Topic: Cam chain tensioner demystified (CB550)

[mikethejeepguy]

I've searched and read and pondered, trying to figure out how this tensioner works. There is a lot of information to be found on how to adjust it, and I've tried pretty much all of them before making peace with the fact that my tensioner had bit the big one. On the other hand, there is very little, besides some micro-fiche illustrations, on what it looks like and how it operates. SO, before I installed it into my motor, I decided to take some pictures and this video to hopefully answer any questions for people trying to figure this engineering marvel.  Maybe one day it can go in the FAQs and I will feel like I have finally contributed

http://www.youtube.com/watch?v=rBGKxgH7q9o

[OldSchool_IsCool]

Well done Mike!  Thanks!

[TwoTired]

It's a good video.  Thanks for that.

It does leave out an important specific and important function though.  I'd like to add that here, if I may.

As the tensioner moves, you'll note the part that slides near the adjuster stud.  When that stud is cinched down, friction clamps that slider and prevents the shoe from changing its arched position.  This is important, as when centrifugal force from the chain is applied to the shoe the position adjustment would change if the stud did not prevent that slider from moving.

The lock nut essentially provides two modes of operation.  Hold position and take-the-slack.  Hold position is a run mode, take-the-slack is an adjustment mode.  All that is required in take-the-slack mode is that the cam and crankshaft are placed in position so that the slack side of the chain is on the adjustment shoe side.  Then the tensioner can hold that position when the lock nut is in run mode.

[mikethejeepguy]

You're welcome OldSchool! I hope to add some more close up pictures of the cam gear etc later.

Great info TT! I didn't know about the sinch down. Glad you chimed in. Reading through tons of posts, I just noticed that many people (read newbs like me) seemed bewildered by the whole cam chain adjuster deal. Hopefully this thread answers most of those questions.

M

[jimbir]

This is one great video! I can now see how this darn thing works. Thank you! It should be posted as a sticky at the top of the tech, tips and tricks, and the faq forums without a doudt.

One question, if I may. Should it be possible to rotate the tensioner screw with a screwdriver? With the lock nut loose, the screw is free to move in and out but, I can only turn it, maybe, 10⁰ or so. Maybe there's a mechanical advantage issue here. If somebody can answer that, I will know everything.

[crazypj]

One question, if I may. Should it be possible to rotate the tensioner screw with a screwdriver? With the lock nut loose, the screw is free to move in and out but, I can only turn it, maybe, 10⁰ or so. Maybe there's a mechanical advantage issue here. If somebody can answer that, I will know everything.

 You can see in the video the screw head moves a little more than quarter turn with tensioner out of motor.
When assembled tensioner cant move to full extended position ( even with worn chain/blade)
So, 10 degrees is about right.
 BTW, I posted pics (but not vid) of this a couple of years ago, the same questions, the same answers.
 I guess search doesn't work anymore?

PJ

[Simpson]

I don't have a 550 but that's a great post. 

[fastbroshi]

  Just one little tidbit I wanna throw in here in case anyone's interested, got this one from TwoTired I believe:  when adjusting the chain, don't hold the adjusting stud with your screwdriver very tight.  It needs just moderate pressure while your locking down the nut. 
 
  Sure it runs super quiet with it super tight, but not for very long.  Much longer between adjustments with moderate pressure while locking it down.  This has been my experience after replacing the blade and assembly on my 550.