You want to make sure that your engine sprocket is in line with your drive sprocket, keeping the chainline straight. I use a steel rod laid accross both sprockets after the rear wheel and motor are in place. If they aren't in line you will be more apt to throw your chain. On one of my bikes I have some wheel rub, now I'm sure this will raise some flags, but I let it rub and it cut its own uniform grooves into the tire and now it runs great...Kelly

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I'm racin' Spitfire, turnin', poppin' wheelies, burnin' evil chasin' pop,pop, pop,pop,pop.... (The Pixies-Tony's theme)