Modern Vespa

Hi all,

I just picked up a 79 px 125 all factory, no replaced parts except the gas line. My first vespa

At idle it is fine, but when I give it a bit of gas it eventually boggs down and stalls. At higher throttle it is fine.

The engine was seized from not running since 1985. My friend who fixes old vespa unseized the engine, cleaned the gas tank, got it running great except for the dead spot.

Idle speed is good, mix seems good - although it has t3 oil, not t2 injection oil. I cleared the blocked fuel cap thinking that was the problem, but it made no difference.

I'm stumped. Any suggestions on what to check?

You didn't mention if the carb and jets were cleaned. If they wern't cleaned, give those a good cleaning with carb spray and compressed air.

Sounds EXACTLY like the problem I had last year... slightly high idle, but super big flat spot just off of idle... if you push through that, it seemed to rev out fine.

Take the jets out and clean them with carb cleaner. Make sure to visually inspect them also. It's easy to do....

Great. Thanks for the advise. I will post back in a couple weeks with my results.

Is this a thing with 79' p125x?

Mines doing the same thing...
Tried cleaning carbs and even swapping carbs... Still doing it.

Could it be a points/condenser thing?

Mine is fine idling, can even rev it up in neutral, but as soon as it's in gear it bogs at 1/4 throttle. Once you get it through the bog, it's fine until you shift, then it bogs at 1/4 throttle again...

filter on the inlet of the carb is gunked up with oil (petrol evaporates, leaving the oil)... its under the cap where the hose connects to the carb

Classic idle mixture screw adjustment. If carb overall is well assembled and tidy, would be the first thing to try. Should smooth it right out.

Thought I had it adjusted ok...

Which way do I need to go? Rich or lean?

rich