Good Day All,

Recently finished a top end rebuild of the St'bd engine.

Heads replanned, valves replaced, new pushrods. All the normal things you would do.

Issue.
Engine starts and runs fine, after about a minute or so, it begins to fluctuate in rpm. Not what I could describe as running rough, just seems to be up and down in rpm. Unnoticeable on rpm gauge, but definitely not smooth.

Nice thing about twin engines is this is a spare parts locker a foot away.

Swapped out, throttle body, coil, whole distributor assembly. ECM.
Checked and confirmed anti siphon valve clear. Removed fuel cap, just in case. Changed all the fuel filters.

Confirmed no valve overlap.

Any thoughts??

It has the breather hoses up to spark arrestor. Do these engines have a PCV valve as well?

Has anybody had an issue with the throttle position indicator?

Sort of at a loss on this one.

Thanks in advance for your reply.

Cheers, Capt Happy