Topic: reassembly: rear cam chain tensioner: Hook Bottom?

[jandrea]

1976 CB550F
I'm trying to reassemble my engine (first time) after some mods.  When i lifted out the rear cam chain tensioner during breakdown, i could have sworn the bottom end of it was hooked on something deep in the crank case.  Is this true?  Or do you just drop it in and poke the adjustment bolt through it's hole in the rear of the cyl blck?

Also, is  it always this much  of a bear to get the damn cam, sprocket, and chain back in place?  It seems as i have the rear tension spring fully compressed, but still there doesn't seem to be enough chain slack to make this happen.

Thanks for any info!
Jason

[Jonesy]

I just did a 550K. Yes, there is a recess in the bottom of the crankcase to hold the tensioner. If you hold the cam chain forward and shine a penlight down the chain tunnel you will see it. I noticed it holds the tensioner back slightly, so when you put the top bolt back in it will pull back a bit on the tensioner assembly. If the tensioner is not seated in this groove at the bottom the cam chain will hit it and the crank won't turn over all the way.

Yes, there isn't much real estate to work in when putting the chain back on. First, get the crank in the proper position to establish your valve timing (TDC 1,4). Then, note the position of the cam sprocket when it's bolted back on the cam, and noting the position of the cam for cam timing (the notch on the right-side end of the camshaft). Then, wrap the cam chain over the sprocket with the front strand of the chain taught and note the position of the sprocket. What we are doing is getting the sprocket as close to the final position as possible so we won't have to fiddle with is much when we reassemble everything (a real PITA). Slip the chain off the sprocket and carefully work the camshaft into place while holding the chain and sproket with your other hand (probably your left hand as you will likely be on the right side of the bike while doing this). With the camshaft now seated in its bearing journals, the chain and the sprocket will be loose on the side. Loop the chain over the sprocket and then move the sprocket up into the shoulder on the camshaft that keeps it on center. Line up the bolt holes between the sprocket and cam and check the valve timing. If it is off, slide the sprocket off the shoulder and move the chain one tooth on the sprocket, depending on which way you need to shift the position. If it checks out OK, install the bolts finger tight and release the chain tensioner and double check the timing. If all is well, tighten the sprocket bolts and proceed with reassembly.

<edit> Also, while holding the free end of the chain in your hand, gently roll the motor over a few turns before reassembly. You could have a small bit of chain bunched up in the bottom of the crankcase. This will deny you those precious few inches of extra length required for reassembly, and may jam in the bottom of the case when you turn over the crank!

Kinda hard to explain without photos, but I hope it helps...

[jandrea]

This is really good info...and what my gut was telling me about the tensioner.  thanks for everything.

jason.

[Gordon]

I did a short write-up with pictures on how to re-install the camshaft, sprocket and cam chain a while back because of this very same issue.  Click the link and scroll down about half-way.

http://www.sohc4.us/forums/index.php?topic=369.0

[jandrea]

bummer.  i still couldn't get enough enough slack...then i lost by brain and tried forcing it on and the sprocket got wedged....and once i got it out, i had damaged and lost a small chunk of the teflon-type material on the sprocket.  And of course...as it is with me...a light bulb clicked just after the damage was done.  I had installed the front cam chain tensioner slide in front of the cam chain as opposed to where it should have been...to the rear of the chain (or inside of the chain loop).  Once i pulled the head back off, and fixed how it was situated,  put the head back on....i tested it and sure enough there was plenty of room to get the chain around the beautifully damaged sprocket.

So now  i'm in the market for a sprocket.

But this other info will come in great handy, so thanks much!

Jay

[jandrea]

my other big mistake was that i had the cam chain as the last thing that i was threading the cam through from the right...when the chain should have been the first thing i thread the cam through...and finally the sprocket.  It kept binding on the other side.  but once i threaded it through in the correct order..it was a pretty minor affair.  I thought i tried about 99 ways to do it...and then the 100th was like a light bulb going on..and sure enough, that was it.

Thanks!