Thanks GRUMPY for your reply, and your thoughts on half crank engines. The line trimmer I'm talking about has 34mm bore and about 30mm stroke, straight shaft and the dreaded half crank. It'll have to do cause it's the only one I own. Which grommets do you recommend for the fuel lines, is imitation rubber impervious to petrol? With the guard I might have to make one out of polycarb. Cheers Wassie