Bonneville America Forums Forums Technical Forums General Tech 81 CB125 running problem

Not sure where to put this... but if it needs moving no probs. I restored an 81 CB125S recently. Took it out this eve for a good and proper road test. After scooting around in hot weather it died. After it sat a few minutes I tried starting it... first kick and away she went. Then... it died again. Let it sit... first kick and we're off. Then... it died. Let sit, first kick, vroooom. I made it home.

So the question is... what could be causing this? Seems a lot of you guys are pretty good with m/cs in general so thought I'd ask.

One other thing... it's burning out bulbs. Regulator/Rectifier?

Blocked fuel tank vent???????

Freshly restored? what was the inside of the tank like? Sounds like its running out of fule. Filter in tank pluged, bunch of stuff hung up in petcock, Inline filter, mabey float, needle, and seat sticking or improperly adjusted.
As far as the bulbs go im not sure just diagnosed a bad regulater on the BA and I was having trouble with brake and tail light bulbs earlier this summer There is good info on how to test in that thread.
http://www.bonnevilleamerica.com/forums/...0&fpart=all

Try riding it again. If it dies, open the gas cap. Whoosh?
Or.
I had a '75 one, there was a fuel strainer on the fuel tap.
A little bowl with a screen. If that looks like a muddy dime...

I tried cracking the gas cap but it died with it open. It must be blocked fuel so I'll have to dig a little deeper and find out where there's a filter. There's nothing past the tank so there must be one on the other side of the petcock.

I think those have a screen in the carb end of the fuel line like the secret filter on the Triumph twins, this could be the problem. Also, trace the fuel line end to end, it's easy to get a kink in the line that is hard to see.
Also, check the running voltage at the hot side of the coil. Many Japanese bikes of that vintage have a shunt regulator that can't keep the alternator under control if the battery is weak and not pulling its share of current. This happened on the OL's training wheels bike, the extra voltage overheated the coils and killed the spark.