engine rebuild problem: valve "slap"?

Bicycle Lee wrote:

I guess my big-dumb question now, is: HOW THE HELL DID MY VALVES GET BENT JUST FROM SITTING THERE???

Bicycle Lee wrote:

Got up to the cylinder head assembly and installed the cams, making sure to follow the manual at every stage. Once the cams, upper cam chain guide and cam tensioner were in I decided to turn the crank to see how everything worked.

Bicycle Lee wrote:

I did not adjust the cam tensioner. How do you do that? Adjust the lock bolt??

In 1980, on a 77 KZ1000, I made the most expensive mechanical related, mistake of my entire career.

I followed the (mistaken) instructions in a brand new Haynes Manual, I loosened the lockbolt on the tensioner, spun the motor over twice by hand, just as stated in the Haynes Manual. When I stopped to re-position the wrench, the cam chain dropped off the crank sprocket and bent the valves.
This took place in Germany, and it cost me $1500 in 1980 dollars for a new head.


I think there is a good possibility that you just repeated my long ago mistake.

yeah, I'm starting to realize that...


but I shouldn't need a new head, right? Just valves?

My guess is you are using the wrong timing marks on the cam sprockets. I had the exact same thing happen. I did my rebuild, put the cams in with marks aligned. (That's where the mistake is, the marks you think they are referring to are not the correct marks), turn the engine over slowly, hear a "click, turn it over a little more, "click. Of course after about 4 clicks I knew I was in big trouble and had all 4 intake valves bent. The valves butted together when turning the engine over and each butt was a click So look again and make sure, easy to get mixed up. A lot of valves have been bent on KZ1000s from this mistake.

so WHAT marks are correct then? I was referring to the ones in the Clymer manual.

SO I pulled the head back off and looked at the valves. The intake valves had a little notch in them on the side facing the exhaust valves, indicating that they had been contacting each other....
What's THIS all about?

No doubt then you did the exact same thing I did and used the wrong marks. If you have the same Clymer manual I have look at page 91 which I'm sure you already have, but look at the picture carefully and make sure everything on your bike looks the same, like where the bolts are orientated on the sprockets to make sure you're using the right marks. It's been close to 20 yrs ago I made this error and I think I used the wrong arrow on the exaust is where I did wrong.

I really can't understand how I used the wrong marks. I used the lines which are embossed on the camshaft sprocket. How CAN those be wrong when they are the same ones the manual tells you to use?
Does position of the bolts determine how to get the cams in correctly?

On mine there was marks that appeared to be the right marks, but other less correct looking marks that were in fact the correct ones so look for other options and compare with the picture. On mine after I bent the valves and looked at the pictures I could see my camshafts were not positioned as the picture by the fact the bolts and cutouts ect in the sprocket did not look exactly like the picture and in fact another line was the mark to go by. Good luck.

Bicycle Lee wrote:

SO I pulled the head back off and looked at the valves. The intake valves had a little notch in them on the side facing the exhaust valves, indicating that they had been contacting each other....
What's THIS all about?

That's how the valves get bent, they don't contact the pistons, they hit each other.

I doubt that you will need a new head, I was in a situation where I "had" to have the bike running, and time was of the essence, replacing the head was the fastest way to fix it.

BL... if I might suggest... we have a valve clearance article on our website. It might be of help. The exhaust cam is lined up first. There is a mark that looks like an arrow on the edge of the sprocket >

This arrow will generally not point EXACTLY at the gasket mating line in front. Will point slightly above or below but if you get this mark to where you can't get it any closer, it will be correct. You then start counting the FIRST rivet above this mark. It will be #1 (as opposed to zero) and count on the chain from the right side of the bike 28 pins. You then yank, tug, wiggle the chain to ensure it is tight on the crankshaft sprocket. Then put the intake cam in place where the 28T | mark (the vertical mark next to the 28T lines up with the 28th pin.

What I would personally do is find another cylinder head on eBay. I would disassemble, clean and lap the valves and check for play in the guides. They are 7mm holes which is about 1/4" and the valves fit in the guides fairly snug so you shouldn't be able to rock the valves much. I would pay attention to what shims are installed and where and if any are skinny; that is, below 225, pay special attention as the head is worn pretty good. It will be cheaper to pick up a complete head than purchase new valves, get the valves ground and get the seats dressed on the old head. I keep a few spare heads that have been gone through and checked out for this reason.

wanna sell me one????
I looked around on ebay and couldn't find one that fit.
I was going to use my stimulus check to get the bike painted but it looks like I'm going to be getting THIS taken care of... goddamn I'm getting very angry with this.

edit: I just looked at my exhaust cam and there is no arrow > on it. It is a three bolt sprocket and the only marks are: the two lines that are SUPPOSED to be the ones you use, a #20, the word "EX" and a couple little circles... all which seem rather innocuous compared to the matching lines....

When I did mine new valves were only $15 each. Did you figure out where you went wrong? Be sure before assembling again.