Cam Chain Timing Help

[Guest]

Finally got the time to fit everything together from replacing the head gasket. Got to the point of installing the cams and tensioner and I don't think I've quite got it.



It's an '80 850GL. The pink line is the arrow indicating the 1 mark and the yellow is the gasket surface. (White specks are paper towel lint. I plan on an oil change after sych'ing the carbs.) The manual says while installing the cam, it should be pointing to the gasket surface. It was when I installed it, but after installing the cam chain tensioner and idler, this is where it sets.

While the tensioner functions correctly while I've got it outside the motor, it doesn't seem to be holding the right tension when installed.

As I spin the motor by hand, there is a slack section that travels in the same section of chain. I don't know if that makes sense, but what happens is the chain holds tight against the idler until this section comes up and then it sags under the idler.

Any help on these two items would be appreciated! I'd like to have the bike together this week to enjoy the fall. I've been sans bike for about 6 weeks.

[Nessism]

Looks like you need to retime the cams, that hash mark needs to be flush with the valve cover surface - looks to be off one tooth. Before you take the cam loose, mark the chain in the same spot as your yellow mark in the photo. When you put the cam back in, just align the mark with the #1 mark on the sprocket and you will be good.

Regarding the tensioner, it's normal for there to be a slack spot in the chain when you turn the engine with a wrench. Just make sure the tensioner is working properly and you should be good.

[Riding Again]

Thanks. I'll give it a go. The chain tension was quite worrisome. The chain clicks as it sags and retightens against the idler.

[Nessism]

Did you release the plunger after you reinstalled the tensioner?

[Riding Again]

After installing the tensioner, I backed off the nut and turned the screw about 1/4-3/8 counter clockwise, then retightened the nut.

[GS750]

Looks like you need to retime the cams, that hash mark needs to be flush with the valve cover surface - looks to be off one tooth. Before you take the cam loose, mark the chain in the same spot as your yellow mark in the photo. When you put the cam back in, just align the mark with the has mark on the sprocket and you will be good.

Regarding the tensioner, it's normal for there to be a slack spot in the chain when you turn the engine with a wrench. Just make sure the tensioner is working properly and you should be good.

I know Im jumpin in a bit late on this but heres my reply:

The cam timing issue seems to be a regular thing. I found that my cams were actually 1 tooth out (same as the O.P's picture) and after I reinstalled my barrels, new pistons etc (wiseco 850BigBore kit) I stuck the cams in and was tightening them up, decided to check them and I was exactly the same as in the O.P's picture.

I have since discovered 3 other 750 and 850's with this exact problem.


With the tensioner, I also found that using some black molybdenum disulphide grease during re-assembly really helped! I didnt replace anything other than the seals on mine and it is working like a charm!

[chef1366]

Are you on TDC during that pic?

[psyguy]

the pic you posted and the marks on it are relevant only while setting the chain/cams with the ignition plate at tdc mark (and relative to the other sprocket that is not in your pic)
if the whole lot moves a tooth or so after the chain is correctly placed on both sprockets then it doesnt matter

[Riding Again]

I was at TDC for install, and also when the picture was taken. I reset the cam timing per Nessism and redid the tensioner.

After those redo's I spun the engine again and the cam lined up properly along with a quiet running chain. The chain didn't sag or slap.

Finished up with firing it up a couple nights later

[rphillips]

It's not been mentioned, but when installing the cams, you must keep the slack in the cam chain toward the back of the eng. all during instillation. If the slack is toward the front, when the tensioner is installed the cams will turn appx. 1 tooth backward thus being as in first picture, 1 tooth retarded.