Topic: 1973 CB500 Four - Can't Install Cam Chain - HELP!

[Bear Four]

Hi all, I am reassembling this bike and am unable to get the cam sprocket onto the cam. I've got the chain on the sprockets but can't get the sprocket to lift up onto the cam boss. It's like the chain is too short. I have the adjuster at the bottom of the cylinder block screwed all the way in clockwise. I have the bolt at the top rear of the cylinders screwed all the way in too. The tensioner is fully inserted into it;s pocket in the crankcase. The slipper is installed into its slots. 

There appears to be zero free play in the chain already. I tried the screwdriver down the back of the cam chain tunnel. That was enough to get the chain onto the sprocket, but not the sprocket onto the cam.

Two things I notice. The slotted stud of the tensioner only has about 1/8 of a turn regardless of whether the nut is tightened or not. second the top mounting bolt for the tensioner has to pull the tensioner in to the back of the cam tunnel.
You can feel spring resistance as you tighten that bolt.

My only thought is that I haven't got the tensioner fully into that bottom groove.  So do I have to take the whole thing apart again?  I used the Clymer manual. The slipper is mounted to press against the inside of the chain as per the manual. The tensioner obviously can only press against the outside rear of the chain. What's the fix?   BTW I dismantled this bike in 1979, as far as I know the bike has never been apart. 12000  miles only.

[bryanj]

Two things
(1) NEVER turn the adjuster with a screwdriver

(2) Have you got the front cushion on the wrong side of the chain?

[Bear Four]

The Cam slipper is installed pressing on the inside run of the chain, facing towards the front of the bike,   as shown in the Clymer manual.  The bottom peg fits into a slot in the crankcase and the top peg fits into a slot in the cylinder barrel. it does not move once installed.

Re the slot, I saw a guy dismantling a CB550 and he was turning the slotted stud while unscrewing the lock nut.  When the bike was dismantled I observed the turning the stud could turn about 90 degrees. Now that its installed you can hardly move it at all, indicating to me that all the slack has been taken out of the tensioner.

[bryanj]

Using a screwdriver in that slot forces the gear to try and move the tensioner which in most cases forces the teeth out of mesh and springs the sides of the pressed steel tensioner meaning the rack and gear never mesh properly again totally wrecking a very expensive part. I have seen this too many times to ignore and honestly wish Honda had NEVER put the slot in the end.
Only safe way to allow all the slack in chain is with nut loost put a finger in the camchain tunnel and push the rubber slipper towards the rear and hold it whils locking up the nut.

If you really have no play in the chain check it is on the crank sprocket properly, it can knot up in the lower case.

[DaveBarbier]

How close is the sprocket to going on the cam? Both my 550 and 650 didn’t have enough slack to just lift the sprocket on the cam with my fingers. For both I gently pried the sprocket on with a large flat head screw driver.

Is this a new chain or the original?

I think you May have done this but I do what was said above and push the rubber bow of the tensioner flat against the back of the motor with the locknut loose, then tighten the locknut. That gives a lot of room.

Take a few pictures of the whole thing. Your cylinders sitting totally flat on the case and head sitting flat on the cylinders? All torqued up?

You can spin the motor and the chain and sprocket moves along with it nicely, right?

[Gordon]

Take a look at this post from the Engine FAQ:

http://forums.sohc4.net/index.php/topic,369.msg57914.html#msg57914

[Bear Four]

Hi Gordon.  I am in cam-chain-3  position. Can;t get the sprocket with the chain to come up enough to get onto the cam.   On my bike the top of the tensioner is about 1/8 inch above the top of the cylinder head. In your photo is seems that the top of the tensioner is actually below the surface of the cylinder head.  Do you have the retaining bolt installed at this point?  It maybe that the tensioner on my bike is not all the way into it's "pocket" in the crankcase.
Do I have to pull the head to fix this?  Many thanks for the link!!   

[Bear Four]

Thanks Bryan, Dave and Gordon!  The  Tensioner was not quite in the pocket. I removed the head, re-positioned it carefully using a flashlight. This time it felt right and the top of the tensioner sits about 1/8 of an inch below the top surface of the cylinder head, just as in Gordon's photo.  Luckily no damage was done to the tensioner. The cam install went slowly but smoothly. Do you Loctite those knock bolts?

 A great relief to get past this, thanks all!

[DaveBarbier]

I blue loctite them after cleaning the threads out with brake clean.