Busted Valve Shims

I recently changed the head gasket on my 1984 kz550. After I put it back together I got one cylinder missing. I had a mechanic friend look at it and he brought back a cup of busted metal and said that we evidently messed up something to do with a valve shims because a couple of them shattered and one of the valve stems is mushroomed. The mechanic says we need to tear the engine all the way apart and look for pieces of the shims down in the engine.

My question is where could the shims pieces go? How could they get farther down in the engine than the tops of the pistons? We pulled off the oil pan and it seems to be pretty clean. The two cylinder walls that we can get two are smooth(not scored). And the other two cylinders have clean tops other than a little carbon deposit.

I am thinking that if the cylinders and walls don't show any signs of damage, then we don't need to tear the engine down any farther. We are going to get a second opinion on it and a quote before we do anything. If the price is not to high then we will have a mechanic do it. If it is too high then I will wait til I have time and do it myself.

What do you guys think?

I'm not too familiar with the 550s, but your bike runs shim under bucket, right?

If so I can't see how a shattered shim could go down the engine as long as all the buckets are intact and no valves are broken.

Dont think the bits would get into the cylinder. Small fragments may get into the oil-ways however and be transfered around the engine.

Fergie wrote:

Dont think the bits would get into the cylinder. Small fragments may get into the oil-ways however and be transfered around the engine.

X2 I would think when it grenaded it did not run long enough to spread the pieces

Kawickrice wrote:

Fergie wrote:

Dont think the bits would get into the cylinder. Small fragments may get into the oil-ways however and be transfered around the engine.

X2 I would think when it grenaded it did not run long enough to spread the pieces

Hopefully!!

you got plenty bigger fish to fry without taking any more apart...when you get the head rebuilt and ...and redo the cams timing and recheck the valves clearences and double check all thaty and clean and reinstall the oil pans gasket...if you can get it running do a few miles and go thru the gears and drop the pan agian...i really doubt you would find anything but some grit and such.....

you might find a low miles motor by calling around...then you could ride the summer and build the motor you have now back up as time permits.....if you put enough torque on the cams to break steel shims...you may have stretched the cam chain...hurt the tensioner and pully's....timing gears ect......what do the teeth on the cams look like?????

I'm not overly familiar with the 550 either but:

If the shims exploded they may have reached the oil returns and gone to the bottom of your motor, I think that's a possibility.
It's not likely the sump would transfer any, but some could be floating around in your oil and get to bottom end parts that way.

Since you have the head cover off you could inspect the oil returns with a light for chunks. At any rate I'd suggest taking an old magnet and drag it around the underside of your oil pan and see if you come up with and shrapnel from the shims.. it will cost you the oil in her, but it'll sure beat a chunk of shim getting between something later on.

The 550 uses shim under bucket. The bucket holds the shim onto the spring retainer which captures the shim. The retainer is large enough that I don't think there is a way for a complete shim to fall out of the bucket. It would have to fall into really small pieces then slip out of the space between the edge of the retainer and the wall of the bucket. The bucket will contain the pieces, but if they are small enough to get past the retainer, they could go into the oil paths. I don't know if they would end up in the bottom of the motor as your mechanic said.

Normally, the large oil passages will be blocked by the outside surface of the walls of the bucket, but I don't know how much of the passage way is exposed.

Here are some photos of the bucket area with the buckets, springs, and retainers removed. (There is a small silver spring there that i was using to measure cam lift.) I pointed out and circled the oil passages.

Here's another photo. As Trianglelaguna said, on a KZ550 C, you'll probably come out way ahead to just get a used motor. I've bought a decent one for $50, another for $100, and couple for free. But that will probably mean waiting til the right deal comes along.

Thanks for the responses guys

I remember when I put the cams back in and set the timing and all that we had some trouble getting the cams to go in because the journals contacted the bucket.

Maybe the bucket moved around while that part of the head was off and when I finally got the cams back on the shim had moved out of place or something and then when I ran it, it shattered?

We ran it several times since the rebuild, the longest time being about an hour from high to low rpms. At that time the carbs were out of sync and we attributed the rough running to that.

Didn't you check the clearances before you started the motor? If so, that would have showed immediately that something was wrong.

Something had to be done wrong because those shims are very well contained and are strong as hell.

Sadly, no I didn't check the clearances before I started it.

I did not do a full rebuild. The only reason I took it apart is to change the head gasket because it was slowly leaking.

I have a very good manual and I tried to follow it as well as possible but this was my first time messing with a motorcycle engine. I must have missed that part assuming it is in the manual. I know that this is a very rookie mistake and I am pretty embarrassed to have made it.

Since I didn't mess with the buckets at all(as far as i knew), I didn't think about needing to check their clearances.