Motorcycle Repair: hard to start and oil filled spark plug, yamaha dt 125, piston ring

Question
Sir mike,

My bike is a  1994 yamaha dt 125 model. The problem is that it is hard to start and the spark plug is always filled with oil. I have visited a mechanic and he checked the piston ring.  According to him the piston ring is okey.  He replaced the oil seal. But after a while, the problem persist, it is hard to start and the spark plug is filled with oil. I observed also that the spark plug do not last long.  Sometimes when i am starting the motorcycle it is backfiring.

Sir Mike, what do you think do I need to check?  

Answer
Hi Joseph,

I recommend you buy the service manual. The manual will help with troubleshooting problems and maintaining your DT.

I would first check cylinder compression to learn the condition of the engine. Make necessary repairs to restore compression.

Fouling of the spark plug could be from lugging the engine while riding, improper starting, worn cylinder/piston rings, ignition problems, or other.

Respectfully,
Mark Shively