Re: Petrol in the primary chain case

Posted by hendred on Jul 26, 2021; 1:41pm
URL: http://silk-motorcycles.221.s1.nabble.com/Petrol-in-the-primary-chain-case-tp5002195p5002196.html

Several of us have had this happen - see Petrol Taps -A Warning on Page 8 and Carburettor Flooding on this page.  I managed to fill the gearbox as well when about 2 gallons of petrol leaked through the engine.

The Carburettor is at quite a steep angle and the pilot jet has to be in the correct position in the carb, if not the petrol just runs through and down into the crankcase. A new needle in the carb made no difference. The inner crankshaft seals are essentially piston rings and the petrol will flow through these and fill up the primary chaincase until it finds a hole to run out, in your case at the back wheel.  

I did have problems starting my Silk when the petrol tap was passing just a small amount and I had the pilot jet in the wrong position.  I had to take out the plugs and dry them and kick it over with the plugs out to clear the excess fuel.  A new fuel tap and putting the pilot jet in the correct position cured the problem.  Black smoke indicates a rich mixture, blue/ white smoke oil.  I found semi synthetic oil smoked quite badly if there is too much supply and fully synthetic oil hardly at all.  Not tried mineral oil but from experience of another 2 stroke I would expect the Silk to smoke quite badly until warmed up.

Hope this helps and check the gearbox for petrol.