Cam chain, cam install question

[rwcfrank]

Hey everyone, I am assembling the top end of my 78 GS750/850 2V motor. I oriented the crank in the 1/4 T position and locked the crank from moving. I lined up the cams per the manual and counted the 20 pins. I then gently tightened the cams which moved them a bit but TDC stayed put as did the cam chain. When I began to install the top idler the orientation of the cams moved due to the chain slack being taken up. Is there anyway to double check the orientation with everything tight? I cranked it over several times and its moving smoothly. I am waiting for some shims to finish the lash so the top end is still accesible. I am stoked its getting along very well so far but I dont want to go back in later to "fix" the timing.

[Steve]

It is hard to count pins once you install the idler. If you want to re-verify, you will have to remove the idler, but that also requires removal of the tensioner.


"Cranked it over several times" and "Waiting for shims" makes me nervous.

PLEASE tell me that you are not rotating the crank unless you have all your shims in place.

.

[hampshirehog]

Line up the exhaust cam and count the pins again. As long as it's 20 from between the 2 arrows ( the 20 as per the manual) you'll be fine. If you think you are guessing how many pins are hidden by the idler put a blob of paint on each side and count the number in between after you have turned the motor so both marks are clear.

Like Steve says - don't turn the engine if you have got shims missing.

[MisterCinders]

I assume you have some shims in the buckets, and just need new shims to do a valve adjustment. If you have shims, just need thinner ones, that would be OK.

So long as you aren't running on naked buckets, here's how I check the timing. ONce you have the cams inplace and bearing caps are bolted down, install the tensioner and hand crank the engine around a few turns. Then reset to TDC and check your work. If the pins still count out right and the 1 is aimed at the head, you can add the top bit and call it a day.

Whatever you do, don't turn the engine to double check timing without re-installing the cam chain tensioner. At best, you will have to pull the head to check your valves, and re-do the timing. If you're lucky, that's all it will take. AMHIK

[rwcfrank]

Thanks everyone, I had shims in the bucket and I am certain of 20 pins (done without the idler in place), sounds like I am good to go, I will double check the pin count but I am sure its right. Thanks everyone!