Hard to start when "Hot"

[Xquzme]

Hello Fellow RC'ers, I am fighting with a 2016 KTM 390 RC. Just did all the required maintenance for the 15000 km's on out bike. Set the valves as they were all quite tight. All are set now to within the spec range and tried to be on the bottom end of the tolerance. One exhaust is in the top of the range but I couldn't get a shim that would keep it within range so I had to set it at the top end.

Did fuel filter, air filter, oil and filter and new spark plug. I did gap it to spec. Cleaned the throttle body, injector and map sensor. With proper cleaner and compressed.

The bike starts cold no issue. Runs out fine with lots of power and no hesitation. However, once the bike is up to temp it will not start. It tries but stumbles.

Anyone ever experience this. If so what did you do to resolve. I am trying not to go to the dealer if at all possible.

Thanks

Todd

 

[green_bread]

Did you transfer over the spark plug gasket? I know it sounds dumb, but I swapped spark plugs on my 2015 and forgot to swap the gasket. It would start fine when cold but would struggle to idle and/or start when warm. There was also soot being left on the ceramic of the plug.

 

[Xquzme]

We ended up doing a leak down test on the bike and the pressure was getting by the rings. I ended up having to do the top end rings and piston. It appears that the previous owner may not have winter stored the bike properly and the ring was stuck on the piston. Looks like a little carbon or rust scale got on the ring which caused the issue. You can see three small spots on the top left area of the ring (lite discolouration)