Topic: CB650 cam chain tensioner

[Scott S]

 I have an '82 CB650 engine in my CB500. I think the cam chain has too much noise in it.

 I adjusted the tensioner when the engine was on the stand. I've adjusted it at least three times since the engine has been in the bike and running (not WHILE the engine was running, but since it has been running).

 With the engine cold, I loosen the lock nut, rotate the engine clock wise and re-tighten lock nut. That's all my manual says.

 The CB650 has an acorn nut on it, unlike the CB500/550. What will I see if I completely remove that nut? Nothing will fall apart inside the engine, will it?
 Does the CB650 tensioner have a slot in it like the 500/550 that I can turn to make the tensioner move?
 What if I loosen the tensioner and tap on the nut with a small hammer? Think that may free up the mechanism?

 Any other suggestions to make sure my cam chain tensioner is working?

[davesee]

if you remove the acorn nut the bolt should remain in place. the other end of the bolt is a metal plate that simply locks the spring on the bow of the tensioner in place. while you rotate the engine with the tensioner unlocked, the bow of the tensioner should automatically accomodate itself to the cam chain's slack.  in my experience, you need to turn the engine over a few times to let the tensioner expand a bit. sometimes you need to give the bolt a little gentle tap to free up the spring. sometimes you need to rotate both ways to get the tensioner moving.

i have a washer fitted to the bolt as well as the acorn.

[davesee]

also, you need to keep rotating while you tighten the acorn and lock the tensioner. it's tricky.

[Scott S]

also, you need to keep rotating while you tighten the acorn and lock the tensioner. it's tricky.

 Yes, I didn't mention that, but I tightened the nut as I rotated the engine.

 I think I'll loosen the nut a good bit but leave it on the threaded rod, give it a few light taps, and maybe try as you suggested...rotate the engine more than once or go back and forth a little bit.

 This is the last piece of the puzzle for this 650 engine. If I can get the cam chain noise down, it'd be damn near perfect!

[Tews19]

Following this... You should post your video you made last on here. Maybe those who know the 650's will chime in...

[Scott S]

 Here's the latest video. It's not as noticeable in the vid as in real life. I'm confident the valves are OK. A recent valve adjustment and carb synch really quieted it up. I hear the noise in the cam chain area, i.e.; the cylinders and top end.

CB500/CB650 with proper carb synch

[scunny]

If the head has been off the motor and the tensioners bottom not sitting snugly in it's slot, you will never get the cam chain adjusted properly. This can be verified by dropping the sump and checking.

[Scott S]

 The head has not been off. I did remove the valve cover to install the engine in the frame, but not the head....at least not by me.

 I'll try the tricks while re-adjusting when I get enough time off from work.

[cb650]

If the head has been off the motor and the tensioners bottom not sitting snugly in it's slot, you will never get the cam chain adjusted properly. This can be verified by dropping the sump and checking.

I tried saying this on the 650 site but was shot down.  LOL
I wish he would just drop the pan and look.  Half the 650 videos on utube need to be checked.

[Scott S]

 Nobody shot you down. I just have no evidence that anyone's been inside the engine. I'll try the adjustment tricks and see what happens.

 It's not as simple as just dropping the pan. I'd have to get the bike up on a lift or table to be able to see anything, or use some type of mirror. I'd have to remove the exhaust to drop the pan.

 I think it's worth a shot trying another adjustment using the suggestions here and on the CB650 site.

[cb650]

34 year old part motor and its never been opened up?    Good for you you found one of the few.     It sounds Like the adjuster is wrong.   Had 3 bikes I bought sound just like this.  Even one re built by a shop.  I even did it on my first rebuild.  But as it sounded like $hit I new to find out why.   sorry  I'll go back to my box now. 
Good luck   Your build did turn out very good.

[Scott S]

 If you'll go back and look at those threads, I even posted pics and asked for clarification...IF I need to go check that adjuster.
 Take it easy, man. I'm working on it. Twelve hour shifts are rough sometimes.