Hi all, I have a 48cc spitfire/starfire/grubee/skyhawk engine mounted on a mountain bike.
I've only put about 50 miles on it, I'm still breaking it in, but today it failed. I went about 2 miles on it and it started to loose power. I stopped the engine, and it won't start up again. I have spark, fuel flows freely into the carb. I believe the compression is OK (I can pull the plug, cap it with my finger and release the clutch, and when I push the bike forward I can feel the pressure).
The plug was very dirty, since I'm still breaking it in and it's using a higher oil:gas ratio, so I put another one in to test. It gets spark if I pull the plug and hold it against the cylinder head. How do I tell if the spark is weak?
I pulled apart the carb, it looked very clean, but I sprayed it out with an air can anyway. Spark was gapped to 0.038", then I tried it at about 0.032". I don't see any blockages in the exhaust, but there is fuel and oil practically dripping down the exhause tube, so I don't think it is combusting. It's hard to tell by the noise when I try to pedal-start.
I pulled the cylinder head off, and I don't see any damage to the cylinder wall or piston. The piston has a fairly thick layer of carbon/oil on it.
Any random tips would be appreciated.