Modern Vespa

I recently purchased a 1980 P200E. I started it, rode it around, paid the money got it home, then the problem began. I bought a carb kit, stripped, dipped, and rebuilt the carb. Tried tuning the carb, no dice. Took it to my regular repair shop that specializes in scooters and vintage motorcycles. The the receipt says cleaned and rejetted the carb (not sure what that means yet). They fixed some wiring issues and sent my stator plate out to ScooterWest to be re-magnetized. Got it back, drove it about 20 miles (back and forth to work), that evening it won't start.

I can get it to start if I close the choke, turn the petcock to C, wide open throttle, and about three kicks. It won't stay running unless I keep giving it gas. Moment I lay off the throttle it dies.

I then decided to go through the carb tuning spiel, but wanted to record where starting positions. I soon discover that the air and fuel screws were almost completely tightened. A little disturbed, I move them to 2.5 air and 1.5 fuel then go through the process of tightening and lossening. I eventually get to zero air and stop, with the scooter never starting.

I will be following up on what "rejetted" carb means, but at this point I am at something of a loss. Anyone have any suggestions? I have a compression kit, and figure I need to go there next but I'd like to know if anyone had some ideas?

air/mix screw is on the back of the carb which you can access thru the carb box. There may be a rubber plug you have to take out to do this. Run the screw clockwise until it stops. Don't murder it, light pressure is fine. Note the position and screw it out 1 1/2 turns.This is the default setting. Leave it for now. The top screw is for the idle speed. Take the carb box cover off, the air filter off and look down into the opening. Screw the idle screw in until you have 2 to 3 mm of opening on the carb slide. This should get you going. On the petcock lever - pointing to the left is off, straight up is on, to the right is reserve. Unless you have that goofy USDOT one, if so, just put it to the on position. Good Luck

That means they put a new 'jet' in that carb, it could be the same size as the original or different, and that jet is what allows fuel to flow through the carb. Or it does on my Rebel, and on most things, if you change jet size, it will also mean a few other adjustments should be made. Look at Harley's with pipes that are blue to black from the manifold heading out to the tail pipe. Sign that the carb was jetted different and no one made the other change and I think it has to do with the manafold, which I probably spelled wrong but not having it all set right can mean bursting up your valves in Rebels and Harley's

Second post on this thread really helped me get a better understanding of carb and how to adjust. I admit I had to read it a few times.

Lets talk atomizers

V.

I appreciate the carb input. I already followed the instructions here:

http://vespamaintenance.com/fuel/carbtune/


I did a compression test while the engine was cold, came up with 100 psi. Based on what I've been reading that sounds like a failure

Do I need to have the engine warmed up before testing compression?

Assuming that it failed, what next? Tear down the engine and replace all the seals?

Better compression testing is done with a warm engine, throttle wide open. 100 is on the edge, but still doable.

Throttle doesn't need to be open. Kick til gauge stops moving.

what carb do you have? newer carbs need 2,5 turns on mixture screw, my original delorto 24 needed only 1,5 turns but my new spaco is 2.5 turns, try it/

I know that your stator got re-magnatized, but are you getting a nice, strong blue spark? It can only be one of 5 things, none of which will likely need you to drop the engine and replace the seals.

(1) Squish -- unless somebody has heavily modded this thing, very unlikely to be the problem.
(2) Timing. Should be strobed after a rebuild, but as long as your stator was installed at or close to the factory mark it should fire.
(3) Compression. Should fire at 100 psi but it isn't great -- and I know you can't check a warm engine if it won't fire up in the first place. That said, have you checked the torque on the head securing nuts? Should be around 19 NM for a P200e. Considered replacing the head gasket? Isn't expensive and could be responsible for loss of compression
(4) Fuel. This might seem obvious, but have you stripped the air filter off and looked to see if mist is being sucked into the engine when you hit the kick starter? If not there is a clog somewhere, even though you cleaned it.
(5) Spark. See above. I mean, it could be that your low-magnetized flywheel was the problem instead of the stator.

I went through this last summer, it was unbelievably frustrating. Turned out to be a weak spark, and I had to replace the flywheel. But I tried everything under the sun before that and caused myself much misery. Good luck!!!!

Sorry, cylinder gasket, not head gasket. But if you have a model with the rubber band on the head (I don't remember on a p200), replace it. If you remove the head, make sure you do it in an X a quarter turn at a time so you don't warp the head.

I had a similar issue with bike not idling well when cold. I think I was not getting enough gas at idle. Solved by ensuring idle jet was clean (blew with compressed air and bit of carb cleaner). I also found the tip of the mixture screw had broken off and did not allow me to adjust carb properly.