The engine is not broken in yet. The grinding that you are feeling is known as "pinch" it is a tight fit between the piston and sleeve at the top of the travel, not the bottom. The piston kind of forges itself to the correct fit during break in and the first gallon of fuel.
You will have the best results if you heat the engine with a heat gun or hair dryer before attempting to start it (helps all of the metal parts to expand correctly). If it has been run before the needles should be in the ball park.
Run the engine for 3-4 minutes at a time EASY, no full throttle. Allow the engine to cool completely between runs and always turn the flywheel so that the piston is at the bottom of the stroke immediately after running. Leaving the piston up in the streoke will prematurely expand your sleeve. The temperatures need to be in the 200F* range to seat the parts.
"I have no idea what you're talking about, so here's a bunny with a pancake on it's head."
In mind and body, we're all heading towards old age. It is slower to go by bike.
Last edited by Davidka; 10-27-2005 at 05:46 AM.