Timing Chain Issues - 650

Hey gang. It's been a while since I had the head off my 650 and brought it into the machine shop to get them to give it the once over.

Putting the head back on after a valve adjustment and setting up the cams I found this issue. As I mentioned, it has been a couple of years since I had the 810 built and I want to check to ensure that I haven't screwed up anything before I light 'er up.

Here is a little background info.

1977 Kz650 bottom end. 750 jugs bored out to 810. Gpz750 cams, intake valves. Stock roller chain, APE cam chain adjuster.

Set the ignition mark to 1-4 setting with cylinders 1/4 at TDC.
Lined up the exhaust cam to the head surface, same on the intake cam, counted 36 pins backwards from the correct marks and ensured there was no kinks in the chain. Torqued down the cam caps.

Installed the top cam chain guide and pushed down to make sure the slack was taken up.

Turned in the APE adjuster to where it was touching the chain and backed out 1/4 turn.

Now when I roll over the engine with a socket on the 17mm bolt, the engine turns over nicely but a couple of times in the manual rotation the chain slightly drops under the top cam chain adjuster. It almost makes a popping type sound when the chain drops. The chain doesn't jump a tooth as the marks are still lined up on the cams when the 1/4 ignition marks on the points plate are lined up.

All the shims are in place under the lifter buckets and the plugs are out when I am rotating the motor by hand. Nothing looks out of place on the top end.

The bike has only about 20,000 miles on it and when I checked the cam chain stretch the links were still within the factory tolerance levels.

So any pointers on why the chain might be dropping? Is this normal?

Cheers-Colin Firth-Ontario Canada

I think there's still some slack in the chain.
Mark

Thats kinda what I was thinking. Or maybye one of your Idler wheels (for the camchain) is starting to go, causing excessive slop?

good luck:)
MAC

sounds like loose cam chain to me as well take it back to tdc on no'1 then readjust your cam chain tension again.

Thanks gang - APE tensioner is installed properly. I am leaning towards Mark's suggestion. I pulled the chain tight then rolled it by hand probably only ten links before I started setting up the cams. This time I am going to get my son to turn the 17mm socket and complete one full revolution of the engine back to the 1/4 marks while keeping the chain taut up on top.

I'll let you know my diagnosis of my flub which was quite likely a result of just rushing to get everything buttoned up and fired.

I know this motor inside and out but once in a while everyone of us makes a rookie mistake:-)

Cheers-Colin Firth-Ontario Canada