The bike was just about complete. Ready for that exciting moment when it starts…or not, like this one.
I ran through a bunch of checks.
Eventually I took the valve cover off and found this little item.
Apparently, the motor spit the shim for the exhaust valve at #1 cylinder. It toasted the shim, of course, and did some other damage.
The exhaust camshaft isn’t really functional when eBay has a few at decent prices.
It did get a bit nicked up.
The tappet bucket didn’t do too badly but it will be replaced to be safe for under ten bucks.
Luckily, the cylinder head didn’t get destroyed. The interior walls got gouged a little, but no holes through the aluminum head.
The mating surface to the valve cover got slightly curled from the inside. However, the curl doesn’t extend all the way through the mating surface, maybe only less than a third of the way. So that can easily be repaired.
Now there can be lots of speculation about why/how the motor spit the shim out. In the end, it’s still speculation.
One thing that I found interesting in researching the problem was that some years ago there was a rash of breaking shims on Suzuki GS bikes. There was much ballyhoo that the shims were too brittle from the hardening process. Many linked the bad shims to K & L, so the general internet wisdom was to avoid K & L shims for the GS bikes.
Problem: There are two makers of 29.5mm valve shims – K & L and Suzuki. The OEM shims are expensive. If the motor is really out of spec, the rebuilder could easily drop close to $150 on shims.
I wonder if Suzuki makes their own shims or buys them from K & L.
In any event, it’s back to eBay to find the right parts. Then, play the waiting game and do the installation. In the meantime, I have a cool little borescope from Amazon on the way for less than twenty bucks. This will give me a look at the internals without having to remove the head (again). Hopefully, I don’t see any bent valves, knackered up pistons or any other happy surprises.
Keeping my fingers crossed at this point.