Detonation on RM125

[C.Hoddy]

I have a 99 RM125 that I just had the cylinder replated on, and I also added a FMF SST pipe and silencer, but I am having a problem with detonation and losing power on top end. It only Knocks when I am riding it, it wont do it when sitting on the stand and being reved up! I dont know much about jetting so i am looking for advise on what to do from here. Also the plug is dark and dry on the porcelin but oily on the threads.

 

[skhasky]

Hotter plug will help on the oily threads. As for the knocking... try race gas - Phillipd B-32 and see if it goes away. If it does, it simply means your motor requires the higher octane. BTW - it usually won't ping on the stand. The engine needs a load for this.