Hey guys, i just about a year ago rebuilt the engine on my CB125J from 1977, i wasnt a complete rebuild but it got a new cylinder sleeve and piston with some other parts. Never the less it ran perfectly until about a week ago, when i gave it a bit too much throttle and the valve to rocker arm adjuster tappet somehow unscrewed it self and fell off. The screw and nut thankfully didnt do any damage to the cam or any other parts, so i just put it back into place and adjusted the clearance (0,05mm). Assembled the entire thing and it started right up.

So to get to the problem; whenever i start the bike up, it starts no worries, but whenever i get to around 6000rpm it starters stuttering as if it doesnt get enough fuel. But the carbs havent been adjusted at all since they ran fine before the "accicent". So the things i've checked and adjusted:
- Rocker to valve clearance (0,05mm)
- Breaker point clearance (0,35mm)
- Ignition timing
- Checked the timing advancer, everything moves and is greased properly
- Carb jet, same size as before and is clean as is the rest of the carb

I dont know what is wrong, but i've checked all the parameters that i touched during dissassembly and assembly.

Thanks beforehand.

 

I owned one just exactly like this one...same color too. It was my second bike in the 8th grade. 1969 model...





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