Cam Chain Tensioner Replacement DR650

Discussion in 'The Garage' started by samalama, Oct 13, 2018.

  1. samalama

    samalama Where we going? Supporter

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    Hey! I made a little video of replacing my Cam Chain Tensioner Gasket today. Let em know what you think, and if you like it, share it!
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  2. Jenn

    Jenn praise seitan! Supporter

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    What about the whole thing about TDC?

    Did you do that? Or does it not matter for changing this gasket?

    Also, I really like your windchimes and the fact that you did this whole thing one handed.
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  3. markk53

    markk53 jack of all trades...

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    It's a good idea to be at TDC compression just to be sure. If the cam lobes are up against the valves it is possible, when the tensioner is removed, that the spring pressure could cause the cam drive to move, possibly going out of time. The chain may be loose enough on the crank sprocket to move relative to the sprocket and bingo - your cam timing is off and possibly could hit valves on the piston. I have heard of this happening a few times. My installation instruction for the tensioners I sell, has the instruction to get the engine up against compression (TDC compression) for that reason.

    Doesn't happen with multi-cylinder bikes, the drag on the cam drive and multiple valves engaged seems to hold everything in place when changing tensioners.

    By the way that is not a manual tensioner, it is the factory automatic tensioner that uses a ratchet set up. Manual tensioners have an actual screw adjuster to take up the slack in the cam drive, that you lock down in place with a lock nut against the body.

    FWIW Some auto tensioners fail eventually. They make a rattling noise when gone bad. The noise is when the plunger is pushed back in and snaps back out along with the chain noise.

    The problem is progressive and takes a fair amount of time between when the noise is noticed and actual damage may occur, no catastrophic failure (with the exception of the Honda VTR1000 front cylinder, bad news there).

    Should you run out and stick a manual tensioner in your bike? Not really. I tell people if there is no cam drive rattle leave it alone. Don't fix what ain't broke. If there is the rattle you should either replace with an OEM or put in an actual manual tensioner. I make the latter, kind of fell into it when I needed them for my bikes and no one listed any.

    Having Kawasakis that seemed to be notorious for tensioner failure, at this point all three have manual tensioners. My KLX650 had two tensioners go bad in less than 15,000 miles, then I went to a manual tensioner after rebuilding the top end. Only adjusted it four times in 30,000 miles. Not much of a problem. I checked valves more often.
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  4. mr_ed

    mr_ed Toolbag

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    I know this thread is going on 3 months old, hope I'm not zombie-ing it.

    Quick question re cam chain tensioner failing...what exactly are the symptoms? Does it make a non-stop rattle or noise in time with the engine (like out-of-adjustment valves)? Or does it come and go?

    My '06 with 9k miles is making a noise/vibe that I can feel through my pegs as well as hear, but it only seems noticeable while moving. Only while cruising though...I don't notice it during hard acceleration or hard deceleration, nor at idle. Only when there is a mild load on the engine. Doesn't seem to care whether the engine is hot or cold.

    My valves are dead-nuts in spec, and my final drive chain and sprockets are only maybe 1500 miles old (also, noise didn't change I swapped the new stuff in).

    Any other things I should be looking at considering the nature of this noise? If I pull the CCT to have a gander at it, how best to tell if it's bad or not?
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  5. Motomantra

    Motomantra Registered Lurker

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    Do something quick & easy first.
    First I'd pull a S/plug, put a wrench on the crank & gently move it back & forth. No need to actually rotate, just a little back & forth. If your chain is loose you should be able to feel some free play in the crank.
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  6. mr_ed

    mr_ed Toolbag

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    Good thinking! I'll do that next time I'm out in the garage.
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  7. markk53

    markk53 jack of all trades...

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    You need to look at the back side of the tensioner rack, it will be polished off from sliding in and out, the teeth of the rack may show a wear pattern on them, but the teeth will look fine.

    The usual symptom is rattling from the cam drive area. My KLX650 rattled at idle and up, my 250 did it at higher rpm. The way to isolate where the noise comes from is to use a mechanic's stethoscope or a long handle screwdriver. Put the tip various places on the engine while it is rattling, if the noise is loudest in the cam drive and around the tensioner area the tensioner is failing to work.


    This may or may not work. It is a problem that the ratchet is not locking in, the teeth have worn round, kind of like how shifter dogs go bad, but on a very small level. The forces of turning the engine back and forth will likely not have enough force to cause the tensioner to move like it would when actually running. My 250 was skipping four or five teeth back when it pushed back. Can't do that by hand. Realize there is a spring in there that pushes the ratchet pawl out, not a strong spring, but it may disguise what you are looking for with the hand crank method. The tensioner is still holding in place to an extent, just not well enough to work properly when the engine is running.

    FWIW I know a fair amount about this topic because of both my own experience with three personal bikes and a few others' bikes, but also because it got me into making tensioners and communications with a few hundred riders on a personal level. A few actually sent me their failed tensioners and I saw the same thing with theirs as I did with mine. I also have a fair idea of the mechanics of it, doing a fair amount of my own work on my bikes (when I had the time), consulting with a couple mechanics who did some flat track and drag racing, and with a mechanical engineering technology degree (the one where you get your hands dirty). A fair resume.

    I don't believe in selling someone something they don't need yet, so I tell how to see wear and also how to detect it. I point out the methods to find the noise source. My Zephyr 550 had a buzzing rattle from the tensioner, but after replacement there was still a rattle. Knowing the bike has a primary chain I started the bike, snicked it in gear, held the rear brake, and as I eased out the clutch, the primary chain would load and the rattle disappears. Primary rattle is no problem, cam drive was. So I say "no noise, no problem, don't fix what ain't broke".
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  8. Motomantra

    Motomantra Registered Lurker

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    So it's possible to have this problem with only 9k miles?
    Thanks markk53
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  9. markk53

    markk53 jack of all trades...

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    I had two tensioners fail in my KLX. The first at 5000 miles, the second around 12,000 miles so yes it can. Most KLX tensioners that fail usually do so under 15,000 miles and some at under 10,000 miles.
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  10. mr_ed

    mr_ed Toolbag

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    Thanks for all the info Markk! I copied and pasted this into a google doc to have on hand when I get a chance to dig into this.
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  11. markk53

    markk53 jack of all trades...

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    The stethoscopes can be had for under $10. I have a Zephyr 550, checked the valves at one time, two were out to the high side by .001". Mechanic/friends/former co-workers and generally reliable and knowledgeable good guys, when I asked said it wasn't worth tearing everything apart to shim for that small a difference to the high side. The reason for the story - with the stethoscope I can pick out the valves that are loose by where the sound is loudest. Same with the tensioner if it is bad. Besides, I can drape it around my neck and look kinda important... :imaposer:-):jack
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  12. samalama

    samalama Where we going? Supporter

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    Good stuff guys!
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