Frustrated 2 stroke rider on cam chain.

I bought a 2000 YZ426 with a toasted motor after selling my RM250, I rebuilt the motor and have gotten it running (after ONLY 5 kicks :lol:, but now after breakin the motor in and light rides down the alley and back, (after it warms up) I hear a "rattling type noise in the stator/timing chain area, almost like the chain has slack and is hitting the stator plate. It's a new complete crank/bearings/top end/cam chain/tensioner set, and everything was reassembled beside the manual note for note. Anyone have any suggestions as to what it could be? I've tried to supply as much info as possible, i took the magneto cover off (don't have a flywheel puller yet, in transit, shop removed it last time) and there seems to be aluminum in the ran strong as hell :thumbsup: in what little time i tested it, and so badly want to have it completely tested, running worry-free by the next race weekend :awww:. Please help me... I've got alot of time in this motor already,am running out of ideas :lol: and have already missed 2 races.... >>>FEEMIN<<< I know it's impossible to diagnose by typing, but any of you 4 stroke guru's come across anything similar? ANY info, suggestions, or direction would help, and i offer any info needed for assistance.... thankz

the slapping may actually be your did chain slapping your swingarm guard.. also you need to check to make sure your cam chain tensioner is released putting tension on your cam chain ..

sure it's not just the cam chain making it's usual buzzing unlike a 2 stroke...??? :thumbsup:

These are not "quiet" engines, they make a lot of mechanical noise. That said, I don't know if your noise is normal or not. My best suggestion is go to the local track and find someone with the same bike. Compare the sounds and see if yours sounds similar, and play it from there.

It's possible that the cam chain slipper guide at the front of the engine isn't seated properly. It takes a bit of slack out of the chain and if it's not installed correctly the tensioner can't take up the extra slack.

If i remember correctly it would be difficult to miss the designated seats for the front slider, however i've seen and probably done a lot stranger things... I know it's not the DID chain on the swingarm guide cause it sped up with engine speed while sitting still. I do know of the noise you speak of cause I did have to question that when i heard What really tosses me, is that i only hear the noise after it warms up, not on initial startup. I may just buy new chain guides,necessary gaskets, and such and throw them in. Anyone know if there's a screen in the hose barb of the "oil tank" in the frame? Someone told me about this, which i didn't know and i didn't clean it in my rebuild. I hope that isn't part of my problem My flywheel puller came in today so i'll be tearing into the bike ASAP. :cry:PLEASE LET IT BE SOMETHING SIMPLE!!! :thumbsup:

i also have a 2000 426, and it makes alot of internaly noise in the top end area. i have only noticed it when it is warm, but that may be just cuz i was looking for what i thought was a leak. but yeah, they are loud inside.

Does the noise go away, or significantly diminish if you pull the clutch in and/or put the bike in gear at a standstill? If so, you're hearing the transmission rattling around at idle and low speed. Even V8s don't run at a steady speed at idle, but speed up and slow down between firing. In a thumper, this effect is very pronounced. Check this, and compare with another bike.

When setting the cam chain tensioner, be sure that the front side run of the chain is tight (pulling the cams) so that the tenioner will travel as far as it should. As a camshaft rotates past the center of the lobe (valve fully opened), the valve spring will "flip" it forward, tightening the back of the chain instead, and possibly cause improper adjustment of the chain.

Before you tear it apart, remove the tank and the valve cover and get yourself a good flashlight and look down the cam chain area. You can't see everything, but hopefully you can see the guide that you're concerned about.

Nah, working the clutch, and neutral to 1st or 2nd, doesn't change the sound, and you can hear it while riding down the street (with no helmet on :thumbsup:). However, cold it doesn't make the noise, or not as loud at least, and it changes with engine speed. The focus of the noise is more towards the magneto cover, than the top of the engine, but thinking about it I don't see how it could rub anything as the tensioner guide has a slotted bracket at the bottom to keep the chain centered..... kinda.... :lol: I guess i'll know tomorrow night. thankz for everyone's response and efforts to enlighten me. You all are the reason off road riding is alive, and tightly knit as it is today. :lol::awww::lol:

Can't wait for next week at Mt. Morris......... :lol: Rootin for #14.

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