Expert: Bill Silver - 11/3/2009

Question
Hey bill, you seem like the most credible guy on here to ask a question about this thing. Ive had it for about 3 weeks now. at the start it had a wiring problem and would not start. my old instructor had a 200 model sitting in his garage that he gave me to mess with hooked after a little tweeking it ran but it ran really choppy when there was a load on it. so i switched to the 250 with the 200 harness and i got the same problem. i have to clue what to do to make this thing run the way it should. please help me

Answer
Sean, misfiring under load problems can stem from several causes.

I guess you know that the ignition is CDI, so not adjustable. Pretty much works or it doesn't, however the CDI modules can fail and give erratic output. You need to put a timing light on it when it is running in neutral and see if the timing advances as you rev it up. CDI ignitions are self-powered, so don't need the battery to make sparks. The battery is a load for the charging system output and a dead, dying or missing battery will cause the charging system to go full output and fry light bulbs and other electrical components. I would check the spark plug caps for 5k ohm resistance values and use fresh spark plugs.

IF the bike was sitting for a long time, the whole fuel system needs cleaning from gas cap to float bowl. If the bike has had mods to the intake or exhaust system, the OEM carb jetting calibrations may not work now.

Make sure that the valves are adjusted and compression readings are around 150 psi or more.

http://www.cmsnl.com/honda-cm250c-custom-1982-us_model1045/partslist/ for parts references.

Bill Silver