The Classic Motorcycle
A few months ago, I filled five litres of branded synthetic horticultural two-stroke fuel into my 197cc Villiers-engined FrancisBarnett Falcon to avoid using pump fuel with five or 10% ethanol. The bike ran well and seemed to perform better than on pump fuel mixed with oil to create premix.
Pulling it from the garage after the last winters, I filled another 5 litres of the twostroke horticultural juice into the F-B. It ran well for about 12 miles and then the engine locked solid when cruising at about 45mph. Once cool, I rocked the engine free – as I guessed it was a piston seize – and pottered the six miles home, very slowly.
Save a few seize marks on the piston skirt, I seem to have got away with this excitement. Why did this happen, and is the horticultural fuel unsuitable for my bike’s Villiers 8E engine? Please don’t identify me as I think I must have done something stupid! Len R, Kempton Park autojumble chat.
While I don’t publicly recommend such fuels as you have used Len, due to my doubts over the legality of what I’m doing taxation wise, I have used similar in all my machines for more than a year with 100% success. They start much easier, appear to perform better and are a bit more economical – the downside is that such fuels cost £19/20 per five litres.
Your seizure has, I think, nothing to do with the fuel itself, but rather its oil content, as you are buying it as a premix two-stroke fuel. Reading the information sheets confirm it is a 50:1 (50 parts fuel to one part synthetic two-stroke oil) mix, ideal for two-stroke buzzsaws, strimmers, hedge trimmers et al, but not your FrancisBarnett, which needs its premix making at a ratio of 16:1. This morning, I went for a 25 mile ride on my Villiers-powered trials bike with its premix comprising 16 parts of horticultural four-stroke fuel to one part Castrol SAE 30 mineral oil.
Some claim premix made with the branded horticultural oil is unsuitable for our older two-stroke engines… I’m not arguing this, but can report we’ve used it in a range of British and Continental twostroke machines with total success over last 18 months.