Possibly issues with carb...

J

jaywood

New Member
Hi guys. Just recently put together an 80cc bike. I got the motor on eBay (not BGF) and all was well. I installed new mounting studs, headstuds, etc. I got it all running smoothly and decided to take it for a cruise. About a mile away from home it started running weird. I looked down and my carb was loose on the intake. I guess the clamp wasn't tight enough. Luckily I had tools with me in my backpack so I put the carb back on and tightened it and it didn't want to run right. I casually rode back home and here are my issues:

Runs fine at low speeds. When I get over 10+ mph it starts sputtering and running very bad. It won't go over a certain rpm...if I hold the throttle with the clutch pulled in it will do the same thing. If I'm riding up a hill with a constant throttle position and let go of the throttle and quickly full throttle it will rise in RPMs. I am thinking maybe it is running too lean. Any help?

Here are some pics...

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the carb does need to be shoved forward so the O-ring seals against the intake manifold when you tighten it... a squirt of sealer after it is tightened is probably a good idea.

How does it run when you have the choke on?

When cold?
After it warms up?

If running on the level, at a good clip, what happens when you put the choke on?

What's your plug look like?

:-)
rc
 
It won't run with the choke on. Cold starting is hard. The choke is basically a kill switch....that might be an issue?

It runs better cold it seems like. When it warms up the problems get worse it seems like.

Havent checked the plug...I'll do that soon ;)
 
first thing, make sure the seal between manifold and carb is good. you should also check the plug if it is running lean, that should tell if its a leak or clogged jet. then make sure the little screw-on cap on the throttle barrel slide isn't leaking either. check to make sure the jet isn't clogged by draining and removing the bowl, then unscrew the little brass jet in the center of the carb, just below the throttle slide.
 
Doh, I lied with my previous post. Must be running lean. Something must be clogged and it is not delivering enough fuel. It's easy to take the carbs apart, I think there is a video guide somewhere but even then there are not many pieces. I noticed you don't have a fuel filter. In my opinion, no engine should ever run without one. You won't get far before something clogs.
 
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I do have a filter. It's not visible though, it's in the tank. I know I need a new "in-line" one.

Thanks everyone!
 
the filters supplied in the motor kits I think should NEVER be used filter I throw them out ASAP better to opt for a good in line you can get them @ almost any good parts store pretty cheap IMO good luck keep us posted on the fix
 
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