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