I was hoping somebody else would add some input to this one,
Bit of a head scratcher...I'm clutching at straws here...but is the exhaust sys the correct one for the engine and not bunged up...do you have choke on the carbs...is yes have you experimented with the at the problem RPMs to see if adding a bit of choke helps or make things worse,
If you have choke...are you sure they are fully closing....did I remember you say a while back that you had a spare set of carbs,
What method do you use to sync the carbs...it does sound like a carb prob.
Nick.
