Thursday I bought a ryobi trimmer from a craigs ad. They wanted $70 but I pointed outthat they had premix in the fuel tank and that the oil was in the crankcase. Thankfully there was oil in there and I got it to start in the cold w/ premix so I offered them $50 after the cloud of smoke cleared. There was no permanent damage. I dumped the oiled gas, cleaned the plug and ran it on straight Seafoam for about 10 minutes. I dumped the Seafoam except what was in the primer and lines, then filled the tank with 91 octane (best available from normal stations 10%methanol) I pumped the primer several times to clear the seafoam and mix it back to the tank. As I run it more the smoke is completely gone!
Its only 26.6cc and weighs about 13 pounds in working string trimmer trim. I hope the motor and clutch could be 7-8 lbs. It turns the head smooth and strong to ~6400 rpm according to a multimeter. I think it sparks on the exhaust stroke and the bang, don't know yet. Should be a fun toy. I'd like to build a front wheel drive 26" streetfighter type of hybrid. I'm tired of fighting my happytime chain tension problems. I might buy a GEBE front kit or buy a welder, teach myself some welding and build my own jackshaft drive. GEBEs cost about the same as a good 110v welder and jackshaft parts. Hmmm.
Check the used equipment ads. I got what was a $225 machine for $50. Its a sweet little motor. According to the manual it should turn 8k and make 1bhp. That's optimistic but this should be fun. The manuals are free PDFs. The sparkplug contains unobtainium and costs $5.