Originally Posted by
Mosser
I thought i would take my 1982 Honda CM125 out for a blast today, it started out running nicely, and could reach 65-70mph which is what it has always done, but about 30 miles into my ride, it started to loose power and was backfiring on 1 cylinder only whilst i was doing about 60 and i lost power and it slowed down to about 30mph, when it suddenly picked up power (the other cylinder kicked back in) and it took off again.
It continued to intermittently run rough all though my 80 mile ride i did today, and at 1 point when i stopped at a roundabout, the left cylinder cutout completely and when i gave it even the slightest bit of throttle, it would splutter and backfire and put out blue smoke from the left cylinder only.
The right cylinder seems to be fine all the time, but when the left cylinder cuts out, it coughs and smokes and backfires for a minute or 2, then clears itself up and runs perfectly on both cylinders again.
I have had this problem for a few months now, but never this bad, I recently fitted new spark plugs and a new HT coil and leads, it had all fresh petrol today which it ran fine on for the first 30 miles, so its not the fuel thats the problem, I have recently cleaned the carb out with carb cleaner and its spotless inside and showed no signs of wear on the slide or needles or jets, the float height is spot on and the mixture screw is at the factory recommended 1 turn out, i did try half a turn either way today, but it didnt help, and i dont think its a carb problem anyway as the right cylinder runs perfectly all the time, and i have had a spark checker plugged in when the left cylinder has been cutting out and it was showing a nice fat spark so i am now out of ideas as to what could be wrong ?
Has anyone got any idea about these old bikes and what i might do next to diagnose or solve it ?
Thanks
