Modern Vespa

After being stored for the winter, our scoot barely idled. Put in a new fuel filter, drained the fuel, added new gas plus some sea foam. No joy. Pulled out the carb and cleaned every jet, nook and cranny. It looked pretty good without any varnish.

Put everything back together and it idles like a charm but runs VERY VERY rough under power. Not sure I could get it up to 25 mph.

New spark plug and fine-tuned the fuel mixture (about 2 3/4 turns out) and that didn't solve the issue.

The air filter was a disaster and full of oil, so I ordered a new one. Waiting for that to come in now.

Any chance it needs pressure from the filter and won't run well without it? Also, never re-attached the drain line on the bottom of the bowl, but I can't imagine it needs that?

Any ideas are appreciated!

if you don't have the air filter in, it's gonna run ass.

if, on cleaning the carb you took it all the way down and did the needle and diaphragm, you most likely didn't seal or seat it right.

hth

Do you mean that it will run LIKE ass without the air filter?

Good to know on diaphragm. Easy to pop that off and double check the seals. That spring is a beast to get down straight when putting the cover back on.

Watching more videos last night and realized that I never pulled out the gasket and spring with the fuel mix jet... going to pull it apart today and see if that's part of the problem.

Also, make sure that you didn't lose the needle guide under the main jet. It's a small brass tube. Most of times it will fall by itself…

I definitely put that guide back in. Hopefully not upside down but it felt "right" when I installed it.

I agree with Greasy, double check the carburetor diaphragm. Remove it with its slide and try to look through it at bright light to check for any splits. Replace it if you see any. Then reinstall using some silicone grease (eg. dielectric grease) to hold the top in its groove while you install the cap.

Pulled the carb apart. Half of the fuel mix needle gasket was still there and the other half appears to be jammed deep into the carb. It will be impossible to reach unless I can figure out how to blow it out from the inside with compressed air. There's no way it would run right with that gasket shoved in there.

well, boosville on that shit. use a pick or dental tool to fish it out. you might get lucky with carb spray or the blow gun.

either way you're gonna need a new one to make that all work right. WPS or NCY has you covered, thankfully.