starting problems... diagnose?

Hello all... I've been having some trouble with my moped, and I was hoping there might be someone here who could diagnose my problem.

First problem with my moped was a bad air filter, and a bad float. I took the carb apart, found the float was very messed up. Ordered a new float, put it in, and cleaned out the air filter. After a little bit of messing around with the idle speed and mix (the motor kept dying when I didn't have my hand on the gas) the moped ran great. For about 2 miles.

Then suddenly, -bam-. I hear this loud firing sound coming from the muffler. Sounds kind of like backfiring, but not sure. The bike has a lot of trouble starting now. If I hold the clutch and pedal very hard for a while it starts, but it won't run right (same firing sounds), and it dies after no more than a minute.

The problem isn't the exhaust (don't know if it should have been suspect.) I removed the whole thing, and my problems were not reduced.

Anyone think they know what is going on? Did I screw something up by putting the new float in? Reading fred's guide, etc. seems to indicate I might have a problem with my points, etc, but not sure. I am no doubt getting spark, since I am hearing these firings, right? Thanks a lot.


Re: starting problems... diagnose?

Chris Robertson /

Hi Justin:

Have you put a fresh spark plug in your moped? That's the first thing to try.

If you've changed your plug and the problem hasn't gone away you probably need to adjust your timing. Clean and adjust your points as described in <a href="">Fred's guide</a>.


Re: starting problems... diagnose?

Rob Hoehn /

I just recently had a problem similar to that. I diagnosed that it was something wrong with the timing. It actually turned out that it was the keyway on the flywheel that was messing up the timing. It was loud and backfired like you describe...


Re: starting problems... diagnose?

I think Fred's guide says possibly a points problem? I think that's probably the case.They may have went shut on you.They'll still fire sometimes,but it'll run terrible and pop and crack.Of course what Chris says is always the first thing to try because spark plugs are inexpensive and having a good spare plug with you won't be a bad idea.I've seen those flywheel keys go bad also.So start with the plug and go with Fred's Guide advice.BYE!

Re: starting problems... diagnose?

Pumapimp1 /

I took small gas engine shop, and most of the time, after checking all possible suspects in this problem, that little key that holds the flywheel to the crankshaft journal is severely damaged. It could be the points too, but i can't help ya there, I only dealt with mostly solid state magnito ignition systems. good luck!


Re: starting problems... diagnose?

i don't know about the backfireing but because it won't idle it might be an air leak so make sure you have all the parts in the carb.

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