OH NO, YET MORE ETHANOL

I read the interesting comments in RC about fuel. The ethanol fuel thing has been an issue with classic race bikes for some time now and we used to get around it by cutting 97 octane unleaded with 100 LL Avgas (approx 97 octane RON) – possibly a bit illegal. However, there is now a company in Stockport making all-British race fuels with no ethanol at all in them. I’ve been using their 107 (minimum) octane Supreme and this could be used to legally cut 97 unleaded so that if there was any ethanol there it would be disappear almost to nothingness.

The 107 also contains all the good stuff for valve seats and burns very well indeed giving a properly perky engine power.

I ride my bikes equally in UK and in France. Of the two, France is preferable as the roads are better and less crowded and for the most part their general attitude to motorcyclists is much better than in the UK. In the UK I usually just fill up with the cheapest unleaded, 95 octane, as it is the most easily available. At the moment it’s E5; 5% ethanol. Normally I don’t have any problems with the bikes as long as I retard the ignition slightly, and use an additive to stop the carb gumming up and the fuel going off. Even when warm, my 1956 Triumph Tiger 100 with its monobloc carb is a first or second kick starter. Likewise, my 1959 Morini Corsaro 125 and the other older vehicles I own.

Ethanol in UK petrol is likely to increase to 10%. In France, ethanol is already 10% and sometimes 15% (I have seen a pump with 65%...), the bikes run better when the ignition is retarded a few degrees. This results in reduced pinking. On the bike which has manual advance/retard, I only put it onto full advance when the engine is running at more than 3500rpm which equates to about 55mph in fourth. By adjusting the timing while running, you can tell when the engine is smoothest or happiest (not that a mechanical object can be happy or sad: discuss!). Electronic ignition has more of a gradual ignition curve right through the rev range, whereas the old school bob weights and springs fitted to most 1950s and 60s bikes bring full advance very early in the rev range, especially if the springs are a bit weak with age.

On French petrol, when the bikes are warm they can be hesitant to start due (I think) to the way the fuel seems to evaporate from the hot carb. When cooled they are back to normal starting, so I try for short stops at the top of hills. Freewheeling for a while and then putting the bike into gear starts them up again without bother. The carbs have insulating gaskets of Tufnol to reduce heat transfer. This leads me to conclude that the fuel evaporates so easily it cannot be good for the ozone layer – despite the ethanol being ‘renewable’ energy.

I think the effect only occurs in carburettor machines as in fuel injection the fuel is in a sealed circuit. It would be interesting to hear of others’ experiences and conclusions. Stu Thomson, member 2256