The heat of the summer is upon us and can take both man and machine by surprise. Most of us enjoy the warmer weather and here are some tips to ensure your Rotax enjoys it as much as you do.
From the Rotax Max engine point of view, an engine in good condition will easily withstand any heat the UK weather can throw at it. The ideal working temperature for all classes of Max is between 50 and 60 centigrade. If under extremely hot conditions your engine exceeds this, there is really nothing to worry about from a reliability standpoint. In hotter Mediterranean or Middle Eastern countries engines frequently run at 80 + degrees with no ill effects. It’s true to say however that the cooler you can keep the engine in hot weather the better the carburetion will be. The engine needs a good core temperature to get the exhaust gas temperature up to efficient levels. This is why engines don’t always perform equally when the time from pits to racing is very short.
Most engine builders will fill serviced engines with coolant mix. The most basic type is usually blue, this gives perfectly good frost protection and a basic level of corrosion inhibitor. The better automotive coolant is pink which gives a higher level of corrosion protection and is better still for water pump lubrication. Unfortunately both these types of anti-freeze don’t help the engine run cool. Plain water will definitely run cooler than anti-freeze, distilled or de-ionized water will run cooler still and has a less acidic effect on the internals of your engine. All good news then? Not quite, first you lose the lubricity of a good coolant and second you must remember to drain and refill the system before frost. There are also coolants that enhance cool running. This can be a win-win situation as some of them also provide adequate frost protection as well. These coolants are usually more expensive than regular types. A couple of brand names to look for are Ice cooler, which is green and Water wetter which is pink. Before using these products read and adhere to the insructions.
In very hot weather there are other areas that come under extra load such as transmission and gears. It is generally true that hot weather brings more grip to the circuits and so the chain and sprockets need to be in as new condition and well lubricated. Since the introduction of the clutch O ring there is very little evidence of grease getting into the clutch. If you want to be sure, take the drum off, clean the inside with brake cleaner, put the smallest smear of grease on the inside of the sprocket bore and re-assemble having checked that everything is dry and clean. While the chain is off lubricate it well with a high quality chain lube and allow the propellant to burn off before refitting it. This will ensure good lubrication for the duration of the race and cut out the risk of a scrutineering issue with a wet clutch. Only chains and sprockets in perfect condition provide efficient transmission. People are always searching for fractions of a horsepower and then fit used sprockets and chains that rob ten times that amount.
It is worth experimenting with a richer fuel/oil mix. The Rotax recommended 50:1 or 2% is adequate for engine reliability but a mix of 3 or 4% can help to keep the engine cool and constant for the whole race. An interesting by-product of this is that the carburetion also becomes easier to jet. As a matter of good maintenance, check and change the gear oil frequently. The recommended service interval is five hours. Why not check it before each race meeting? We’re always surprised by how many engines come in for service with very little oil in the gear-case. Most customers admit to not checking it since the last service.
In hot weather the largest single loss of performance is within the driver! Stick with cool mineral water. When you realise you desperately need a drink, it’s too late; you’re dehydrated. Continually sip water and take a good couple of mouthfuls before putting your helmet on to race. It’s a good idea to leave a small gap at the bottom of your visor which will allow a little cooling draft to keep you alert. Don’t forget your helpers need fuel and water as well!