Modern Vespa

My '79 P200e starts easy enough in the morning. Sometimes it takes a few kicks, but normally starts on first or second kick. My issue is that while idling the idle will be fine, and then all the sudden it will blip and die. When this happens, the bike is hard to start for a while like the bike is flooded.

I can feel sometimes when riding that the bike seems to either flood or miss a spark, but normally while throttle is engaged no problem, but on idle it idles fine but will blip and die.

Today 37 degrees F out, started first kick, road three miles to work, pulled up at stop light, and blip and died. This was on a hill and bump start wouldn't even start it back up.

Premium gas, and fairly new spark plug.


Thoughts?

Why not test your hypotheses?

Could be CDI failure, which can manifest with intermittent loss of spark in my experience

Although I've never noticed a "blip" before no spark sets in, so this could just be some crap transiently gumming your idle jet and causing a starvation death. I doubt flooding is killing your bike, but the converse could be true: if you have no spark, you could be flooding your bike while trying to restart. If it's a fuel thing, I'd argue it's going to be starvation

Could be something as simple as a damaged spark plug boot or loose HT wire.

When something like this happens, you need to determine if you are even getting spark, then you can start isolating the problem. I doubt it being 37 F has anything to do with it stalling out.

To test, I have pulled my spark plug out of the bike and kicked and I see spark every time.

I rebuilt my carb 6 months ago due to a broken gasket that was causing an air leak. At that time, I soaked carb, jets etc in carb cleaner and blew it out with compressed air.

I do have an inline fuel filter, and my petcock could be clogging as well. I haven't had a chance to look at those issues.

I really just wanted to see if anyone thought I was on the right track.

What's the condition of the stator and wires? Try swapping CDIs when it happens even though you get spark.

I think that may be your problem.

I could be wrong, but I don't believe you can run a fuel filter on these systems as they don't allow the float bowl to fill up fast enough.

Try to eliminate the filter and give it a go.

Stator and wires are in great condition visually Stator wires were rebuilt last year, coils are still origional CDI is a few years old, and I don't have a second unit to test with at this time.

I have been running an inline filter for 10 plus years on this bike without issue, but it could be blocked or failing.

could be wrong but you say it starts easy?

could be a faulty coil on the stator causing it to overheat once idling,you can get kits to repair,much cheaper than replacing if you can solder

If you have a clean tank, there is no need to run an inline filter. There is a small filter on top of your float bowl anyway.

Yeah, tank is clean, the filter was put in place because of an issue with cutting the fuel line a too short

Yes, kick starts first or second after opening petcock and letting fuel flow for a minute. But after the little idle/blip issue, the bike won't start for at least 5 minutes and lots of kicking and it smells of gas (flooded). Kicks and sounds like no spark, but when I pull the plug, Isee and feel spark.

I suspect you are two-feet of fuel line away from solving your problem. How does your plug look when you pull it?

Plug looks okay. not wet. Maybe Ican get a chance to put a new line in soon.

THanks

You can try opening up your fuel cap as your cap may be clogged. Maybe you are vapor locking.

This is a gravity fed system, so running a fuel filter could also lead to restricting fuel delivery under power which could lead to a heat seize.

*edit, nevermind - I see that you ARE testing when it won't start.

Yeah rode home yesterday around 40F.

Kick started 2nd kick. Road about 1 mile file, second mile did the idle problem at stop light, 3rd mile seemed file. I think Coady is on the right path with it being a fuel issue.

An engine that stops while idling is unlikely to be suffering from fuel starvation unless through carb icing. Much more likely to be flooding due to poor float needle seating. Is there any sign of fuel overflow or has somebody blocked the float chamber breather vent?

As the temperatures are low icing is also a possibility. After stopping engine heat will clear the ice within a few minutes.

Roadster, brand new float bowl and float needle in the carb after rebuild in August. No more fuel running down the back of the engine than normal on these old P's.

With old stuff like this new parts are not always of highest quality. If the float needle is all metal then it may need grinding in to improve its seating. The finest valve grinding paste can be used to do this. Does not apply to rubber tipped or nylon needles of course.
You should also try to understand how air pressure in the float chamber is kept at atmospheric and make sure the vent is not blocked. Sometimes this is a drilling which goes through to the air intake side flange of the carb and sometimes it is an external pipe which doubles as an overflow. This must not be blocked because any pressure build up in the float chamber will enrich the mixture.

Thanks. Will try to check everything in a few days after Thankgiving

I was having a similar problem. It would only happen when the bike was in neutral or clutch in.

My plug was just loose and needed to be tighten to get the full idle spark.