208 polini problem

Schaltroller / Classic Motoscooters Vespa Largeframe
1

Engine:
208 polini , race crank , rotary valve , 28\30 pwk carburetor , dominator pipe, fully retarded ignition , B7ES plugg.

Problem:
Runs great when cold , and starts easy, but when it geats worm it starts bogging and choking and won’t rev at all, but runs ok at idle.
Have replaced all electrics, the hole fuel system, tryed with the original carburetor, new polini 208 set , new head with incrised piston clarence, BUT IT’S JUST AS BEFORE.
Nothing seams to help…
The flywheel is scared on the sealing surface to the crank , and both the crank and flywheel woodruf key slots are a bit worn due to breaking a couple of woodruf keys earlier, and i think maybe the flywheel is rubbing the pick up, wood that cause this kind of problem? Shoud i use a different plug?
Any advise at all would help, because a am running out of things to check…

Johan Erdal
Rivals Scooter Club

2

Curare will tell you better but 146 seem s big to me.

3

carb set up is : pilot 136 , nedlle JJH on clip number to from bottom, 146 main… Sounds ok?
Drove it a few miles today, and all was fine again, took the flywheel on and of a couple of times before that though, so the fault has to be the rubbing…

4

hello,

B7 too hot, get a B9 if NGK 27if you get a Denso or 3grade if Bosh, but this won’t solve the problem you have, it will just avoid to have another one in the future.

Please give me your carb set up.

5

i know , but it runs ok full trottle with this don’t sound like it is to big…

6

I think most likely is ignition. If it is missing this might give the apperance of a rich mixture and explain the bogging. If the flywheel is rubbing the pick up thats the first thing you should sort. I run a B9ES in mine