Modern Vespa

Okay so, I drive my scooter to school and work 3-4 times a week. Everything has been fine aside from a few minor things here and there, but there was an issue today.

I hit a bump and my spark plug flew out. I pulled over and got a ride to work and then I revisited the scooter about 4 hours later. I bought some new plugs with me to try to replace the maimed plug.

Everything went together tight and I kicked the hell out of it and it wouldn't start. I re-tuned my carburetor and still nothing. So I ran up this apartment complex's hill and after 5 times, it bump started, I kept the revs up and got it home.

By the time I got home, the idle would keep itself alive, so I assumed everything might have worked itself out. I turned the key off, stopped the engine, and with a hot engine, kicked it and nothing. (normally it would fire straight up).

Also, in other news, the headlight stopped working again (I had this problem before and just charged the battery and everything worked out but it isn't working).

ANYTHING HELPS. PLEASE SOS.

It's always hard to diagnose online. But - are you getting spark when it doesn't want to start?

How the hell does this happen??? What does this mean? Check your plug now. Is it wet, i.e. is the bike flooded? Could be that your float / needle / something got banged out from that "bump". Given somehow your sparkplug flew out it must have been a hell of a bump! But as almogaver asks, check spark etc first. Then some more info would be handy.

you also mention that you had to keep the revs up? Was it wanting to stall the entire way home?

almogavar1969 I honestly don't know. How can I tell?

AlanMac The head is a bit stripped, but it would get loose, not pop out. It has never done this before.

I adjusted the idle set and mixture screw.

Pull the plug out, attach cap back on it, ground out electrode to engine case, turn on ignition and kick it over. If you see a spark then you know your ignition is giving spark

a) you're lucky you didn't strip all the threads on your head when your spark plug came out. my bike freaked out on me in NYC a few weeks back and I had to turn it off by unscrewing the plug and did infact strip the head threads. luckily for me, I have a spare head, an spare entire engine for that fact.

b) "rent" a voltometer and a compression tester from Pep Boys and check both. You may have a bad coil in your stator. I have a flywheel puller if needed, but do voltage tests to see what your CDI

heres a resource to read on the readings you should have and what they mean: whats the electric output on a p200 stator with polini 210

if readings are off, you may have to send out to get rewired/the coil replaced and ScooterMercato can do the work. do NOT send it to Gickspeed, he'll send your wires back all the same color.

if your plug popped out due to loose threading your compression may be balls. I agree with others - check for spark when it won't start, and check compression (preferably when warm if you CAN get it to start, but cold is better than nothing)

So there is definitely power going to the spark. The compression is also fine.

I did ride the scooter home after bump starting it for about 7-8 miles.

I'll check the reading on the stator now

the readings themselves can be specific. if its a low reading of compression, it can mean X or Y. Same goes with the voltage coming off the spark plug and stator wires. The figures are helpful.

I am going to be very honest with you, most people that knows anything about mechanics will tell you that spark plugs don't simply "fly".

I can only come with a semi logical explanation which is that your spark plug thread(the part that goes on the cylinder head) was so worn out and lose that the whole thing came out but before that happens you would already lose all power to the engine because that means that you already lost compression.

Honestly, losing the threads on the cylinder heads is a easy repairable issue. Most shop charge like $20 to re thread it. You can always buy a used head for about $35 or even a new one but like I said, a easy and cheap repair.

oh, no I get it. I just had a spare head sitting in a box of engine parts. I'll sort the old head out later.