[DPelletier]

ring or bore problem; highly unlikely its the valve stem seals IMO. Check the bore....who did the original bore when the 685 was installed?

Dave

 

[DPelletier]

FYI, Here's an excerpt from Cary Aspen's notes (Cary developed the 685 kit for Schnitz Racing, RIP);

What typically happens with the bore, is that at the bottom it ovals out. It's like if you were to put your hand on either side of the sleeve bottom, and squeezed it together. It's not wear in most cases, but distortion. Usually .02-.03mm, or .0008-.0012" . A few have been worse, but .02-.03mm is what I'd call "normal" for the KLR. It's not a huge amount, and any decent ring can deal with it. The KLR's oil ring is just barely able to. It would be better not to have any warpage at all, but it's the nature of the beast, and not easily or cheaply corrected. It's due to the mechanical design of the engine.

When you bore the KLR liner, whether for the 685, or just an oversize, you are boring an already warped sleeve. So you put a nice new round hole into a sleeve that has already warped the way it tends to, or wants to. The new bore then tends to stay round. The outside is out of round, but not the new bore. Also, it's been work hardened, and is more resistant to warp from that alone. That's the reason I mention heat cycling as being good during the break-in process on a new bike. If you can harden it early, it's less likely to warp as far.

The 685 alone really doesn't change this situation. It just has enough oil ring tension to deal with it. Testing has shown that it does not warp any more, or any less with the sleeve being thinner, even when used with a new unhardened liner.

The 705 liner is differant. Every attempt was made to resist the warping that the stock liner suffers. It's MUCH thicker at the bottom, where it counts most. It's marginally thicker above that. The champher that's in the OD of the stock sleeve is eliminated. That's a key weak spot of the old sleeve. Finally, the cryo treating process makes it more stabil to hold it's shape. With a stock piston used in that liner, I don't think it would warp at all.

Cary

 

[DPelletier]

Yeah wow that's really good info thanks. So really I'm stuck with a 685 oil burner, or I get a new sleeve. Or maybe I get it bored again and it won't warp any further?

I'd suggest boring (by a good shop) with an EM 692 kit and you'll be just fine.

Dave

 

[DPelletier]

KDO: I'm puzzled by those measurements. The narrowing of the base of the cylinder from side-to-side "should" result in a lengthening of the front to back measurement. I've never heard of a cylinder shrinking overall, which is what you have indicated. If the actual side-to-side measurement is 102.30mm, the front-to-back measurement should have changed to 102.70, or pretty close to that. The only explanation that I can conceive is that the cylinder was not honed to exactly the same diameter, top to bottom, when the 695 kit was installed.

I would really like to know what measurements you get with the bore gauge.

Yep; the front to back measurement at the bottom should be more.