as supplied is very reliable and is even better since the introduction of the new foam pad and top-securing strap. The old plastic cover did a good job but was sometimes awkward to fit and prone to cracking if not treated with respect.

The wiring loom is very simple, the black wire is the negative or earth side and runs straight to the engine and should be secured to the engine not the coil. The second thin black wires provide a neutral to the ignition pick up and the coil, these should also be secured to the engine. The thick black wire is for high tension and is required for spark and starter motor. The thin wire is low tension, needed to complete the circuit to run the ignition pack and crank sensor. Dead simple really! The red wire from the battery is for live feed and only needs to be thick to run the First in the World for 44 years high tension starter motor, the rest of the ignition runs off the thin wire to the on/off switch.

This switch incorporates an automatic fuse, that’s why it may seem expensive for what it is. It is most important that this original switch is retained, the fuse is there to protect the rest of the ignition system, it is also illegal to substitute another part as it would not be as supplied by Rotax and thereby outside the MSA regulations. The loom must be kept in good condition and checked for damage and cleanliness on a regular basis. The coil or ignition pack to give it its correct title is usually very reliable, the most common cause for damage is the incorrect fitting of earth wires. If these black wires are fixed to the coil side of the rubber buffers and there is any problem with the short earth strap the coil will be destroyed. Fix them as previously stated to the engine side and you don’t even need an earth strap. The starter motor needs to be properly looked after as detailed in last month’s column but since the repair kit has been available there have been a lot less failures. Prevention is always much better than a cure.

On Senior engines the power valve must be regularly checked and cleaned. The amount of carbon build up will vary according to the oil that you use but serious competitors will strip and clean their power valves after each meeting. The symptoms of a sticky power valve are lacklustre performance and power that comes in with a bang. An inoperative valve completely kills top end and the engine will not rev, very easy to diagnose.

The exhaust should be trouble free providing it is not ignored, the wadding should be changed every ten hours and it is probably worth replacing the baffle tube at the same time. I prefer to install the new tube with bolts as opposed to rivets, only because it is difficult to get rivets as good as the originals and these repairs have been known to fail. The nut and bolt option can look very neat and is completely safe if done properly. The problem with the new style CIK bodywork goes on, the general guidelines were well covered in last month’s TKM News column but the problem for MAX is that the CIK have decreed that the pods may not be cut unless to accommodate a JICA type starter.

This leaves the MAX with a problem on some karts with some types of bodywork, It is best to check with the chassis supplier before buying the new type pods. In some cases it is certainly possible to mount the engine slightly closer to the seat or introduce spacers between the engine and mount in order to raise the engine just enough for the radiator to clear the pod. The Clay Pigeon warm-up race meeting at the end of February was a fantastic success, all three MAX classes were very well supported. Some good clean racing was had by all, the atmosphere was great and it was dry as well, a cool breeze the only thing to spoil a great weekend, I found a good spot out of the wind by standing behind Ian Rennison!

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The Max Column:February 2004

By: George Robinson

The MAX Column has been running for four and a half years. During that time much has changed and a lot of MAX engines have been sold to every kind of customer. The British Isles remain firmly at the top of world sales along with France and Australia. Over 5,000 engines have been sold to date in the JAG distribution area of Britain and Ireland. Of these approximately 3,500 are Senior engines and the balance is Junior. JAG was the first distributor to introduce sealing and the system has been highly successful, so much so that Rotax have adopted the same type of seals and supply them to their distributors all over the world. Every engine that comes into this country is fiche checked and all the records are kept on file for future reference. John Gravett, who put the ‘G’ into JAG, personally checks every single engine and so has a very good handle on the consistency of the product as it lands here from the factory. I know that now, after almost six years of Rotax MAX, there are rumours of complacency.

Nothing could be further from the truth, in fact the standards of engine service and maintenance have continued to improve since the agents were accepted and the majority have had an audit visit. The purpose of this is to ensure that the dealers have adequate equipment to carry out rebuilds to a quality standard that will prolong the life of reworked engines and at a consistent level of performance. There are now in excess of forty approved service agents and they have all agreed to rebuild engines within the bounds of the official fiche and stand the ultimate risk of being struck off should they fail to do so. Provided that they have made the necessary investment in measuring equipment then the fiche checks are relatively straightforward. Sealing agents having made their commitment to the servicing of Rotax engines do deserve the reward of a consistent number of rebuilds coming their way. The current feeling seems to be about twenty to thirty hours for a Senior engine and more than that for Juniors or Minis. In fact I have recently heard of a Minimax that was rebuilt at sixty hours and looked as though it had just been run in.

No doubt the Minimax with its heavily restricted output has a very easy time of it in terms of stress on the 26 internal components, already super reliable in the Senior engine which produces just short of double the horsepower. The new Minimax restrictor is now available. After much testing and discussion to find out what was really required by the MSA and the other powers that be, sanity has finally won through. The new exhaust restrictor has an exit bore diameter of 20.3mm and no inlet restrictor is required. This will benefit the class considerably in that it has a couple of advantages over the old system.

Firstly, by doing away with the inlet restrictor this will greatly reduce the risk of icing in cold or high humidity cold weather. Secondly, I believe the engine will be easier to manage in terms of jetting and the jets are likely to be smaller than we are used to, probably by two or three sizes. The official wording of the new restrictor regulation is “Confirmation Regulation B4.4.2 Restrictors. Exhaust Restrictor Only, No Inlet Restrictor required.

Exhaust restrictor must be in place at all times. Restrictor must be as supplied by JAG and comply with the official fiche, no modifications allowed. Exhaust flange restrictor 20.3mm maximum round bore. All exhaust gases must pass through this restrictor”. That’s it. It’s really very simple to fit, equally easy to police and impossible to modify without risking detection, a win/win situation to further enhance this highly successful class. The carburettor must now be standard in every respect, the only part that may be changed is the main jet.

There is only so much you can do to make a carburettor work properly, so the wild claims about massive power increases should be a thing of the past. The principal causes of carb faults are dirt and incorrect float heights. From now on the Rotax supplied in-line filter is not only allowed but also recommended. This filter should be changed at least every twenty hours but this of course is a general rule and is entirely dependent on the cleanliness of your fuel. The filter is clear material plastic and so should be easy to see through and get an idea about its condition, if in doubt chuck it out and fit a new one. There will some significant changes to the MAX International Challenge format and the finals themselves.

There will be a full series of races for Juniors and Seniors, with at least the best of each winning the dream ticket. At this stage it is anticipated that Juniors will have all their equipment provided for the World Finals. The Seniors, having competed on their home turf on their own MAX equipment, will arrive at the (as yet secret) destination to race the Rotax supplied RM1 karts. Now this I want to see! In countries where there is RM1 racing taking place, I understand that they may also be able to race for a place in the World Finals. Here in the UK there has not as yet been enough interest to run anything more than demonstration races with the RM1, however the news is good because JAG are offering test drives free of charge to interested parties. So far it looks as if there will be at least four venues where anyone with a degree of competence can come and have a go. If you think that might be for you but are unsure whether you have the experience, I can promise you that the RM1 is dead easy to drive and you don’t have to try to break the lap record in your first couple of laps.

JAG also has two Senior MAX test karts which I believe will be made available for the less experienced to acclimatise themselves. This has to be a great opportunity to try something a bit different. For those of you not sure what the RM1 is, it’s an automatic adrenaline machine. It has a two speed gearbox with a steering wheel mounted paddle shift. The engine looks similar to a Rotax MAX but in fact has a slightly uprated cylinder barrel producing around 32 horsepower as opposed to the MAX that gives 28hp. The gearbox is integrated within the engine’s main cases and is directly behind the crankcase. The rear axle passes through these cases and is driven via a spline which has a flexible fixture onto a hub. The kart has a four wheel brake system with self adjusting split hydraulics front and rear that also have a bias control that can be adjusted on the move.

There are many innovative features on the RM1 that make it unique in the world of karting as we know it. If you would like a no obligation test and to have a closer look `hands on’ then please contact J.A.G. on 01892 611805 or by fax on: 01892 611806. Alternatively you can email me at At this time of year I know I’m right in saying that for many of us, karting and the thought of getting out into the workshop to do any maintenance come a fairly long way down the list. Unfortunately, without some attention now, our trusty karts will not be so faithful when the first of the spring weather comes. Please, first of all, check that the engine has antifreeze in its coolant then make sure that the fuel is completely drained. Any residue turns to glue and can completely ruin the carburation to the extent that the engine may refuse to start until the carb has had a specialist rebuild. If possible keep the kart somewhere dry and not too cold.

Tyres also benefit from not being left out in the cold. Only you can judge how much of your karting equipment you can cram into the cupboard under the stairs before you yourself get banished to the shed at the bottom of the garden. So far the 2004 season looks really exciting for the Rotax classes and lots of new ideas and opportunities to go racing has to be good for all. I will try to keep the news coming and try to keep it interesting. If anybody has a topic they would like researched, aired or printed please contact me direct at the email address above or via the magazine.
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The Max Column: January 2004

By: George Robinson

Iis cold and it’s wet so we know it must be about time for the International Kart Show. The second year at the new Telford venue was a great advert for the health of the British kart industry. I believe there were almost 70 exhibitors and there had been a lot of effort expended to put on a really good display by all the big movers and shakers in the trade.

It’s good to see intense rivals chatting the breeze both at the show and into the small hours in the bar. Some people’s dedication went far beyond the call of duty and recovery can be long and painful. Once again the show produced a huge variety of chassis built for the Rotax MAX with versions for Minimax, Junior, Senior, Promax and endurance racing.

I know many of the exhibitors achieved sales during the show and others, while not having taken firm orders, have good strong leads to follow up. This new business is very encouraging for the coming season because the majority of new sales will be for racing. These competitors’ used equipment will then go on into the after market at a lower price that helps to attract the newcomer or those on a tight budget.

Used equipment can be very good value and there is now enough of it around to keep the prices keen and the quality up. If you see a secondhand outfit that takes your fancy but you are perhaps unsure of the age or condition of the kart or engine it might be a good idea to contact your local MAX service agent who should be able to age the engine for you and give the whole kart a bit of a health check. As I have said before, the engine identity card does give you a guide to the service history but cannot be used as proof of its current condition.

If the engine has just been rebuilt and not run then the card will prove the date and the agent who sealed it, he should be able to confirm what parts have been fitted and why. If the identity card is not available the owner should find it or apply for a new one before you complete the transaction.

This will give you a degree of feel good factor about the engine’s provenance. From January 1st the carburettor must be in standard form and can only have 8.5 or 12.5 venturis and this is another area to be checked. The idle jet and emulsion tube must also be standard and both marked ’30’. Any carb modifications are strictly forbidden and of course they are one of the easiest things for the scrutineers to look at.

Although I do believe there are some super deals to be had on secondhand kit, it can be a real minefield so please beware that you are not doing the old classic of saving a fiver in order to spend a tenner. Spares and repairs can be expensive so try to buy something that needs little or no work. One major advantage of buying privately over a dealer is the saving on VAT. Then again with the dealer you should have some come back if things go wrong.

There are some new exciting plans for next season. Rotax have encouraged their distributors to run a Rotax Eurochallenge following the success of the Austrian distributors’ Eurofinal over the last two years. The Eurochallenge will be held over four rounds in Italy (5-7th March), Holland (29-30th May), Austria (30th July-1st August) and in Spain at the end of October. The classes will be for Senior and Junior MAX and the RM1.

The Rotax MAX Challenge rules will apply for the Eurochallenge, however an MSA National A licence would be adequate and drivers are responsible for their own expenses at these events. The prize in each class will be an all expenses paid entry into the next World Finals courtesy of Rotax. Closer to home, the new 175 Senior class has had a major boost in that it has been adopted by the Super 2 and will run within their championship meetings during the 2004 season. They have a good selection of venues across the country.

For more details contact Roger Abbey-Taylor at Ratpro (email: ratpro@btinternetcom). This is good news for the slightly better fed among the finely tuned racing drivers in the MAX ranks. Also another challenge for the Gentlemen’s Challenge boys who had such a lot of fun last season.

These guys have really got the right attitude to their racing, they are there to enjoy themselves and have a good race too. Anyone who finds the regular weight limit of 160kg a little hard to reach should seriously consider the Gentlemen’s Challenge or the National series as a whole. This must be the final column for this year so I wish you both a very happy Christmas and a successful New Year whatever class you support.
The last round of the 2003 Dadson’s Gentlemen MAX Challenge took place at Lydd on the 9th November, with 3 drivers up for the championship. It started to rain, which gave all the drivers something to think about. Heat one saw Kevin Gilbert on pole from Graham Fagg, Tony Cowlam and Martin Cull and it was Gilbert away with Cowlam on his bumper.

Fagg dropped back and so did Cull, but the two championship leaders were fighting their way through from the middle and the back and by half distance Melvyn Francis and Nigel Ward were up to 3rd and 4th places. Kevin Otway was up to 5th, but with a coming together with John Holmes he dropped back to 9th. At the flag it was Gilbert the easy winner from Cowlam and Ward. Heat two saw Otway on pole from Gerard to the editor

Sir, I would like to thank the CRG Team for all their help and support over our 2003 championship season. I would also like to extend my thanks to the guys at Maxter who put in many hours behind the scenes. Obviously I can’t thank everybody that lent a hand or gave me some advice during the year but they know who they are. However, there is one influential person whom I can’t
express enough thanks to. I am extremely grateful for the help and support that Terry Fullerton gave me throughout the year, his experience was invaluable and I know that this win would have been impossible without his help and support.

I hope that Terry enjoyed working with me as much as I enjoyed working with him, his knowledge within karting is exceptional and fundamental in my development over the past season. Yours in karting, Wade Cunningham, 2003 World Champion
Dray and it was Otway clean away, controlling the field, with Dray dropping back and Ward flying into 2nd by lap 4. At the rear it was Francis on the move, with Cowlam following, but as they came across Bent, who seemed to be struggling for grip, they touched and spun out, allowing the field to close up. At the flag it was Otway from Ward and John Beckenham.

The final saw polesitter Ward away and with Cowlam sticking to him like glue Gilbert could not slip in. At the second chicane Ward’s engine stopped and Cowlam had nowhere to go but into him and with that Gilbert took the lead, with Cowlam and Francis 2nd and 3rd. Francis made a move for 2nd place but did not quite make it and spun out, leaving the door open for 3rd which Otway took. Gilbert was the victor, with Cowlam 2nd and Otway 3rd. Report Tony Cowlam
Final championship positions: 1 Melvyn Francis 388 points, 2 Nigel Ward 371, 3 Winston Bent 351, 4 Kevin Otway 323, 5 John Beckenham 310, 6 Kevin Gilbert 282.
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