any ideas please ive recently had twin webbers and a piper cam fitted to my 1700 x flow also new valves and guides fitted the engine is now very lumpy and spitting although runnung well, would a rolling road sort it all out and what sort of cost thanks

Clean the carb jets --- idle, pump & main, check the carb "O" rings are equally tightened, Synch the carb butterflys --- by the sethoscope method. Check points gap is correct type of didtributer.

[Edited on 10/2/08 by britishtrident]

air getting in on seals from carb to manafold is a common fault also see float hights and balance the carbs
i like this you can get it on ebay for around £8 GUNSONS CARBALANCER .

when you say "recently fitted" what did the bits from from? Its possible you need a rejet etc of the carbs if all the other stuff is sorted.

Spitting back through the carbs suggests a weak mixture, but I reckon this would have to be a hands on diagnosis.

I had this a while back...was driving me nuts!
It seemed to run beautifully over 3000 revs but flame throwing/spitting/popping under 3k.

I had fitted Thackery washers......but after talking to GeoffT decided to fit 'Bobbin' style instead.....The Thackery's had disintegrated..

Been perfect since with the Bobbin style ...

HTH Fozzie

my pinto has a lumpy cam and twin 45's and it does the same. the richening up of the carbs has removed the back firing through the carbs.
but it still runs rough below 3k and then flys.

how lumpy is your cam.

ditch