Runs rough below 3000 rpm

[MK1962]

My Kent runs rough between 2000-3000 and then runs great.

 

I've got Petronix dizzy and a single rebuilt 40DCOE Weber. New battery, plugs and wires. Tach is rock steady until about 2000, then goes crazy until 3000rpm.

 

Any suggestions?

[twobone]

sounds like an issue with the transition from the idle jet to the main jet.

 

How to the plugs look? Too rich?

 

Are your auxiliary venturies loose?

[The Stig]

If on Dellorto carbs it could also be the progression holes. Possibly blocked or if not, one may need to be. Had a similar issues solved with a dab or araldite in one of the holes. As two bone says though, just where it passes from idle to main.

 

Cleaning everything is a good place to start.