I don't know why honda engineers have been using this design for so long, you figure somebody would have mentioned that they have a high failure rate.  It is my contention that although these tensioners are automatic and self adjusting they simply extend to thier full extent anyway.  So i recently bought another one of these for $50 odd dollars and it failed in 3 months.  So here is a quick story about how to fix it nearly permanently.

Take the tensioner apart and you'll see these parts although i lost the cylidrical part and it won't be needed for the fix anyway.  If you haven't seen the inside of one of these yet, that spiral steel tape is the actual spring mechanism, and it is what always fails in these things (i speak from the experience of having them break on two xr400, 1 crf450x and now twice on my 2003 crf450).  Anyway, your only gonna need from the tensioner: 1) the plunger looking two-peice, top part, 2) the snap-ring lock, and 3) the tensioner body.

http://i77.photobuck...ne/100_0227.jpg

The idea for this fix is simply to put some kind of spacer inside the body of the tensioner such that the top plunger part will be at its full extension.  At this point i won't bore you with the details but i took a bunch of measurements with my dial micrometer.  After triple checking and all i came up with a length of 0.865 inches .  The outside diameter of the would be spacer is also important and should be about 0.495 inches (1/2).  So now it was a quick search to find something that was approximately this size.

My first spacer was simply an 11/32 craftsman 1/4inch socket which is 1/2 inch diameter but just a hair too long.  Simply using a hand file i could quickly get the proper length in about 5 min.  Later i went to the hardware store to see what they had and found a coupler nut which was 7/8 inch long, which turns out to be only 0.01 inch too long, so that was easy to trim down with the hand file.  Putting it all back together and presto, a functional tensioner for a quiet motor.

http://i77.photobuck...ne/100_0228.jpg

Anyway, this works out just great on my bike, sounds good and no rattle or slappy noises.  I know some of you will look down on this fix, but this will save your ride and possibly your bike some day.  I think everyone with one of these tensioners should at least make this little part and keep it in your fanny pack or tool box.  That way, when you are on a long ride and the stock-honda-bad- design-tensioner breaks in the middle of nowhere, you can drop this little doo-dad in trailside and keep riding.  Also, with those mechanical tensioners, how do you know you didn't put too much tension on the cam chain?

http://i77.photobuck...ne/100_0229.jpg

Edited by mattydavis, 28 April 2012 - 01:17 PM.

It is a good idea but at full extension it may be too tight? Most people here just get the manual tensioner lifter that TT sells. It is a really good one, very well machined and cost effective. You can also drill out the auto lifter like yours and tap in some all thread so tht it works just like the one in this link.

http://shop.thumpert...r-p6766344.html

How do you set those to right tension n how often u gotta check em?

Dasquriel, on 28 April 2012 - 05:59 PM, said:

The manual one that I linked?

Finger tighten the adjuster bolt while turning the crank shaft by hand. At certain points during the engines rotation, you will feel the adjuster bolt tighten taking up slack in the chain. DO NOT force the adjuster bolt. Just let a steady finger tightening tension take up the slack as you rotate the crank. Once the slack has been completely taken up, back off the adjuster bolt 1/4 turn. Check it using the method I just described as often as you feel it is needed.

Edited by mrmoto35, 28 April 2012 - 06:10 PM.

The problem with locking the OEM part at full extension is that the chain is probably too tight and you're going to prematurely wear out the chain guides and possibly the left cam bearing too. Which will make you think the valve lash is going away on the left intake, when it may not be...

You can make a manual tensioner out of the OEM part too. If you find yourself some M6x1.0 threaded rod you can make a manual adjustment ram. I did this and it seems to work fine, although I run the TT part now.