Valves "Unadjustable"

[rcacs]

Originally Posted by AncientMariner

Good pics. Obviously, the Volkswagen mode of valve failure doesn't apply here. No sign of "necking" on the stems. The yielding must occur closer to the head of the valve, to belabor the obvious. I know nothing, as Mort so graciously observed. I still wonder at the undersized stems, though. Not the result of wear?

If you are referring to the area where the stem gets narrower, that is just the way pretty much any valve is made.

[Sleepy8driver]

Originally Posted by rcacs

No sealant is used on the head gaskets. Just ensure everything is clean as a whistle (but I'm certain you already know that).

Cheers

Thanks for the confirmation.

[Sleepy8driver]

Originally Posted by AncientMariner

Good pics. Obviously, the Volkswagen mode of valve failure doesn't apply here. No sign of "necking" on the stems. The yielding must occur closer to the head of the valve, to belabor the obvious. I know nothing, as Mort so graciously observed. I still wonder at the undersized stems, though. Not the result of wear?

I was thinking the valve stems are thinner than they should be because the valves had stretched as a result of overheating. That would account for the minimal clearance I was getting when I tried to adjust them. I will know more when the new valves arrive and I can measure and compare.

[AncientMariner]

Originally Posted by rcacs

If you are referring to the area where the stem gets narrower, that is just the way pretty much any valve is made.

You know how a sample piece of steel that's in a tensile strength tester necks in just before it fails? That's what the remaining valve in my VW looked like. It sorta made sense to me that the loss of strength from excessive temp would cause failure where it met the smallest diameter, highest stressed, spot, the head-end of stem. Maybe the VW exhaust valves had flatter heads, less tulip shape, allowing extreme heat reach the stem? I don't know what they look like 'cause I had the dealer look at the engine to see if it was salvageable. I can't buy that the whole stem would stretch evenly due to overheating of the head. I've been wrong before, though.

I'm told that when my theory doesn't match the evidence, believe the evidence and get a new theory. Apparently, the heat in the head area can be intense enough to cause yielding of the tulip area in spite of its much greater cross sectional area?

[Sleepy8driver]

Will be busy for a couple weeks but I will post when I return. Am curious about the length of the new valves.

[Mortaine]

Sleepy

Be sure you fix the cause of the high heat failure after you get the engine back together or it will do it again.

[rcacs]

Thats why I asked if he had any history on the bike. I suspect that this occurred with the previous owner, who then had the valves adjusted.

Cheers