400 EX Valve Help?

[01CandyBlue]

I have searched the web for a 400ex site and can not locate one so if you can help with a 400ex issue, please read on, My buddy bought a 2000 from a cousin and brought it to utah from arizona, it was obvious there was a performance problem (wouldnt pull hills, no low end) so we did what any banshee owner would do, tore the shit down, what we found is the valves were leaking badly but the piston and the cylinder walls looked great (supposedly fresh with a big bore kit?). He took the head to the local shop and they redid the seats, replaced the valves and the springs and bought a hot cam. Now, I didnt really help assemble the bike but it now starts and runs and has terrible rocker clatter, when you pull the inspection ports on the tops of the valve cover, the exhaust valve rocker arms are always tight with the top of the valve, or within the few thousandths of clearance the clymers inidcates it should have so they are normal, however the intake rockers can be picked up and down about 3/16 of an inch until the lobes come around and open the valve, so the clatter is the arms flailing about in the engine, also due to this we can not see anyway to accurately set the valve lash because the rockers are only tight when the valve is open, the clymer states to rotate the engine to top dead center and try wiggling the rockers up and down, if they barely move, all the valves are shut and the lash may be set, if 2 move and two are tight, TDC has not been achieved, well we can rotate the engine and count the firing sequence, and when TDC IS achieved, the exhaust valves are good to be set but the intakes can be picked up and down that 3/16 that was mentioned earlier, as a note the decompressor thingy has been removed due to the aftermarket cam, and the bike still runs like ass!! Any opinions would be greatly appreciated, we havent torn it back down but i will to check assembly, but when it was assembled the two that did it are very competent and had a book so we have no idea what to be checking

thanks for any opinions!!!

[racer]

so youre adjustment in the intake valve is off? thats a common thing really. and are you positive that TDC is achieved? just counting cycles wont do. you need to look into the manual for an exact methoed to tell you. i know on a warrior their is a drain type plug on the case that when removed shows a hole. and in this hole you will see an arrow denoting TDC. the arrow is stamped into the flywheel. look for something like that. or use a long pick and go through the spark plug hole. stick the pick in and let it ride up/down on the piston crown until you find TDC. thas an easy certain method.

[initall]

the best 400EX site is ATVriders.com.. They can help, i will look in my book tonight.

[sheefreak]

Make sure when your crank is lined up tdc, your cam sprocket is also at the tdc position. Don't forget the cam rotates once for evey two turns of the crank. It's a 4poke!

[thegroup]

here's some advice, buy ins. for the quad, burn it to the ground, collect the ins. $$$ and buy a 2-stroke!

[MonkeyBoy]

Sounds like a simple valve adjustment issue. You have the TDC procedure correct.

 

IIRC some cams on the 400EX require hard facing the rockers, so the cam does not wear the rocker arm down. You may want to check into that.

[KGL]

go to exriders.com Its like the hq for Honda's , check out the forums I believe they show the whole procedure there.

[2twin350s]

pull the carb off. shoot carb cleaner in the intake port with the intake valves at full rest position, see if the carb cleaner stays in the head,if not your buddy did not time the engine right and it bent the intake valves during start up, or the valves are not correct for the head, the springs may need shimmed, but usually when a 400ex jumps time the intake valves bend 1st and do not seat in the head,