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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
Dave
685 tear down due to oil burning
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A quick question - should I get the sleeve measured to see if it's still round,
I ordered it all from schnitz racing.
It was a local machining shop, they were recommended to me I believe.
I recon that you didn't read post #20.
Saw that. Would I need to take in the piston, and the boring instructions as supplied with the 685 kit?
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That top ring land is pretty clean for there to be that much oil coming from below the rings. The chamber is dark as is the 'oil wash' coming from around one of the intake valves which is what leads me to believe it's stem seals.
As the OP stated it smokes right on start up. Leaky seals are going to allow oil to pool up behind the intake valves or into the chamber if it stops when the intakes are slightly open. Most of the 'oil wash' I'm seeing is concentrated near the center of the chamber and one intake valve which leads me to believe that's the source.
You just need to have the machine shop check concentricity top and bottom to verify roundness. As stated previously, have them lightly hone it to reinstate the cross hatch pattern. If they have a 'plateau' hone to finish it even better. It'll aid in oil retention and ring life.
Best wishes
As the OP stated it smokes right on start up. Leaky seals are going to allow oil to pool up behind the intake valves or into the chamber if it stops when the intakes are slightly open. Most of the 'oil wash' I'm seeing is concentrated near the center of the chamber and one intake valve which leads me to believe that's the source.
You just need to have the machine shop check concentricity top and bottom to verify roundness. As stated previously, have them lightly hone it to reinstate the cross hatch pattern. If they have a 'plateau' hone to finish it even better. It'll aid in oil retention and ring life.
Best wishes
I personally would NOT dismount the JE/Schnitz piston. Very stiff/obnoxious pin clips which should NOT be re-used.
If the cylinder bore has less that .004inch of Extra bore Diameter than Schnitz instructions suggested bore size I'd re-ring it and ride it. I'll bet that it has less than .002inches of extra clearance.
You can still see the hone pattern, correct?
Yes, I can still see the hone patterns. There are two spots in the cylinder however that I can't see the hone pattern. Small, 20mm round I'd say, and centre (vertically) in the sleeve, one on the intake side, one on the exhaust side.
I had a closer look at the bore and the piston, and there's potentially a few concerning developments. Photos attached.
There's scoring on the piston, and the bore vertically. I can't actually feel any ridges on either.
Bore also has a spot where it's smooth.
Should I be concerned about this?
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There's scoring on the piston, and the bore vertically. I can't actually feel any ridges on either.
Bore also has a spot where it's smooth.
Should I be concerned about this?
Oh bloody phew, I was crapping myself!
Thanks. I actually have a thermo bob kit, never put it on. Really I guess after the 685 kit I was a bit wrenched out. I'll be putting it on this time though!Tom Schmitz tells/told us that this piston from his personal bike was still RUNNING quite well.
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Again I'll suggest a light hone & new Rings. Eagle Mike also sells the Thermo-Bob, if you so desire or afford a little extra expense.
Um, I ordered 685 rings from schnitz, but I think I originally got my 685 kit from eagle mike (not sure, still digging). Are the pistons the same? I'm assuming so.
Edit: Ok never mind, I can see I originally bought my 685 from schnitz, so all good - phew!
Edit: Ok never mind, I can see I originally bought my 685 from schnitz, so all good - phew!
I got the calipers out for a rough measurement of the bore (before the bore gauge turns up).
Measuring the top of the cylinder, front to back: 102.50
Measure the top of the cylinder, side to side: 102.50
Measuring the bottom of the cylinder, front to back: 102.49
Measuring the bottom of the cylinder, side to side: 102.30. Eek, that doesn't sound good, by my reckoning that's 8 thou of an inch out.
That bottom measurement is for the bottom of the sleeve though, so prob 30mm higher is where the rings actually stop, and the sleeve is thicker there I believe.
Measuring the top of the cylinder, front to back: 102.50
Measure the top of the cylinder, side to side: 102.50
Measuring the bottom of the cylinder, front to back: 102.49
Measuring the bottom of the cylinder, side to side: 102.30. Eek, that doesn't sound good, by my reckoning that's 8 thou of an inch out.
That bottom measurement is for the bottom of the sleeve though, so prob 30mm higher is where the rings actually stop, and the sleeve is thicker there I believe.
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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
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
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?
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