Motor Problems (bore?)

[Jakes400ex]

I took a sissy jump with my 2001 400ex and then the engine just started knocking like with the engine rhythm and i dont know what it is. Someone told me it could be a valve problem but i dont know. I think if i bring it in they are going tell me i need it bored out and i dont know what size to go with I dont want to go all out with the 440 incase i blow it up. So just let me know!!!

[quadmx7]

if you do end up having to bore it go with a 425 kit or 416 kit. sorry i dont know what to tell u about what could be the problem. good luck.

[Jingle #11]

i say since you are new to the 400ex go with a smaller bore like a 406 i believe or sumthing equivilent to that the first bore over not a 416.

[diesel-mech]

If you have to bore it play it safe and take it to the min that cleans up the cylinder. It will be the least expenssive route and the power will most likely be similar to what you have now.

Take your front fender and tank off and check and see if any of your valve rockers are loose. My guess is your bike is fine, you just knocked something simple loose.