400ex woes

[kidkrawler]

My buddy bought a 2000 400ex 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 four wheeler owner would do, tore the **** 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 ***!! 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!!!

[prepracing]

as for the valve clatter, hotcams are known to cause louder than normal clattering sound. If you are using the TDC mark on the flywheel clearance should be .004 clearance on exhaust and intake, although some people run 005. I have seen honda manuals and clymer manuals actually reccommend different clearances. I have mine both on .004, but thats just me. As for the power issue, if your vlave clearance is way to loose it will have no low end power. Did the rockers appear to be worn ? Also is this piped or jetted with any kind of airfilter, could also be a jetting issue. Thats just a couple things I can think of off the top of my head. Good luck

[kidkrawler]

it has k&n's and some big gun exhaust, but has anyone had the valves at tdc have that much jump in them? I mean the exhaust valves are normal but the intake just rock back and forth so we cant adjust them

[mikeboone]

Originally posted by kidkrawler
it has k&n's and some big gun exhaust, but has anyone had the valves at tdc have that much jump in them? I mean the exhaust valves are normal but the intake just rock back and forth so we cant adjust them

The valves dont get TDC; the piston does.

The lash can be set regardless as long as you have no wore out/broken parts.

[kidkrawler]

I understand TDC otherwise I would not be working on this, when the engine is at TDC the intake valves can be lifted up and down at least a quarter of an inch, making it impossible to set valve lash to .005, that is my problem

[bwamos]

May have bent rocker arms then.

With your piston at TDC, both intake and exhaust should be .004 - .005. If you can not adjust it to within that tolerance, then you have an issue outside of adjustment.

Pull off the head cover and inspect the rockers.

[400ex100]

the problems i think you have would be the shop that you took it to put the wrong valves in it (to short) or the rocer arms are bent but for the arms to be bent the valves would have been bent when you first took it apart.

[slamdak8782]

if you can pick the rocker up at any place as it is turned there is a problem there is only one point where you should bee able to do that. Any other place is just not right because there should be sprng tension on the rocker. So I would try resetting valve clearances sounds like they are way out because you should only be able to move them a little bit. just enough to feel it like any less and they wouldnt move. What might have happened because when I set mine i did this the first time, is they set it to the key they give you which is metric only the used standard feeler gauges. I messed it up on mine because on american cars they are usually set in thousanths not micrometers. And yes they are loud because they are at like 12 to 13 thousandths instead of 4 or 5 that they are supposed to be at

[400exrider707]

Just so you know the lash should be .005 intake and .006 exhaust with that hotcam too.

[Chicksdigme423]

i have a feeling it might be your rockers, the lobes on them are worn, i had the same thing with my 300ex, i had to keep adjusting the exhaust and it ended up just wearing out to the point where i HAD to get a new one and a cam, so before you keep riding it pull that valve cover and look at the rockers where they touch the cam

[dariusld]

Originally posted by Chicksdigme423
i have a feeling it might be your rockers, the lobes on them are worn, i had the same thing with my 300ex, i had to keep adjusting the exhaust and it ended up just wearing out to the point where i HAD to get a new one and a cam, so before you keep riding it pull that valve cover and look at the rockers where they touch the cam
He said a quarter of an inch. I don't think they can wear that much.