Modern Vespa

Hey guys I was wondering if you could help me out. I have a px 125 that won't start. I cleaned the carb out. Put in a new spark plug. I have spark when I try to kick start. I tried putting a little bit of fuel in the engine and tried kickstarting it and won't start. It does seem to back fire a little when I try to kickstart it. What could it be ???

if it has spark and it backfires occasionally I'd be looking t the woodruff key on the flywheel. just an idea.

I would start by looking at the woodruff key. See if it's still there or in place.
Next, check the stator to see if it is properly aligned to the motor. Check the points, gap, and condenser. Change if needed.

Do a search on "backfire points" in the "Not so Modern" section to get an idea of the process of fixing your stator.

Good luck!

A bit of history is required I think. What did it run like before and how long ago, have you had any work done to it, did the problem creep up or show itself straight away?

History on the PX125 is that I bought it last October. The person told me he bought it about 12-13 years ago and it just sat as long as he owned it. I Put in a new spark plug and put some fresh gas in and after kickstarting it for about 5 minutes it started running. It ran good for about a month just driving it around for a few minutes at a time and then after I let it sit for about two weeks I tried starting it up but it ran super bad until it started backfiring and shut off. Now when I try and kickstart it it won't start and just backfires. I'm waiting on tools to come in for the fly wheel so I can take it off. The exhaust isn't clogged. And I do have spark. But it just won't start. I'm thinking if it maybe it sparks at the wrong time ????

It could be one of the crank seals is leaking. I had a similar issue with backfiring when I was kicking it over a lot and not running and when it did catch it ran poorly and backfired also. However as you say if you are putting fuel directly in the cylinder (don't put too much in) and it still does not catch then you have some great advice from the other two people on the thread.

See how you go when you pull the fly wheel and let is know.

It smacks of a condensor issue..get anew one.... and also new points while you are in there
Good luck

Hey guys I just got the fly wheel off and sure enough the woodruff key was in two pieces. I just ordered them as well as new points and condensers just Incase. Thanks for all your help I'll keep you guys posted as!!!!

Hey fellas you guys were right!!! I replaced the woodruff key and started right up. Thanks for the help!!!

Nice job guys!