Valve Adjustment gone wrong....



3 replies to this topic
  • BrandonW

Posted January 30, 2003 - 01:25 PM

#1

I don't think this is a Honda specific question, so I think that I will post it over here as well.

From the Honda side of the house:

Friend of mine has a 2000 XR650R, and he went to do a valve adjust on it for the first time (under his ownership of the bike).

Here is what we know:
He is not sure that he was at TDC when he did his first "adjustment"

He thinks that he might have rotated the engine about 1/4 of a turn in the wrong direction when he was trying to find TDC.

He has gone back in a number of times, and is sure that he has has the process down correctly, but the bike is now VERY HARD to turn over; it barely runs, and when it does he hears some knocking and pinging to the extent that he he just shuts it down.

He has not loosed the cam tensioner chain, so the timing should still be the same.

Any ideas of what he might be dealing with?

Thanks,

  • Woodzi

Posted January 30, 2003 - 02:53 PM

#2

Not familiar with the 650, but I know that on the 600's you needed to turn the engine forwards only so the de-compressor wouldn't activate. If the valve is adjusted with the de-compressor activated it will be very loose (and noisy) and the de-compressor won't work (making it very hard to turn over).

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  • BEAN329

Posted January 30, 2003 - 06:36 PM

#3

this will be hard to describe so bare with me. there is a chance he has bent one or two valves. Now take a deep breath and relax here is a simple test. remove all four valve caps, look at the threads on both exhaust valve adjusters. Are they close to even or is one adjuster run in farther than the other??. do the same for the intake valves.
here is my point if you had a bent valve and you adjusted the valves again then one of the two adjusters will be run in farther than the other because a bent valve will not return to its original place in the head. the bent valve will come up short so to speak. and if you did not realize it and adjusted the valve to the proper clearence then you have made the problem a lot worse. valve clearances are measured in thousands of an inch. anywhere from 3 to 6 thousands. if you see a big difference in the adjuster height then do not try starting the engine again. the head will have to be removed and new valves installed. if you do not feel comfortable doing this test, take it to a shop that can. hope this is helpful good luck.

  • BrandonW

Posted January 31, 2003 - 06:09 AM

#4

Thanks for the response Woodzi & Bean329. Sounds as if my buddy might have jumped a few teeth with his timing chain when he turned the engine backwards. (STILL just a theory) The teeth on the sprocket the cam chain turns on are damaged for sure and the "guides" need to be replaced. Not sure about the chain itself.
Hopefully no valve/piston damage.

Bean, excellent description about how the first adjustment could have caused the problem, and the second and third adjustments only made it worse. Thanks!

Big bummer is he was just about to send his suspension off for revalving/re-springing, but not any more...

Thanks for your help TT'ers!




 
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