Petrol in the primary chain case

[Chris Exelby]

I accidentally left the petrol tap in the on position overnight and I noticed some petrol leaking out of the bottom drive chain case close to the back wheel. I removed the primary chain tensioner bolt and petrol (mixed the the TX fluid) ran out, I drained it fully from the chain case plug.
OK so I have an issue with the float level in the carb i can fix, but can anyone explain how the petrol made its way into the primary chain case and then down the drive chain to the back wheel? Is this indicative of seals leaking at other places in the engine?
Investigation has also shown that the petrol tap is not always ''off'' when it says so.

The bike has always been unpredictable to start, sometimes after a few kicks and occasionally many many, and often with clouds of smoke lasting for some time. Thinking about this now  this was likely caused by petrol in the crankcase being sucked into the cylinder, causing it to run very rich. burning off.

Could the petrol in the crank, plus sealing issues between the crank and the outside world be the cause of my starting problems?

[hendred]

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.