Bogging/missing when hot

[SirHilton17]

I have a 1979 kawasaki KE 125 that runs great when the engine is cool but once it gets to full temp it seems to bog or miss or somthing.... im really not sure how to discribe what it does...
Right before the powerband kicks in it like hesitates...
It seems like a lean condition to me... like maybe crank seals.
the jetting is fairly good..
The plug is a medium shade brown color.. slightly carbony.. but not any where near fouled...
I will try a new plug today but i dont think that is what it is....

I would have posted this in the vintage form but i never get any replys in there....
This bike runs on premix, and has a newish top end (~10 hours)
Any ideas?
Other wise this winter i might split the cases and put in new crank seals and mains....Thanks

 

[RAMHEAD]

Does that bike have the carb in the side cover? Is it getting enough fuel, have you checked the flaot level? Is the air filter clean?

 

[SirHilton17]

Yup.... Carb is on the side cover... i have played with the float a bit.. just to see no reall result... it does seem like it is getting enough fuel... to me it does no feel carb related.... because it is only at a certain spot in the powerband and it runs fine every where else but in that one spot.... i hope that it is not electrical, i do not like working on electrical and im not very good at it. I think that i might play with the carb and plugs and stuff.. and if i dont have any luck i think i will split the cases and put in new crank seals..
Any other ideas?

 

[24]

Lean jetting, clean your carb your jet needle might be clogged with varnish and what ever's floating around in there.

 

[nickyd]

repack your silencer too!

 

[NO HAND]

Lean jetting, clean your carb your jet needle might be clogged with varnish and what ever's floating around in there.

Cleaning out the varnish is a very good advice, I might add to use carb cleaner to make the job easier. Sometimes varnish is so tough to remove, you need to let it soak in carb cleaner for some time, before you can scrape it off. An old toothbrush works well.

 

[SirHilton17]

Yea I have cleaned the carb... it was very clean from the day I got the bike(I took it off before even running it because I figured it would be varnished due to sitting for probably 5 years) I have cleaned it a couple more times after that....
I have set the points, put in new plug, messed around with the jetting, played around with float level, new top end..
All that helping the performance of the bike, but still after it gets fully warmed up it hesitates....
I think I have it narrowed down to leaking crank seals or some sort of electrical problem...
It’s really crazy, it runs like a champ until it gets fully warmed up.