1971 Vespa Ciao Will Not Start

I have a 1971 Vespa ciao, it had been sitting for 2-3 years I replaced the throttle cable, and put a 13.13 carb with Malossi intake on and did a 53 jet and I can pedal it and it sounds like it wants to start but will not take off, replaced spark plug as well and doing the same thing. Prior to attempting to start I did drain and clean the gas as well. Might try towing it later and see if it will kick off

Re: 1971 Vespa Ciao Will Not Start

Was it running before you worked on it?

Re: 1971 Vespa Ciao Will Not Start

It was running 2-3 years ago and the throttle cable broke, it has been sitting in the corner of my shop since, and decided to upgrade the carb on it while fixing throttle cable, I did clean the stock carb and put it back on and it’s doing the exact same thing

Re: 1971 Vespa Ciao Will Not Start

You should have got it running first, before you changed carbs. Your air/fuel ratio isn’t even close. If you have stock exhaust, you are drowning the motor. It can’t handle that much fuel. The stock 12.10 carburetor only had a 46 jet, and it’s a smaller carb and restricted air box. You put a larger throat carburetor with a bigger jet, then put high flow air filter on. Everything is off, so it can’t run. At minimum, you need to down-jet, a lot.

Re: 1971 Vespa Ciao Will Not Start

It has a proma circuit on it as well. I will order a set of 40-50 jets and try that, but like I had a said I put the stock carb back on it with stock exhaust and it’s doing the exact same thing

Re: 1971 Vespa Ciao Will Not Start

Promo circuit. Important detail, You’re probably jetted too low then. Also, check your compression. Sounds like maybe your decomp is maybe leaking causing low compression. Either way, stick with the basics. Fuel, air, spark, compression.

Re: 1971 Vespa Ciao Will Not Start

Ok I’ll give that a shot, what’s happening is I’ll be pedaling and if I open throttle all the way it sounds like it’s wanting to go but as soon as I stop pedaling it dies out

Re: 1971 Vespa Ciao Will Not Start

Check if the plug is wet or dry after you try starting it. You also might try squirting a bit of premix in the plug hole, reinstall plug, and try it. These Vespas are so picky about air/fuel ratios. It’s probably just the wrong jet, so you’ll have to experiment and plug chop to get it right. There’s also a tuning spreadsheet in the wiki that shows what others have done, to help get you close. I have an identical setup on a Bravo, and I am jetted at 69. But mine is an anomaly. It shouldn’t be jetted that high, but it runs perfect and does well over 35 mph. Nobody else who is running a stock cylinder is jetted this high.

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