vespa p150x not behaving itself

[john]

Hi wonder if anyone can help ? The scooter is hard to start, once going seems fine and runs ok although lacking speed (55 tops), the problem i have is when i leave it ticking over for any amount of time it starts to missfire wont rev clean and stalls. Check plug and its black and sooty...now it has a new plug, new rings fitted, spark is good, timing is good, carb has been removed and cleaned all dellly jets are correct to book, the mixture screw is 1.5 out ,can't think what else it could be...any ideas? thanks John

[wack 63]

A few common problems are Frame breather hole covered over
Float bowl over flowing thru the brass pipe into carb bore
Drive side oil seal (check gear oil and hand over tailpipe)
Choke sticking on
Exhaust blocked
Damage to rotary valve on casing and crank (look down open carb bore while turning flywheel)
Plug cap breaking down
Just a few to check there's probably more. 55 ish mph is about it for a 150 isn't it?

[john]

Thanks Wack63, the frame hole is clear, the choke is fine, there is no petrol smell in gearbox oil...should it stall if i cover the exhaust ? (if the seal is ok ) rotary valve is in good condition, not completely sure of exhaust but looks perfect from outside..is there any way of knowing if its blocked, it doesn't sound like its full off rust when you shake it ? The float needle valve is newish (red top) no ridge worn on taper, i have tried another cap and scooter behaved the same although i will buy a new one to be sure. The other major problem i forgot to mention is that it is very juicy...60 miles from top to reserve, now i get that when i put the 210 engine in.

Thanks again John

[timexit17]

Try changing the coil too.
P150x early have points: look at those also if it's the points model.
Sounds like it's drinking way too much, but a genuine 55 is about tops for a 150, unless you are very light?