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skipping timing chain

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I replaced the piston, rings and rebored the cylinder. It ran good for about 500 miles and then the valve train seemed noisier than the other xr650l in our group, I adjusted the valves but turned the engine clockwise during the adustment. The chain must have skipped a few more teeth then because the starter had a hard time turing th eengine over. I remove the cover and re-timed the chain and the valve train was nice and quiet, I drove it for about 200 more miles with no issues but I tried to start it and would crank over like normal until it got hard to turn over again enough that it wouldn't start.

I will take the cover off again and reset the chain.

Has anyone ever encountered this and is there a way to adjust the chain tightener?

Thanks

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is it an l or r how many miles on the motor do you prime the oil system before you ride has it ever been starved of oil shouldnt have skipped teeth unless very worn or piss poor maint. if it skipps teeth i would find out why first

Edited by bronnco79
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If the timing chain is skipping, you need to replace it RIGHT NOW. You can't just reset it; it will skip again very soon. You're way beyond the wear limit. Also check the condition of the guides and timing sprockets.

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Replace the timing chain AND the tensioner ASAP. If the engine had many miles on it when you did the piston/rings/rehone, the timing chain and tensioner should have also been replaced. I've lost count of how many people that neglected to do the timing chain when doing a rebuild, only to have to tear into it again with 1000 miles because the chain came off and toasted all the work they just did.

:busted:

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It's an L and the reason that I had to put a piston is that the air filter let some dust in and it would burn oil, it only has 4000 miles, it's weird that it would skip on start up and not while riding,

Thanks

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1.) I adjusted the valves but turned the engine clockwise during the adustment.

2.) The chain must have skipped a few more teeth then because the starter had a hard time turing th eengine over. I remove the cover and re-timed the chain and the valve train was nice and quiet

1.) You cannot adjust the valves properly if you turn the engine clockwise like that. It must be spun in the direction of operation, which is counterclockwise. The automatic decompressor will try to open the right exhaust valve if you don't.

2.) The chain actually moved in relation to the sprocket? What happened exactly?

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I was just turning the engine to check why it was noisy but in turning it clockwise it made a weird noise and would lock up so that's when I removed the valve cover and found that the chain had skipped 4 or 5 teeth so I couldn't verify that my original installation was bad or that it had skipped during operation. I'm just wondering if it somehow turned backwards a bit when I last tried to start it and that may have caused the tensionner to not work?

Thanks

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If the thing is jumping Cam chains you need to replace at the minimum the chain and the Tensioner.., If it was me I'd replace both Cam chain guides, the chain, the Tensioner itself, plus tensioner spring and maybe both top and bottom sprockets depending on the look of the wear on them,,Anything other than that is asking for a destroyed engine,,Do it once ,,do it properly ..

Turning the engine in the wrong direction when doing timing should not affect the tensioner mechanism at all..,Forget the idea..

One of the Cam chain guides breaking a retaining tab off itself is another thing that can cause the jumping,,Engine needs to be removed or disassembled down to the piston/barrel level to check

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Is there a way to check if the decompressor works, I looked in the manual and there is no mention of a decompressor mine is an 07?

Thanks

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It happened to mine too. Chain was shot. You don't need a new tensioner unless the pin can spin the wrong way in it. If anything, just replace the spring.

Here is a tensioner video.

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Did you use a manual when installing the Tensioner,,There's a few Youtube guides around on how to do it on the cheap with the zip tie..Someone will no doubt post a link Your Camchain and related bits are the problem,,The 650L has an auto decompression mechanism on the Cam itself and should also have the manually operated lever on the handlebars to activate the lever that's on the right hand top of the head cover,..The auto Cam stuffs non adjustable,,the other is via a cable..It's not or should not be the issue on the bike if you are jumping Cam chains..

There we go,,the video appears.

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In my experience it's always been the tensioner. I've had worn chains and sprockets, but I am fairly certain that it has always been the tensioner that failed. The internal one way clutch mechanism has some plastic parts. If you get the engine too hot the plastic fails and the one way clutch is no more.

I've had two fail in this manner. That last one was a bit over a year ago. I was on a long weekend and I wanted to ride! I had the valve cover off and I it was pretty clear as the chain had slipped four teeth. I removed and inspected the tensioner and found the failed plastic. After an hour of cleaning the one way clutch started working again so I reassembled and rode the rest of the weekend of what was truly epic riding.

I just replaced the tensioner and I've been good for the last year.

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Is there a way to check if the decompressor works, I looked in the manual and there is no mention of a decompressor mine is an 07?

Thanks

Your skipping timing chain is not related to the decompressor mechanism. The two are separate systems.

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How does the decompressor work on a 07 I can't find any cable, I have not yet checked if it skipped this time just that the starter has a hard time turning it over os maybe ir there is a decompressor it's not working properly.

Thanks

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Pierre,,my 08 XR650L does not have a manual decompression lever..Yours wont have it either..It is all automatic and works off of the cam..I think Horri is thinking of a different model..My XR400 has the manual lever..Look in your repair manual.:busted:

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How does the decompressor work on a 07 I can't find any cable, I have not yet checked if it skipped this time just that the starter has a hard time turning it over os maybe ir there is a decompressor it's not working properly.

Thanks

There's not a single model year of the XR650L that uses a manual decompressor. Unless your bike has an aftermarket cam installed, with no auto decomp on it, don't even concern yourself with the decomp.

It's either the guides, and/or the tensioner/cam chain that are causing it to jump the timing.

:busted:

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How does the decompressor work anyhow, just incase the chain hasn't skipped and for futur reference.

Thanks

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