PX engine running problems

[Andy W]

Hi all
Hopefully someone can suggest a remedy for an engine I am working on. It's a PX80 fitted with a 135 kit, 20/20 carb standard exhaust fitted into a 65 MotoVespa. It was rebuilt Aug lats year and setup on the dyno in Oct, it used to run really well although not the fastest thing around as gear ratios limit the top speed. 2 wks ago the owner said it lacked power and could I look at it, turned out that the throttle cable had come out of it's fixing in the handlebars, replaced it in its fixing and it rode as before. yesterday owner came round on it and it would pull the top off a rice pudding now. messed around with jets, CDI, re-torqued the head, different plugs and still wouldn't pull.
It will start easily and rev no problem but just won't pull when you try to ride it.

Any ideas?

Andy

[Boothy_the_makem]

Clutch slipping maybe ???

[Polossi220]

Brakes seized had similar on a px disc front brake had jammed on

[mick1]

Rings stuck in, head blowing, main engine seal gone, blocked air filter, cdi, stator.........i'ld probably whip the the barrel off and check the rings first....

[Andy W]

Thanks for the advice guys, Brakes are ok so is clutch. I have changed the CDI, Stator and carb to no avail so now it's time to take the barrel off and have a look. Just seems funny that it ran perfectly then sat for 2 weeks and now runs like s**t. The next issue will be finding some rings for the kit, will try Sip as they advertise the kit still.

Will update when I have had barrel off! there goes another day of fixing rather than riding!!!