I was riding my 400ex the other day when it started acting funny. I was going around the road when it started pulling against itself. I pulled in the clutch and the engine quit. I tried to start it and it wouldn't start. I waited about 45 minutes and tried to start it. It started fine but the top of the engine was knocking pretty bad. I drove it home and it quit knocking. I started it up about 20 minutes later and it started knocking again. It had plenty of oil and I wasn't running it hard at all. I was playing in the mud earlier that day but I dont see how that could have done anything inside of the engine. I was wanting to know what could be wrong?

 

If the noise is more of a ticking sound it is probably the valves, need adjusted. As for the akward running, it sounds like something is causing excesive resistance somewhere...

 

Sounds to me like you might have a scuffed piston or a bad wrist pin . Does it do it only when the engine is cold? What weight oil do you run?
Change the oil into a CLEAN container and check for metallic debris. Do the same with the filter.
Lets start there and you can let me know what you find.

Dave
Senior Aviation Technician
CF-18 Hornet Cell
Aerospace Engineering Test Establishment

 

I was running the regular honda oil. And the engine was hot but not overheating when it done that. The engine knocks all the time whether its hot or cold.

 

take cam out check it for excessive scratches and check valve clearances, also it might be a good idea to check ur timing