I'm scared - sudden engine noise

I got on the bike this morning to go riding and took off. After about 4 minutes of stop/go the top end noise changed suddenly to become about 5 times louder than normal. It sounds something like excessive clearance, but amplified.

Recent work I've done was take off the head to fix a bent #1 valve that I think has been there for a while. While off, I lapped the valves, but new oil seals on, and carefully buttoned the head back up.

I put the head on, double checked all valve clearances, and quadrulpe checked the valve timing. I replaced the automatic tensioner with the APE manual one, but now I'm afraid I may have set it too tight.

I had a poor shim selection and the #3 exhaust was at its widest, .18mm when put back together. So I've have been hearing mild valve noise from that exhaust, so I know what that sounds like. This new sudden sound was simliar in quality and matched the engine timing like valve noise, but was much MUCH louder and sounded like nuts had been dropped in the cylinder or something.

I plan on pulling the cam cover and looking at the valve clearances and timing chain as well as the timing chain tensioner plastic. But honestly, I'm not entirely sure what to be looking for and would like to avoid overly exploratory surgery.

Does anyone have advice on what I can do? Is there any way I can avoid pulling the head?? Is it likely my head is junked?

Signature disappeared - 1982 KZ750N1 Spectre

Could have the locknut on the ape adjuster come loose and the plunger back off causing a loose chain? chris3

You mentioned you MAY have overtightened the new APE adjuster- it's possible to wear all the rubber off the idler if the tensioner is set too tight.You'll find a big pile of rubber bits in your oilpan. That might account for the noise-camchain slopping around. I did this once...only once,but it's very easy to overtighten it.

Coppertales had it right.

Just got back home to look at it and yup, the tensior lock nut had loosened and the chain was slapping. Retighted correctly and locked down the lock nut hard. All good - thanks guys, really scary there for a bit

I personally wouldn't crank down on that nut too much. If it backed off after tightening, drop a couple drops of blue Loctite on it or call APE and ask them for tips on what to do. Hopefully, you just didn't tighten it sufficiently when you did your work.

I tighten my only finger tight, then backoff a wee bit. That seems to work well for my scoot.

To clarify, I tightened the tensioner itself this time by backing off the tensioner bolt until I heard chain noise, then back in 1/4 to 1/2 turn. It was the lock nut, the one that goes flush against the tensioner that I tightened harder this time. It it is staying put now, should I still consider the loctite?

Loctite would help but how about a good old fashioned lock washer? They've worked for many decades.

Due to the construction of the tensioner, I don't know how I could add a lock washer on. The two ends of the tensioner are not accessible/removable to add anything new