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Lost Valve

When a valve adjuster lock nut doesn't stay where it's told to, any number of problems can arise. Unfortunately, the  error and its result are out of all proportion to each other. Any one of us could have done the same thing. If you think that the torque according to the manual is too high, then take your chances. Play it safe and buy a spare adjuster or two and get those nuts really tight next time. If you don't use a torque wrench then use a short box end wrench and lots of muscle.
This is what your bike will look like half way through an engine swap. The rear wheel had to come off as did the drive train in order to move the swing arm back. This took three of us about 4 hours.

The first clue that the problem was top end and not the bottom end was bits of metal in the #1 carb outlet side. The metal in the #1 exhaust header confirmed it.

Unfortunately the picture of the spark plug didn't turn out but the end of it looked just as bad as the piston. When Gene tried to remove the plug, it was obvious that something was wrong from all the resistance that it put up. The center electrode was bent and the tip was all chewed to rat shit. This was our real proof .

Since I can't show you the plug, here's a valve and part of its seat.

Once the valve cover came off, more clues emerged.

The lock nut and adjuster bounced around the upper area of the head and eventually got in the way of one of the rocker arms.

Adjuster 1, Rocker arm 0

Here is the business end of the head. That valve at top is just the end of it. If it appears to be lying 90 degrees to the seat, it is. We found a piece of the stem which was maybe 3/4" long, and it was bent.

 That light colored stuff in the combustion chamber is actually tiny bits of piston. When the valve hits the piston a few thousand times, it tends to shorten its designed life a bit by removing all those little bits. The little bits then melt and adhere to the combustion chamber. What didn't stick there ended up in the exhaust pipe and carb. Some of that was magnetic and was presumably part of the valve stem and maybe one valve keeper that we never found.

This is the #1 piston. Now you know where the aluminum in the combustion chamber came from.

 By the way, that object that you can see through the hole in the piston is the connecting rod. Don't know what kind of shape it's in. The cylinder was scored but there was no metal visible in the oil filter. So the jury is still out on the cylinder and bottom end.

At the risk of stating the obvious, the piston on the left is what it should look like.

After a huge day and a half effort, the new engine was in; cracked head and all. Pissed oil from a crack around the engine mounting bolt hole on the left side of the head. The crack must have occurred when the donor bike crashed.

Sherri was fortunate enough to locate engine number 3 in fairly short order. This became the donor for the head which was swapped the following weekend.

On the second trip to Gene's, the head came off engine number 2 (donated by Steve Mustoe). Sherri puts her dental hygienist's expertise to work here. Can't you just hear the poor engine writhing in pain ??? Floss next time, damn it, floss !!!
These intake valves came out of engine number 3. Gene quickly deduced that it was a 1986 engine by the tuliping of the valves. Look at edge of the valve on the left where it mates with the valve seat. It has a noticeable concave curve to it and the edge is very sharp. Our resident expert figured they would have given up the ghost in another 10,000 miles or so. You can also see a huge buildup of crap on the backside ( there's a pun in there somewhere ) of both valves. They were all like that. By comparison, Sherri's original valve were in beautiful shape if you ignore the fact that a couple were hopelessly bent and broken.

Article By: David J. Morrow

Updated January 2005 

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