Re: Sticking Throttle & Float needle

Posted by hendred on Jul 05, 2020; 4:14pm
URL: http://silk-motorcycles.221.s1.nabble.com/Sticking-Throttle-Float-needle-tp5001969p5001970.html

Yes, they do that!  I believe it is cause by there being very like gap between the induction strokes on a 2 stroke twin breathing through a single carb.  This causes the slide to stick at small throttle openings when the "pull" on the slide is greatest.  My Silk did this and on one occasion got up to 10,000 rpm before switching it off!  My bike hadn't run for 20 years and the throttle bore and slide had a very light film of corrosion on them.  I polished the carb body and the slide (original alloy slide) and put a MKI concentric spring inside the existing spring.  Never stuck since.  |I believe the brass or chrome plated slides help, they are heavier too which will help with closing.  I also think drilling a hole in the top of the carb cap is a waste of time, I don't see how a vacuum can build up above the slide.  Too loose a fit in the bore and there are holes for the cable in the middle of it.  Out of interest, some time ago somebody fitted an SU carb to a Silk and reportedly it ran well.

I put the flooding of the carb down to the angle of the carb when on the side stand. The float and needle will tend to fall to one side and there is just too much friction for the float to push the needle firmly into the seat. Doesn't happen on the move because the forces acting on the float essentially go through the vertical plane (at rest) on the centre line of the bike (centrifugal and gravitational forces balancing out).  I suspect it wouldn't happen on a paddock or centre stand (there's a project for you).  

Al the joys of owning and riding a Silk.