I went in to KTM this morning and while I was waiting for them to open I spoke to a mate who was a KTM team mechanic and is now with Yamaha. His diagnosis over the phone was that either the ring had cracked, the head gasket failed or the RHS crank case seal had failed.
Fix is change piston and ring since they should be done around now anyway. Check the head gasket for problems. Check if ring is cracked then put it back together and take it for a ride and see how it behaves. If its still getting oil in the airbox its possible that the RHS crank case seal may have gone and this can be replaced relatively simply by taking the clutch cover off and a couple of other pieces one of which requires a rattle gun which I’ll have to buy or take the bike in to have done then replace the seal and clutch gasket. He’s also suggested that I replace the water pump seal in case that’s the cause of the water.
I’ve ordered the three seals I need from KTM newcastle for $57 but they wont have them till next week. In hindsight I should have just tried the first step then ordered them but at least I’ll have them as spares if the problem is solved!
I’ve decided I’m going to try and work from home today so once I’ve done what I need to I can duck down and get into the piston change. I’m told it should only take a couple of hours but I’ll be taking my time. With any luck I may be able to do a test run tonight and if its good I’ll take a ride tomorrow.
BTW for those interested running the bike and even getting it to temp wont necessarily create enough pressure in the crank case to push oil out the vent hose but the build up of pressure is no doubt why its stalling. I also thought that it was hard to kick when I was in the bush but thought that was because I was buggered but from what I’ve learnt I believe it was due to the pressure in the crank case.
I’ll update through the day.
