so I have a cm250c, 82, that the wife rides. now I have cleaned the carb, adjusted the valves and cleaned the electrical connections. all this was to solve this problem...... when I start it up cold it runs on one cylinder. if I keep giving it gas it will start to pop and sputter and once it gets warmed up will begin to run on both cylinders. the one that was not firing will smoke like hell for a few minutes, I can only assume that it is because it has a lot of unburned gas in there... any ideas what this could be? stator, cdi unit, coil?? any help is appreciated. the hurricane is about back together and I want this thing ready to go for her when I am ready to head out! another note is that it ran fine last year...

 

it just gets better... I swapped the plugs around to see if the problem followed the plug and now I have a stripped plug hole on this old beast. plug still goes in but it is loose. helicoil time I suppose. or it is time for me to start getting my sh*t together and get the old cb750 going instead lol!

 

Ya, helicoil is probably your best bet. your approach is what I would have started with as well by swapping plugs, or a whole new set of plugs. If that doesnt help, its gotta be in the carb. I wouldnt think it would be in the cdi or coil, generally, if either one of those are bad, it will not spark at all or be so weak, it will never clear out the gas in the cylinder and just run on one cylinder. there are cases where the cdi and or coil are weak and cause an intermitten problem, but those are generally once the bike is warm, not cold. But anything is possible, but more times than not, this is the case.

a call around to local salvage yards may yield a used head instead of helicoiling that one. But a helicoil is an ok alternative too. Personally, I prefer to use keyserts. they are designed to not back out. here is a link to them if your not sure what they are.

http://www.newmantools.com/key.htm

I dont know if its time to get out the 750 yet.. perhaps its time to turn over the Hurricane to her and treat yourself to a newer 600 or ???

 

well I can't get a helicoil for it, it is a TINY plug with a 1.0 thread I guess?? the guy at fastenall (they KNOW bolts!) said that a good alternative may be to find a slightly different plug that is bigger but with the same heat range and length. anyone know how I do that?? and I would get a newer bike, but the new baby dictates that I not spend a lot of $$ on one lol!!!