If it were valves you'd hear them clanging. On the 400EX for some reason they left the decompression parts in, used on the XR400, they're found on the camshaft. If installed wrong these decompression pieces make a lot of noise too.

 

Check all your motor mounts. If they are loose it will vibrate bad on deceleration. Retorque to spec. Hope thats all it is! If not take it back to the dealer.

 

well just load it up and take down to the shop.

 

Santa,

What was the outcome?

 

Well I started with the engine bolts, all tight except for the one I twisted off! I hate it when that happends. How am I stonger then that thick bolt? Anyway, I had a couple of friends come by and have a look. They have never seen anything like it. They both could hear and feel the vibration coming from the engine. The only idea they could come up with was valve clearence. I hate to say it, but I did not properly break in my quad. I guess I was Just to damn excited and could not wait to rip it up! My engine has been noisy from day one, so it is hard to listen for the valves. I will have the valve checked by next week, I'm not qualified by a long shot. Any ideas before then please let me know. I hate to pay $100 to find out its not the valves!

Help!!!!!!

 

yup, that's the problem, improper break in.

 

i have a question that is kind of in the same category. my valves constantly need adjusting. my friend used to work at the place where i bought mine, and he did all the work on mine for me. i dont see him very often now, though. so does ne body know the valve clearance specs for the 400ex? also, does ne body know why my valves start chattering again so soon?

i ride a 2000 honda 400EX with maier purple plastic, purple renthal bars, black seat cover,motion pro twist throttle, prm full body skid plate, prm swing arm skid plate, prm front bumper, sunstar sprockets-2teeth lower gearing, 20 inch turf tamers on rear, graydon proline aluminum nerf bars. go to www.angelfire.com/stars/stuff4

 

Took my quad to the dealer today. The tech's said they never seen anything like it. They say that the 400 engine is bullet proof! The dealer is going to contact Honda to see if they have heard of this before. I'll keep everyone informed with the outcome. I'm praying my warranty will cover this!!

 

.004" Intake
.005" Exhaust

I have only had to adjust mine once so far, originally purchased it in August. It has been ridden hard.

 

Do you have a Chassis skid plate? That was what mine was. I kept hearing a vibrating noise on deceleration, I thought it was my valves, so I took the skid off and the sound went away.