Jdub goes there 1981 650e rebuild

[rphillips]

Well, it's amazing how many folks in machine shops don't know much about motorcycles. Guessing they did get the surface flat, just a little too low, and never had clue they messed up.

[1978GS750E]

I now think I know why I have binding on the camshafts.
The machine guy I had repair the damaged valve cover bolt threads, said he decked the top of the head also because of scratches resulting from attempts to remove the broken bolts.
I cleaned up the journal bearings and cap surfaces with wd40 and 5000 grit sandpaper. I can finger tight the bolts and the camshafts still move with a small amount of resistance. As soon as I tighten them up further, the camshaft wont budge.
So close to the finish line.

20240823_200258.jpg

Any reputable machine shop would know better than to do that!

Your "machine guy" should be buying you another head IMHO!

[Rich82GS750TZ]

The way I understand it is the cam journals/caps are line bored together from the side at the factory, so each set of caps is mated to the exact position in a specific head. Well you've got practice at cleaning up and painting engine parts. What's one more head? Now to find a good used head w/ caps.

[jdub6092]

Even if I could somehow hone the journal and cap bearings to freely spin the cams, I'd be looking at a full set of thinner shims and no guarantees.
I can clearly see that the caps can rock to either side with the cams installed. I measured a 0.33mm gap when pressed down flush on one side, so I'm about 0.165 mm from the cap being flush to the surface.
If I had the bearings honed evenly, the camshafts would drop down by about 0.08mm. With my smallest shim being 2.55mm, that would become a 2.45mm shim if my math is correct.
The question is how would the journals respond to the additional 0.16mm gap?
I saw a discussion where a gs450 owner had the same issue, but thinks he lost enough material by using a brush tool designed for gasket removal. He ended up replacing the head.

[Rich82GS750TZ]

Ooh, that’s too bad. I don’t know how you come back from that. The removed material from the top of the head is now making your cam caps pinch the cams tight and your cam journals are no longer in aligmnent. Others may have some better advice. I think I’d be looking for a new (used) head complete with cam caps.

[jdub6092]

I now think I know why I have binding on the camshafts.
The machine guy I had repair the damaged valve cover bolt threads, said he decked the top of the head also because of scratches resulting from attempts to remove the broken bolts.
I cleaned up the journal bearings and cap surfaces with wd40 and 5000 grit sandpaper. I can finger tight the bolts and the camshafts still move with a small amount of resistance. As soon as I tighten them up further, the camshaft wont budge.
So close to the finish line.

20240823_200258.jpg

[jdub6092]

I pulled out the valves and wanted to see how the camshafts turned without resistance.
Well, turns out that the journals on both are binding. I cant budge them when the holders are snuggled down. 1/4 turn back on holder bolts and they do rotate, but the exhaust side is still a little sticky.
Could bead blasting have contributed to this?

[jdub6092]

I followed the manual except i counted out 20 link pins instead of 19. Bolted the holders down evenly, exhaust side first. Then intake cam allowing some slack. Then I installed the tensioner.
Rotated the crank one turn until slack between cams was removed, but it isn't overly tight.
Then I torqued down the camshaft holders and couldn't turn the crank anymore. I lubed the journals and bearings generously.

20240817_200004.jpg

[rphillips]

How tight is the cam chain? you did loosen it didn't you? thinking that may make a difference

[jdub6092]

Went with the above. Doesn't matter. Can't turn the crank with camshaft holders torqued down. It rotates when the holders are backed off a couple of turns.
I knew there would be days like this.

[jdub6092]

I think I answered my own question. The manual is not correct as it is listed as links 1-20 on the GS650G manual as well as several other models.
The manual also doesn't seem to match the timing marks. It shows text that doesn't match the timing plate and then shows two different sides of the T to line up.

I'll just ask if this is the correct alignment of the timing mark for TDC?

20240817_073317.jpg

[jdub6092]

Thanks rphillips. I cranked down the holders at the synced position.
Now I'm counting cam chain links and my manual says 19 link pins between the vertical arrows on the sprockets (link pin 1 lines up on the exhaust side and link pin 19 on the intake so actually only 18 links between as I read it).
Well, this causes the intake arrow to rotate toward the exhaust side and I have not replaced the cam chain. If I adjust by one link (1-20), both arrows are vertical and the chain is quite taut.

I've watched a few GS550 videos and see that they indeed use 1-20 links. From what I understand, the GS650E is just a bored out version of the 550, so is it possible that the manual is not very precise and possibly means 19 links between alignment arrows?

[rphillips]

There won't be a place where a lobe is not on a bucket or rocker, depending on the bike. Check the manual, you check half the valves with cams in one position and the other half with cams in opposite position. If there was a place where no lobe was contacting, you'd set the cams at that point and check all at the valves without needing moving the cams.

[jdub6092]

Trying to get Cams installed.
I noticed that the initial positions with arrows aligned per manual do not allow the journals to seat. There is a cam lobe that is just contacting a shim enough to raise the journal from the bearing surface. Appears to be the case on both cams. Is this normal?

[rphillips]

This cam thing got me wondering, so looked it up. It says the hardened surface of the cam should be min. of 2.54mm. So, like he ^^^^ said, your 0.4mm should be of no concern.