Topic: Cam Chain Tensioner Spring

[rocks]

Hi guys,

I was trying to adjust the cam chain tensioner as the engine makes some noise. Somehow, I couldn't remember if it had been running this way. Anyway, this is a 1975 CB750F SuperSport with 17000 on it. The engine was never worked on exempt for some painting.
I tried two methods:
1- Use the 15° method which didn't make any difference
2- While the engine is running on idle. But with this it got worse somehow, and I could feel the plunger moving and vibrating.
While the engine idles I inserted a screw driver from the butt of the tensioner, and the noise started to go away.
I pushed as hard as I could and the noise disappeared. Man that sounded beautiful.

Now my question is how much tension the chain supposed to have?
I know it will wear out faster if there is no play, but I never heard it ran this smooth ever.
Also, I am wondering if the spring isn't doing its job.
Anyone knows the service limit for the spring? I couldn't find on the manual I got from here.

Thank you   

[ekpent]

 There is a remote chance that the shaft that goes through the tensioner and where the set bolt fits on it now may have a dimple in it from people cranking the set screw down too hard. What that does is sets the tensioner in the same spot every time as the set screw slips back in the dimple. Only way to check is remove it from the block with the 3 mounting bolts hopefully not ruining the gasket and take it apart and inspect. Good time to clean and lube and if there is an indent/dimple there try to file it flat again along that ramp.

[madmtnmotors]

Synchronizing the carbs can go a long way towards quieting the sewing machine rattles too. 

[rocks]

I took the tensioner apart and there was a mark where the bolt pushes against the plunger but no dimple, and I filed it anyway. Also, the carbs are synchronized.
Like I said, when the engine is running and I put pressure on the back of the plunger  it quiets  down, I put more pressure and it sounded great. No noise at all.

My concern is how much slack the chain should have? I don't wanna leave it that quiet then it wears out or breaks out.
 Anyone knows the service limit of the spring?

Thanks

[PeWe]

My spring has done 106.000km about 66.000mls. Same spring as the bike was delivered with.
I have a new tight heavy duty chain (max 5000km), less need of a spring pressing against a sloppy chain. The cam chain must be replaced before the spring, I suppose.

[rocks]

How do we tell when we should replace the chain? At 17000 Miles that should be fine.
I was trying to see how much slack the chain has and I figured it was at least a 1/4 inch.
I loosened the tensioner bolt and turn the engine clockwise while pushing on plunger from the back of the tensioner. I did not feel any movement on the plunger. I turned the engine backwards and the plunger came almost flush with end of the tensioner housing.

I decided to run the engine and adjust the chain until I hear just a little bit of noise. I got it to quiet, but I want it to have a little bit of slack.
 

[PeWe]

Just hope that Hondaman and other experienced CB750 mechanics will chime in.

[madmtnmotors]

I think you're creating much ado about nothing. Even when these engines are in tip top shape and running well they still have a "worn out old sewing machine" sound when running. Just the nature of the beast. It's part of their charm. 

Take it for a ride, wind er' up to 8500rpm or so, and you should no longer hear any rattles at speed. If you do, then it's time to slow down and fix something.   


Member ofreen here is closing in on 200,000 miles on his CB750F with the original cam chain and tensioner post. I am currently drag racing a CB750 with over 30,000 miles with the original cam chain and tensioner post. My CB750 street ride has over 60,000 miles on the original cam chain and tensioner post. Other members here have examples of other high mileage accomplishments, all with the original cam chain and tensioner post. 17,000 miles is barely broken in barring any serious abuse and or neglect. 

Too much tension on the chain will likely cause premature wear of the hardened rubber tensioner wheels which could ultimately lead to more serious problems.