Exhaust Valve Leak - Defective Valve?

Hey guys, I picked up a second XJ1100 a while back in near perfect condition, however also knowing it had a bad cylinder. I finally have time to work on it and what I found seems a little odd to me. Here is a quick rundown:

Compression test showed zero psi on cylinder 2, all others are perfect (not even 20k on the clock btw). Head gasket looked fine (no leak or blow out) and cranking with the #2 plug out definitely pushed some air out the plug hole. I pulled the valve cover and checked clearances thinking maybe the clearance is so tight the valve isn't fully seating. What I found was that all valves were tighter than spec except the exhaust valve on #2 had a huge clearance, about 0.5mm, double the spec clearance. Now I know something is very wrong so I popped a scope down the plug hole to inspect the piston expecting the worst but it looked fine, no holes, no cracks, nothing foreign in there. Relief! Next I pulled the head to inspect the valves. Sure enough exhaust valve on cylinder 2 is not seating, pouring oil in the exhaust port leaks straight through the valve. I thought maybe a chunk of carbon or something was wedged in the valve seat somehow but after removing the valve and spinning it in the guide I can see that it's actually just warped/bent, basically the valve moves slightly eccentrically to the guide. Visual inspection of the valve stem shows a very slight bend at the seating end. The valve shows no signs of impact from what I can tell and neither does the piston (cam chain is intact and timing was correct btw)...

Any ideas what could have caused the valve to warp/bend? Is this something that can happen when a valve overheats? Or could the valve be defective? (Uneven heat treatment of the metal?) All other valves seat and seal fine (I'll also be lapping all of them while it's apart).

At any rate I know I need a new valve now, just curious to hear some thoughts and if anyone else has experienced anything like this.

Cheers,

Trev

 

Also, something interesting I noticed was how much more carboned and downright gritty the intake valves were than the comparatively clean exhaust valves.

 

Bingo.

It certainly is. "Can" being the operative word; doesn't always happen but it sure can.