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Metal tapping after valve adjustment

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I adjusted the valves on my brother's 1999 XR400 yesterday and now hear a metal 'tapping' coming from the upper cylinder / valve area. I shut it off, let it cool, and started it again to make sure I heard it correctly. Yep, it is still there. The sound was not there before valve adjustment.

I am confident the piston was TDC when adjusting and I could feel the rocker arm slightly wiggle up and down when adjusting. Therefore, I feel the valve adjustment was done properly. The only other thing I did was 'adjust' the decompression lever (two retaining nuts) so it would have the appropriate free play on the lever.

Any suggestions on what it may be before I do any more damage?

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You could use a piece of wire in the spark plug hole to feel when the piston is at TDC.  That is plenty accurate for a valve adjustment or timing chain.  Also the lobes on the cam need to be pointing down which happens every 720 degrees of rotation.

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I used the 'T' marking in the left crankcase hole for determining TDC. Do you feel that that a wire in spark plug hole would be better? I assume I would slowly turn the crank until I felt the wire would be at the HIGHEST possible position, and make sure there is slight wiggle in the rocker arms.

To see the lobes pointing down on the cam, I would need to remove the cylinder cover. Correct? I was not planning on doing this for a valve adjustment unless it was necessary.

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You can sight TDC thru the inspection port like you did, but it can be at TDC at two different strokes. You want to be on the compression stroke for adjustment, which you were when you felt you had wiggle in all 4 sub rocker arms.

Hearing a little ticking is normal. Its when you don't hear any that you need to be concerned. Means your valves could be too tight. Too loose is better than too tight.

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Thank you for the comments. I am pretty sure I was on the compression stroke since I could wiggle the rockers a little. I will loosen them up slightly (maybe even too much as an experiment) and see if the tapping goes away.

Thank you very much for the comments! I am having an absolute blast going over this bike with a fine toothed comb. In my opinion, they don't make them like they used to!

 

13949184564_fc6840da53_m.jpg
 

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I used the 'T' marking in the left crankcase hole for determining TDC. Do you feel that that a wire in spark plug hole would be better? I assume I would slowly turn the crank until I felt the wire would be at the HIGHEST possible position, and make sure there is slight wiggle in the rocker arms.

To see the lobes pointing down on the cam, I would need to remove the cylinder cover. Correct? I was not planning on doing this for a valve adjustment unless it was necessary.

 

It's not likely but possible to have a sheared key and a rotated flywheel on the crank.  This would make the T mark useless.  The wire cannot lie. 

 

Shine a flashlight in the adjustment caps.  You should be able to determine the lobes' general positions.  They point slightly forward and back but not up.

 

Valves are adjusted cold.

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I would bet that the automatic decompression did not release and you have the right side exhaust valve backed off.

When you roll the motor around counter clockwise just past tdc then back clockwise just a bit you should here a little click as the decomp releases. If the decomp is not released you will end up with the exhaust valve to loose once it releases.

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