Re: Mikuni Carb

Posted by Garenne on Jan 09, 2025; 5:53pm
URL: http://silk-motorcycles.221.s1.nabble.com/Mikuni-Carb-tp5001990p5002648.html

Just another belated update on the Mikuni settings that I am now running on my Silk. The current settings are:-

Mikuni VM 34
Slide   2.5
Needle 6DH2
Needle Jet 159 Q – 2
Needle clip 2nd Groove
Main Jet 360
Pilot Jet 22.5
Float Height 24.0mm
Air Jet 2.0mm

I have now done nearly 7,000 miles since first getting it going.   I think that I am as near as I am going to get without finding someone willing to put it on a rolling road with appropriate testing gear.  I found the pilot jet was too big but going down below 20 at one point with it still improving the slow speed running I felt was a step too far.  I had visions of the jet getting easily blocked without extremely fine filters in the system.  I have had trouble with overspray inside the tank being dissolved by the petrol after having to resort to E10 fuel on one trip and causing a blockage with the current 22.5 jet.  The bike is now just about acceptable trying to keep down to the 20mph town speed limits that are now imposed in my area and quite happy at 30mph once warmed up.  Other than that it just feels right and very responsive all through the throttle range although I have not ventured more than 80mph on it, just to see how it performed.  
The only thing now left to do before the up and coming season is to find where a pesky water leak has developed in the barrel or head that is draining down into the crankcase.  Fortunately I did make some drainage holes in the crankcase earlier which have come into their own with this problem.  At least I have been able to keep riding it while trying to sort the problem with K-seal leak repair by just draining down both the radiator and engine after every excursion.  Having renewed a head-gasket already I think that it may well be yet another casting flaw.  I shall be doing a pressure test on the assembly before trying yet another head-gasket if that is what it proves to be.