The Max Column

The British show season is now firmly behind us and we can now look forward to the days lengthening and the start of some serious racing without the need to freeze your extremities off. The first all-MAX meeting of any size this year will be the Clay Pigeon Winter Warm-Up over the weekend of the 25/26th February. This event has been well supported over the past couple of years and has every probability of being even stronger this year since the first round of the Rotax Super 1 is at Clay at the end of March. Although entries are still open for the Super 1 Neil Hann reports very strong registrations in all classes. The MAX is very much alive and well. There have been some drivers out testing the new Vega SL6 although some have been disappointed that they are not instantly faster. The new tyre was never expected to be substantially faster, however it is a better design and will remain consistently fast for many more laps than the outgoing SL7. As ever it is up to individual driver’s chassis setup to find the best tyre pressures to suit. I believe it is best to start with low pressures and find how quickly you can get the heat into them and thereby achieve your fastest lap early enough without the risk of the tyres overheating and tailing off too soon.

If tyres are seriously overheated their performance may well be damaged forever and, in spite of an electric start to the first heat, you will have seen the last of that level of performance from those tyres for good. A serious mistake as it is only the winner of the final who gets remembered! In a change to the airbox regulation it is now permitted to drill a hole in the underside of the bottom casing. This hole must not exceed 8mm in diameter and must be drilled through the central injection moulding mark. I think it should be safe to use a 7.5mm drill bit. Do not be tempted to use an 8mm bit, it will almost certainly drill oversize and some scrutineer will pull you up on it. There have been some reports of carburettor icing and unfortunately this is something that afflicts all sorts of competition engines in cold and humid weather. The icing is caused by cold, humid air being drawn into the engine at high speed, the wind chill is so great that the airborne water droplets freeze and adhere to the inside of the venturi in the carburettor. This usually starts at the narrowest point in the venturi where the air is under maximum compression. The only hope of improving the situation is to try to raise the temperature of the air going into the engine. Try blanking off the airstream between the side pod and the airbox and cut a number plate to fit behind and below the radiator. It is worth running the engine at a slightly higher temperature than you would in summer.

AUTOSP49
No wonder George thought it was a good show

Although this will not particularly help the icing problem it will help the carburation, especially at the start of a race. The JAG Engineering stand at all three UK shows was very busy and at Autosport International the stand was right in front of the entrance to Hall 20. Although this hall was quite a distance from the show’s main entrance, there was still a tidal wave of humanity each morning as the show opened. After the initial rush there was still a constant flow of enthusiasts right through until well after midday. This year there were some very sensible enquiries and a lot of overseas visitors. You can always tell if a show is good when the time passes quickly and the only day that seemed a bit slower was Friday. The weekend was manic but without too many tyre kickers, so on balance a good show and particularly interesting for the Rotax factory representatives who were on hand to deal with the international visitors. The most common questions from all the shows refer to the carburettor as they always have done. Carburation in karting has always had the reputation of being a black art. Unfortunately there is an element of truth in this and it would be quite wrong of me to pretend that all carburettors are the same.

However it probably is true to say that the vast majority of carbs can be made to run properly and it really is the exception that proves the rule when you find a carb that simply will not work. In this case it is possible that there is some malformation in the casting and that it can never be right. Usually any poor performance traced to the carburettor can be rectified by careful disassembly, cleaning and rebuilding. The carburettor is a mass produced item which starts life as an adequate but relatively low grade casting. It is easy for a small amount of swarf to be left behind in the idle circuit or even under the inlet needle. This will play havoc with the carburation and it may be impossible to ever get a reasonable set-up. The tendency then is to become completely lost with jetting and the other setting to the extent that the situation is made much worse. If in doubt, either strip the carb down yourself or take it to someone you trust for a complete rebuild. Then go back to a standard base setting and start again. If that doesn’t work, sell it! I can’t believe I just said that! A lot of people in all classes are now running at less than full throttle and in the Minimax and Junior classes I would say that the practice is more or less universal. In Seniors there are some who like the flexibility of having full throttle available to them but seldom use it on the straights and others who prefer to nail the throttle pedal and have the best compromise on performance through the range.

This will also vary according to the circuit and the driver’s individual style. One thing is for sure though, it is vitally important to feed the throttle open. Snapping the pedal to the floor does not work, it is essential to match engine speed to how you open the throttle and if using full throttle opening to then back off the pedal to achieve the cleanest, leanest burn. This will give you the highest rpm on the straight and therefore the highest speed. Personally I like the flexibility of having full throttle available, it is good to give it all the fuel sometimes coming out of the fast mid range corners. That is only a personal opinion and may not suit everyone. I am only right nearly all the time! There have been a mouth-watering array of new karts homologated this time and most of them are now developed with the MAX and the forthcoming international TaG classes in mind. Rotax is the biggest class internationally and looks like staying that way for the foreseeable future. The chassis manufacturers are now producing bespoke karts for the MAX and these are equally suitable for all the classes in this country from Minimax through to Seniors and Heavy. There may be an argument that the 177kg sportsman might like a stiffer frame than an 11 year old miniman but the karts have all gone back to a softer more classical design. As usual everyone will be talking about ‘release’ although I am quite sure that half of them won’t know what they mean. To get out of the corner well you have to go in properly. Fact. Unless of course you have a tyre or power advantage over everyone else, in which case it can be a lot less important.