Vintage Vespa Forum

Vapor Lock? '65 SS180

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CoSS180 Andy Sherman
Centennial, COLORADO (CO), USA   USA
I have a '65 SS180. A few years ago I had the electronics upgraded to the Vespatronic 12v kit. It ran perfectly after that. A few months later, however, my crank shaft was shot so I rebuilt the top and bottom ends and the clutch. When the work was completed, I took it in to a local vintage specialist here in Denver for a fine-tune.

Cold, it fires right up, and purrs like a kitten, and idles like a champ. Unfortunately, after about 15-20 minutes of riding, when I try to fire it back up, it will start back up with a bit of work, and will drive perfectly when throttled, but as soon as it idles, the engine cuts off. It'll start right back up, and will run when I keep it throttled, but will not idle. I can be riding at 30mph down the road and hit the clutch to shift, and it will immediately die, firing back up when I release the clutch and the scooter is moving in gear (with throttle). I didn't have this issue before I rebuilt the engine, so it is definitely an issue I created.

I have cleaned the jets, etc..., but it doesn't seem to help. I have been told that it may be one of the following:
  • Condenser overheating (I don't think the Vespatronic kit has one)
  • Air leak in carb (had that tested-out and it appears to be sealed perfectly)
  • Clogged Jets (doesn't seem to help when I clean them out)
  • Vapor Lock (seems to be the most likely issue)

I cleaned the vent hole in my gas cap, but that doesn't seem to help.

Any suggestions would be awesome. Let me know if there is any other relevant info I left out.

Thanks in advance,


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