Only runs well with too much air...

First, this is a 1980 puch newport (very similar to maxi)

Well, I have kindof a weird problem...

I cleaned the carb on my bike, ever since then it only runs good if the airbox is popped partly open on one corner (getting more air)

It also idles really fast, and will overheat when idiling for more than 3-4 minutes (once its been running awhile)...

I think i may have broken the gasket on the top of the carb when I put it back together, would that cause this?

I do seem to be getting more power now than I was before... but like I said, it overheats, I have to kill the engine at every light and restart it when it turns green, not really safe...

Or did I possibly set the needle wrong?

I know one of you gurus has the answer!!!


Re: Only runs well with too much air...

Keith Wallace /

There are some possibilities...

Check to see if the throttle cable is tightened too much, and that it ooperates the choke properly. (most likely I think)

Make sure all your screws are snug, no air leaks around the airbox/intake/cylinder.

The gasket probably wouldn't cause what you are describing, but replacing it is a cheap and easy way to eliminate it from the problem.

You getting more power now is probably a result of you running lean, too much air from opening your airbox. (which is causing the overheating, I'd close the airbox to prevent damage to the engine).

What do you mean when you say overheat? Is it seizing up? If so, DON'T DRIVE IT IN THAT CONDITION! you are doing permanent damage to your engine.

Did you do anything else when you cleaned the carb?

Re: Only runs well with too much air...

Randall F /

I also had to fabricate a piece for my exhaust, if that isnt working right would that cause this issue?

I dont think it is siezing up, more feels like it just stars missing like crazy...

The service manual doesnt tell me much about the throttle cable, can you tell me how to properly adjust it?

Thanks in advance,


Re: Only runs well with too much air...

Where and what type of fabrication did you do to the exhaust?

this may be causing your overheating.

the airbox issue, it my need more air because of the exhaust issue,

you say your idling high?

there's a few factors that may cause this.

try to list everything that you worked on since performance change and what size intake,carb and pipe type you have.

Re: Only runs well with too much air...

Keith Wallace /

look into your carb body from the opposite end of your air cleaner (intake side), and you will be able to see the choke plate and the barrel that moves with the throttle cable. Push down the choke lever, and see if it sinks down all the way. Then open up the throttle all the way, the choke plate should raise all the way up. Then twist the throttle cable and watch the barrel rise. There should just be a tiny sliver open with the throttle at rest, and it should rise all the way up at open throttle. You can adjust it both at the throttle control, and where the cable enters the carb.

p.s.- do all this with the engine off ;)

You can also spray carb cleaner (small amount, it'll dry up the oil) around your head and exhaust bolts with the engine running- if the rpms of the engine change, you have and air leak there. Check your gaskets and bolts.

Re: Only runs well with too much air...

Randall F /

The end piece went missing so I had to make a 1/2 inch copper tube 4 inches long, drilled holes in the ends and put it in the baffle with a washer on the end of it then the nut to hold it all in...

Will check the carb tomorrow, thanks so far guys

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