Topic: CB750 experts - HELP! I can't get my cam sprocket on the cam. I'm stumped.

[markb]

It is definitely the older style slider so the removable pin is at the bottom.

[iron_worker]

Flybox is on to it. Thread the cam through the chain and then the sprocket. If you do it the opposite way, the chain gets bound up from being flexed sideways too much.

Sometimes you can also get the sprocket fully up onto the cam shoulder with the chain only partially started on the sprocket and then use the crank to pull it around so it seats completely. Puts a bit of a lateral load on the chain so I'm not sure I fully recommend this route.

IW

[madmtnmotors]

It is definitely the older style slider so the removable pin is at the bottom.

Until this thread I was not aware of the difference between early and late cam chain sliders. You guys will teach me something yet! My engine building has been limited to late models. I revised my earlier post from "Right" and "Wrong" to "14611-300-000" and "14611-312-000" for clarity.

Early or later style, the removable pin will always be on the bottom. If the later style is installed upside down then the removable pin ends up on top...

Is this part of your "Sandcast #97 restoration"? (Which happens to be an excellent and well documented effort by the way!) 

[markb]

Thanks for your input.  There are no bad suggestions in a brain storming session.  It forced me to look closely at what I have.  Just for additional info here’s the diagram from my parts book.  You can see that if there is anything sticking up from the top of the cylinders that the guide has to be right-side-up and that the removable pin is at the bottom.  Yes, this is for the #97 project.  I figured I’d get more input with a specific thread.  I’ll take another look at it tonight and hopefully some of the other ideas will work.

[madmtnmotors]

You can see that if there is anything sticking up from the top of the cylinders that the guide has to be right-side-up and that the removable pin is at the bottom.

That would only be true for part number 14611-312-000 (early model). If you look at the later model slider (part number 14611-300-000), you will see that it will have a "short tail" (as opposed to "no tail") on the bottom and a "long tail" (as opposed to "short tail") on top. If the later model slider is installed upside down (with the removable pin on top) it would look exactly like an early style slider that was installed correctly when viewed from above. Hence my confusion when I saw the short tail up, since I knew the later models go short tail down.

I'm guessing this is a new part based on the level of attention to detail. Do you have an invoice (or order confirmation e-mail) with the part number?

[PeWe]

It is very easy when doing it right. I'm always forgetting it and sometimes struggle a lot with the "too short chain".
I have done it about 3 times this year. Soon time to change cam again.... Was it chain first and sprocket next or opposite?

I have a photo where chain first, sprocket next is obvious. Sprocket in correct place so it will fall down on cam so chain will easy will be attached. Then sprocket with chain on to the cam bolting position. Chain might need to be moved a cog or 2 on sprocket. Usually move the other direction than expected. Lift the cam chain from sprocket and move it cog by cog....
Important to turn the crank around with cam chain before and after tensioner mounted. Several revolutions and double check that the markings line up properly.
I was too eager once and had chain slack on wrong side hearing valve kissing pistons not fun. This was back in the days when I had to pull engine when lifting and timing the cam.

[markb]

Update: I got in on!  First I looked over everything down the tunnel to make sure it looked right.  Then using the bolt on the rotor I rotated the engine back and forth a few times and it went on.  I really didn't have to force it.  The only thing that worried me was there is essentially no slack on the cam chain.  When I push on the tensioner with my finger I can barely see any movement in the chain.  Just to make sure it wasn't too tight, without the screws in the sprocket, I rotated the crank one flat at a time and tried rotating the cam.  It rotated easily at every position.  I used a sharpie to put a mark on the chain and cycled it around twice.  No strange noises and no tight spots.  It is a brand new chain - I think I got it from Yamiya.  It seems like everything is OK.  Could it be that it's just that tight?  Has anyone ever had a new chain that the tensioner barely didn't move?  I have a hard time believing that it would go together at all if there was something wrong.  But I'll wait for more feedback before I proceed. 

[greenjeans]

Hopefully just to ease your mind, I've had chains of all sorts that have been incredibly tight right out of the box.  In fact my last drive chain was very stiff - almost like the rivets were all just too tight. Almost like an old bike chain that was left out in the weather to long.

Don't you just hate when you know that you've done it right, but something just seems wrong -

One day I hope to see this #97 in person.

[kmb69]

If you can look down the tunnel and the chain is centered on the center roller on the tensioner, it should be correct. Also, if you replaced that center roller on the tensioner, it could have been on the high side of manufacturing tolerance. That center roller actually spreads the chain a bit. It will loosen up some after running it at temperature and the tensioner will move in more. Is your center roller genuine Honda or aftermarket?

[markb]

Thank everyone for your suggestions.  In the end it was Charlie's suggestion that did it.

I seem to recall that the answer was (if I remember correctly) that you had to rotate the cam chain from the front of the engine.
If you rotate it from the back, it was too tight.
Charlie

Hopefully just to ease your mind, I've had chains of all sorts that have been incredibly tight right out of the box.
One day I hope to see this #97 in person.

That does make me feel better.  I'm not feeling as stupid as I thought I would.  My conclusion is that this must be one of the tight ones.
I'm looking forward to the day that it's done.  I'm hoping someday to bring it to Ohio or another of the bigger shows so you might get the chance.

If you can look down the tunnel and the chain is centered on the center roller on the tensioner, it should be correct. Also, if you replaced that center roller on the tensioner, it could have been on the high side of manufacturing tolerance. That center roller actually spreads the chain a bit. It will loosen up some after running it at temperature and the tensioner will move in more. Is your center roller genuine Honda or aftermarket?

I looked down the tunnel and everything is in line.  The center roller is Honda.

I'm still not done with the sprocket yet.  I still have to get it in time so it will have to come off (unless I'm incredibly lucky).  I least I know now that it will go on.  Thanks again for all the suggestions.

[oldhatt45]

markb,
Just Very Glad you solved the problem!!!!!!  And also glad you can now continue getting her back together and running!!!!!
Will wait patiently for progress pictures.

I think this was a good reminder for some of us, that sometimes it's the real simple stuff that we should not overlook.  LOL
(Been there done that kind of thing.  Especially for me!    )

Charlie

[754]

It's probably. Just a not pre stretched chain... Means it may need adjustment fairly soon after running.  Be curious though to see if the cylinder or head is slightly thicker.

[markb]

I agree on the adjustment.  I thought about the thickness too.  Maybe I'll check that out just for fun.  The only problem is getting an accurate measurement on the assembled engine.

[ekpent]

I mentioned that earlier also just because it seems like in the back of my head somewhere it seems Hondaman or somebody once mentioned a slight dimensional difference in cylinder height between some years on the 750's. Looked and could not find anything and it may just be a case of too many beers over too many years   

[Don R]

The hieght discussion was in the Ebay 836 kit threads. My piston and someone elses ended up above the deck a bit while some were in the hole a few thou.