SF3 over-running

M

macavity99

Full member
Location
Bedfordshire, UK
Not a big problem but a nuisance. The engine wants to keep reving when I shut the throttle for a gear change. Blipping the throttle lets the revs drop. Tuning the carbs doesn't seem to help. I've heard that mixture screw adjustment will help but hasn't worked for me.

Any ideas?

Cheers

macavity99
 
macavity99 said:
Not a big problem but a nuisance. The engine wants to keep reving when I shut the throttle for a gear change. Blipping the throttle lets the revs drop. Tuning the carbs doesn't seem to help. I've heard that mixture screw adjustment will help but hasn't worked for me.
Click to expand...

Running lean at idle??

What type ignition?  Mechanical advance/retard contraption working correctly?

Lean idle mixture might be caused by extremely worn throttle slides, no manner of screw twiddling will cure that!  Throw a bundle of bucks at the carbs or swap for new/modern ones if so inclined, really makes a difference!

A sticking/worn advance/retard mechanism will keep the revs up as long as it's stuck in the "advance" position.

Just a couple of ideas.... :D

piet
 
Check the throttle slides and carb bores are clean.  Shouldn't be a problem with a steel fuel tank, but ethanol in fuel does horrible things to epoxy...which has a habit of collecting as a sticky black residue on the slides.

Cracked/leaking inlet stubs/balance pipe?
 
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