Cam Install help -- rebuild Tech needed

[dardoonk]

I'll give the details of how I installed the cams, tell me where I might have gone wrong; or if it makes a difference. - Bike is a '77 GS750B

> Timing at TDC for #1 piston.
> Installed EX cam first - the #1 is pointed directly to the side of the head & the #2 mark is pointing directly up (in relation to the head). There is no slack in the camchain between the crank and the EX cam gear.
> Installed the IN cam with the #3 mark pointing directly up (in relation to the head).
> I counted 6 times to make sure that there are 20 pins from the #2 mark to the #3 mark. And, just like in the manual, the lenght of 20 pins, including the pin over each marked tooth creates a straight chain between the two cams.

This is where I am screwed up...
> At this point, I still have the vice grips holding down the IN cam and have tightened the cam bolts to the correct torque setting. Everything is as described above & matches the pics and description in the books exactly.
> When I remove the vice grips, the IN cam rolls forward about 1/2 tooth. It does not skip a link and I still have 20 pins between the #2 & #3 marks, but now the cam chain in slack.
> When I install the cam chain roller on top of the head, the IN cam moves forward again by another 1/2 tooth, but I still have the same 20 pin spread.
> Is this a problem?? The exhaust cam never moved. I am assuming that valve spring pressure against one of the IN cam lobes was just enough to rotate it.

So, I have the EX cam perfectly aligned, 20 pins between the #2 mark & #3 mark, but the #3 mark does not point exactly where I expected it to. I suppose at worst, my intake cam is a little advanced, or maybe it is not??? If this is not going to cause the valves to crunch, how does this affect performance.

[chef1366]

A little trick I do is put the cam caps on the exhaust cam (in time of course) and before putting on the intake cam caps I release the cam chain tensioner while holding the chain on the intake cam sprocket so it doesn't jump any teeth. I then put on the intake cam caps. Count the links and then turn the crankshaft a few times and recheck the timing.

[Nessism]

You might want to put all the cam caps on and spin the engine over (with cam chain tensioner installed and the plunger released). Go through two revolution of the crank and realign the T mark on the crank while watching where your #1 mark is relative to the top of the head. It's normal for the mark to be off a little (1/2 tooth). You need to align the cam so you get as close as possible but it will not be perfect. Intake cam is aligned relative to the Exhaust so that part is easy.

Good luck.

[bwringer]

The missing part of the equation is that you have to install and release the cam chain tensioner. Rotate the engine through two turns and re-check.

[dardoonk]

I did leave the cam tensioner off my description, but I did install it before rotating the engine. Actually, this was my final step after installing the tensioner & the chain roller gear that sits between the cams. Also, the cam was in this position before I installed the tensioner. The engine rotates fine and I come back to the same marks each time.
Here is a picture of the cam at TDC - and I still count 20 pins between the cam marks.

[dardoonk]

Here is a pic of the end of the cam. From what I had read, this notch in the end is supposed to point as it shows.

[Nessism]

I did leave the cam tensioner off my description, but I did install it before rotating the engine. Actually, this was my final step after installing the tensioner & the chain roller gear that sits between the cams. Also, the cam was in this position before I installed the tensioner. The engine rotates fine and I come back to the same marks each time.
Here is a picture of the cam at TDC - and I still count 20 pins between the cam marks.

How does the exhaust cam position look with the T aligned on the crank? Is the hash mark level with the gasket surface.

[dardoonk]

The Exhaust cam appears to be set perfectly. #1 mark points directly at the gasket & the #2 mark is also spot on.

[chef1366]

Now on to the next step.

[dardoonk]

Now on to the next step.

So, your saying I've got this right?

[chef1366]

From the pics I couldn't say. From your description Yes.

[Nessism]

So, your saying I've got this right?

I support Chef in saying that based on what you are saying, it seems right. The key is to have that T aligned on the crank indicator and the #1 mark pointing at the gasket surface. Then it's a simple matter of counting the links between the #2 and #3 marks on the two cams.

You should take some time to get the valve clearances right at this point. Follow the procedure in the manual - it's important to have the cam in the proper position to assure the adjacent cam lobe to the one you are checking is not compressing the spring which will skew the cam within the journal clearance. Some people make the mistake of just getting the lobe pointing away from the spring thinking this is good enough.

Good luck.

[Steve]

My only question is on the count. You keep saying "I still count 20 pins between the cam marks". In my manual, it says that the pin above the #2 mark on the exhaust cam is counted as #1. #20 will be over the #3 mark on the intake cam. Counted this way, there will be only 18 pins between the marks, but 20 including the marks. The book says you should include the marks.


.

[dardoonk]

Steve,
I've mis-worded that and thanks for noting. I am including the pin above each tooth when counting. Counting the pin above #2 mark on the EX cam, the 20th pin is above the #3 mark.

I am going to remove the roller gear (or whatever it called) on top of the head, re-install the cam chain tensioner and double check everything on Friday evening.

[chef1366]

The crank trigger needs to be pointing at the 1&4 side with the T lined up as well. That way the #1 cylinder is at TDC. The #1 cylinder should be at this point at the top of the cylinder.