'79 Jawa Babbetta wont rev up

Hey all,

I just put my 'ped back together last night. cleaned the cylinder, head and piston, cleaned reasembled carb and made new gaskets for everything. The problem is it now runs almost as if it is running rich. Starts up great but goes buhh ba buhh buhh buhh..braaaaaaaap bungggg bh bhuhh (for those not in tune with moped noise writing the brap indicates strong running engine everything else is bogging noises). it will run ruff like this all day.

Even though it sounds like its running real rich inspection of the plug indicates that it may even be running a little lean. But since it wont rev up its hard to make a call based on plug colour. Anyway.. I guess the only real clue is that there is almost no trottle response. however I don't think that there is anything wrong with my cable as it appears to be pulling the needle the whole way.

I'm pretty positive this is a carb related problem (messing with the idle and air screws gave minimal change at best)However I did remove the cylinder base gasket to raise the compression (hopefully get more power) but I cant image that its related. Anyway, if anyone has any suggestions id like to hear them.



Re: '79 Jawa Babbetta wont rev up

Ron Brown /


Are you sure you sealed the cylinder to crankcase. A leak here will cause lean running.

Have you tried applying choke to get it to rev up?

Spray carb cleaner around the carb to intake andd intake to cylinder, the engine note will change if there is a leak.

Examine the main jet with a magnifier and make sure the hole is completely clean and clear.


Re: '79 Jawa Babbetta wont rev up

Hey Ron,

I used silicone case sealer for the cylinder to crankcase mount and I think that is seated fine.

The choke only caused the allready warm engine to gurgle and die (as is should).

I'm thinking that I may have reasembled my needle/clip out of whack (since the ped ran pretty good but very rich last fall) I'm going to richend up the needle setting at lunch. I think would explain why it would idle fine but not rev, I don't think it was getting enough gas to go any faster.. that would explain the hesitation and coughing as it quickly ran out of gas, reved down, got enough gas to idle again and repeat. Also might eplain why the throttle feels a little loose and inefective.

Thanks for you suggestions!


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