Topic: CB500K Cam Shaft Sprocket Won't Seat

[Dr. Frankenstein]

Working on the '72 Cb550/4 today, and have the camshaft in the head, the cam sprocket has the cam chain around it, but I can't get the cam sprocket to mount to the cam shaft! It is almost there, but I can't get it to sit on the camshaft 'shoulder' so I can bolt it down. I have played with the upper and lower tensioner bolts and tried sticking a screwdriver down the tensioner hole and pressing on the tensioner itself to try to get more slack, but it's not happening; what am I doing wrong?

[HondaMan]

You'll have to do the following steps to get enough free chain length to get it up there:
1. Loosen the upper bolt on the [rear] cam chain tensioner.
2. Loosen the middle bolt (the one that holds the position of the springs in the tensioner) and reach down inside with a long screwdriver, press the tensioner's slide back, and re-snug the nut to hold the tensioner "open", so to speak.

This will give you the slack you need to lift up the sprocket to the cam. Then you'll have to readjust the chain tension:
1. Retighten that bolt bolt of the tensioner.
2. With that cam sprocket bolted back to the cam, turn the cam until the #4 intake valve just starts to open. This will put the looseness of the chain in the back.
3. Release that tensioner nut and make sure the tensioner springs into the chain. Then re-snug that nut down.

Don't get crazy tight on the tensioner's nut: it can strip. If the tensioner doesn't immediately spring out when the nut is released, you can twiddle (that's a scientific term) the slot in that screw to help release it: sometimes the rubber tensioner strips get stuck near their top end when fully compressed into their 'ready' position.

[bryanj]

Have to ask if you are sure the front cushion is fitted right, it goes INSIDE the chain which is not intuitive

[Dr. Frankenstein]

Yeah, I got that; and managed to get the sprocket on the camshaft - I just wasn't turning the lower adjuster far enough to get the slack I needed.

BUT...! The book says to "rotate the crankshaft in a clockwise direction and align the "T" (1.4) mark of the spark advancer to the timing mark. Next position the camshaft so that the center of the cutout notch on the right end of the camshaft is aligned to the cylinder head flange surface." 

I have the advancer aligned with the "T" on the 1.4 marks, but that notch is (currently) at the 1:00 o'clock position. How do you get that notch to line up with the cylinder head flange IF - when the sprocket is secured by those two bolts - the "T"mark and the camshaft notch don't match up??   

I've tried taking the sprocket back off and rotating the camshaft within the sprocket, but that didn't do anything, it still won't line up... 

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UPDATE: I got it; I had to take the chain off the sprocket and 'inchworm' it around the sprocket to get it into the right spot - a big PITA, btw... It's now aligned with the notch AND the "T" mark on 1 and 4, and I've got the cover on, but not bolted down yet.  The book calls for six copper washers on the cover (I assume they're sealing/crush washers), but the Allen head socket screws I have in the screw kit I bought come with what looks like steel washers; it probably won't make much of a difference, would it? I've used copper washers before, on my CA77, but I'm just wondering about opinions on the subject...

[M 750K6]

Yes, fairly easy to get it on within one link of being correct. Then lift a link of the cam chain and link by link, move it round the sprocket one tooth at a time. Once I'd got it about right, I rotated the engine 360deg and double checked. I have been caught out with an untentioned chain giving a false reading. That said, my 750 was fine, but as it's easy to do, I'd suggest just giving it a full rotation, to confirm the cam is still spot on..

[HondaMan]

Don't ignore the need for sealing washers: it will make a mess without them.

[Dr. Frankenstein]

I figured as much; luckily I have a bunch of 6mm copper washers.  And I DID spin it 'round to check to make sure everything lands where it's supposed to and all is good. I'm looking forward to getting this back in the frame and finishing the build!