, you've got an interesting thing going on here. I'm moving it to its own thread for better visibility.
Yeah, I thought of that when this started.
Any Ideas as to what / why the 688 piston burned & scored?
Well now that's a very good question. I tried remembering back to all the engines I've worked on, and I asked around and had all kinds of stuff thrown out there. But in the end it was running when I tore it down, and was just noisy like a tractor should be after a long season. (I'm making myself feel better saying that)
Engine Dynamics over in Petaluma CA looked at it and said it looked like I ran it out of oil. (Like he's never seen that before with a KLR)
But after the rebuild, it never used oil and I was checking it at every fuel stop and it was full. I changed the oil before I left on my trip, and then changed it again in Guthrie Oklahoma after about 2,500 miles. It was right before that in Texas that the "noise" started.
So my conclusion is that it might have been thinned out oil which was definitely the case when I drained it. BUT... Michael did state that they have seen engine failure (premature wear) on KLR's that have been used for long highway hauls. I guess there's something to watch out for, running a lawnmower at 75 MPH for 300-400 miles a day. But Michael over there (great vintage British mechanic/machinist) did say that he was amazed about all the stories he hears where those KLR's go. "Ride the bloody things around the world, they do."
Also, when I pulled the timing chain out, the tensioner was almost at the end showing that the chain was stretched. And after 55,000 miles of good riding, I just figured to replace both chains while I was in there.
(and maybe, just maybe, use that as a selling point if I start looking at another ride with one more cylinder and another gear)
UPS just showed up with the second box of parts, but the wife wants to go over to the coast. So we're packing up the trailer and heading for Bodega Bay for a couple of days camping and I'll stop in Petaluma on the way home to pick up the head.
Maybe I'll have the new cylinder and piston waiting for me when we get back.
I'm hoping for some good fall riding when I get this back together.
Remember though................................ no matter what happens, what breaks, just keep it running so you can ride.
Get out there and ride. It's amazing where you can wind up.