Engine fuelling woes

[ninja_fox]

Looking for some advice on fixing the engine on my 125 vespa - it's been running well but after a quick blast down the bypass it's not very well...

It starts and idles without a problem but open the throttle and the engine dies.

It has got fuel, I've checked that. And there is fuel going into the carb (remember them?). It's definitely running lean when you open the throttle, I've been through and repaired a split air intake hose to the air filter but that hasn't helped.

If I restrict the air flow into the carb then it runs much better and pulls well but I don't think that riding it around with some gaffa tape over the air intake is really a proper fix.

Any ideas?

[Green_Ninja]

drop the float bowl off the carb, check for debris, make sure you haven't got a partial blockage in the Main jet. Also you said you've fixed a leak between carb abd air filter, check between carb and engine for air leaks, is the engine piston ported, reed or disk valve?

[ninja_fox]

Thanks GN - I've worked through the pipes from the carb back to the airbox (if you can call it that) and there all ok.

Probably should have mentioned that it's a 4 stroke, which might make it a bit easier. Wasn't sure if there was a relatively simple thing that I had missed before getting the carb off. Didn't know if it might be a split diaphragm or sticky float...

[Alzo]

Possibly electrical....coil issue...not happy under load.

[ninja_fox]

I did think that but it rides relatively well if I tape off the air intake to ritchen up the mixture...

[Green_Ninja]

I did think that but it rides relatively well if I tape off the air intake to ritchen up the mixture...

is it a CV carb? if so check the slide is lifting under vacuum as it should, if it's not that would explain the weak mixture