Topic: CB650 Engine rebuild

[Jbosma]

OK so I've been working on doing a top end rebuild for my 1981 CB650 and im on the installation now. Im currently having an issue where I can't get the cam sprocket on the shoulder of the cam shaft where it needs to be. I have the cam chain tensioner bolt torqued down to 10ftlbs as per the manual and I can even get the cam shaft seated in its journals but can't just get the sprocket (with the chain over on it) over the cam shaft. I pulled out the cam shaft and sprocket from the engine just to see if it does actually go on correctly and it certainly does go on this cam shaft shoulder and fits very nicely when I have it out off the engine.

thoughts?

[scunny]

With a new cam chain on my 650, I had the same problem.
step 1. make sure the tensioners lower end is in it's groove, you can verify by having the oil pan off and lying on the ground in my case and shining a torch up.
put chain on sprocket and lever it into position.
check alignment.
I don't know why but, that's the only way I managed. 20,000 KM's later every thing is still good.

[Jbosma]

ok ill give that a shot and upload some pictures of the tensioner today.

[Jbosma]

So I removed the oil pan and from what I can see it looks like the tensioner is not rubbing against anything and is seated correctly. Its very hard to get some decent photos but from what I got, I think you can see that it is infact not rubbing against anything. So where does this leave me? I've heard of some people sticking a screwdriver down and pushing on the tensioner to release even more tension. Just don't know if thats such great idea and I don't want to break the tensioner, although I do want to get this engine put back together...
let me know what you think from the photos, I also attached one with a view of the entire gear assemblies does everything look good? (I have the strainer removed for cleaning)

[DaveBarbier]

I do use a big flat head screw driver to push the tensioner flat to relieve pressure, then tighten the tensioner so it stays put. It does seem like your tensioner is in the right spot so I would lever up the sprocket and chain on to the cam shoulder. That’s what I did with my 550 and 650. You should only have to go up like a couple millimeters.

[CB650CPastor]

OK so I've been working on doing a top end rebuild for my 1981 CB650 and im on the installation now. Im currently having an issue where I can't get the cam sprocket on the shoulder of the cam shaft where it needs to be. I have the cam chain tensioner bolt torqued down to 10ftlbs as per the manual and I can even get the cam shaft seated in its journals but can't just get the sprocket (with the chain over on it) over the cam shaft. I pulled out the cam shaft and sprocket from the engine just to see if it does actually go on correctly and it certainly does go on this cam shaft shoulder and fits very nicely when I have it out off the engine.

thoughts?

Man, that cam lobe in the third picture looks pretty knackered. I don't think I would install that.

[Jbosma]

Was able to finally get it in! Using a large screw driver did the trick. Cam lobes looked only rough in the pictures because I had pulled it out of the freezer and that was frost on the can shaft.  Can shaft is actually in pretty good shape.

[DaveBarbier]

Was able to finally get it in! Using a large screw driver did the trick. Cam lobes looked only rough in the pictures because I had pulled it out of the freezer and that was frost on the can shaft.  Can shaft is actually in pretty good shape.

Why was the cam in the freezer?

[Jbosma]

Cam was in the freezer because so it would shrink making it easier to fit into the sprocket. Yeah I doubt this actually works but I’ve seen many people do it and sometimes It works out well. Seen it done on a couple cl350