685 Piston Identification? - Kawasaki KLR 650 Forum
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post #1 of 9 Old 09-12-2012, 02:15 PM Thread Starter
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685 Piston Identification?

So I have to pull my tank to do some house keeping this weekend and I was thinking....Thats never good. I have an 08 that burns no oil and I also have a bore scope. So the question begs to be answered do I have a reringed engine or a full on rebuild done? The work was done by the last owner so I cant really say what was done I guess. So if I pull the plug and go in with my bore scope is it possible to find markings on the top of that piston that will give me a clue? What do you all think?
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post #2 of 9 Old 09-12-2012, 03:05 PM
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Quote:
Originally Posted by moriver View Post
So I have to pull my tank to do some house keeping this weekend and I was thinking....Thats never good. I have an 08 that burns no oil and I also have a bore scope. So the question begs to be answered do I have a reringed engine or a full on rebuild done? The work was done by the last owner so I cant really say what was done I guess. So if I pull the plug and go in with my bore scope is it possible to find markings on the top of that piston that will give me a clue? What do you all think?

What markings are you expecting to find? The only thing I've ever seen on a piston is an arrow to orient it to the exhaust side. Carbon will cover that up pretty quickly though.

No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him. 1 Cor 2:9
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post #3 of 9 Old 09-12-2012, 04:39 PM Thread Starter
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Originally Posted by Spec View Post
What markings are you expecting to find? The only thing I've ever seen on a piston is an arrow to orient it to the exhaust side. Carbon will cover that up pretty quickly though.
Good question? I have built a bunch of motors and some times different manufactures use different markings or things. Like one piston might have an arrow marking dirrection some dont but have printed numbers on them or just different relief cuts or markings that might give clues as to who the manufacture was. I just figured if we had a whiz bang that had knowledge of such feature that would be good info to check for being I am pulling my plug out and have a bore scope handy. If not its all good.
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post #4 of 9 Old 09-12-2012, 05:08 PM
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Talking Measure the bore

Why not just measure the bore and the diameter of the piston?
There should be a measurable difference.
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post #5 of 9 Old 09-12-2012, 11:36 PM
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Originally Posted by pismocycleguy View Post
Why not just measure the bore and the diameter of the piston?
There should be a measurable difference.
Uh...I don't think he wanted to pull the head off, just peek through thr spark plug hole with a bore scope and see what markings might be on the piston top.
Regards.... justjeff
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post #6 of 9 Old 09-13-2012, 08:00 AM
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The stock piston is not dished like the 685, it is flat on top in comparisn. The 685 and 705 pistoms have roughly 1/4" of a lip around their circumferance with 4 half moon relief cuts for the valves. The stock piston is flat on top with the reliefs cut in it. So look for the lip

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post #7 of 9 Old 09-13-2012, 09:17 AM
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Quote:
Originally Posted by moriver View Post
So I have to pull my tank to do some house keeping this weekend and I was thinking....Thats never good. I have an 08 that burns no oil and I also have a bore scope. So the question begs to be answered do I have a reringed engine or a full on rebuild done? The work was done by the last owner so I cant really say what was done I guess. So if I pull the plug and go in with my bore scope is it possible to find markings on the top of that piston that will give me a clue? What do you all think?
Take a look at the first video in this post, at 1:40 you will see what the 685 piston looks like. It's a flat-top, pretty much like stock, except for the larger valve pockets.

T

Tom [email protected]

“Neither of the two people in the room paid any attention to the way I came in, although only one of them was dead.” -Philip Marlowe

“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte


Sting like a butterfly.
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post #8 of 9 Old 09-13-2012, 10:13 AM
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Tom, how did your kit turn out? Was it what you expected it to be? Did you have any weeping from that base gasket? What sealer did you use? I've dome many of these kits and now refuse to use that base gasket due to some weeping issues. It is a real pain if one does weep a bit so I have gone back to using the stock paper gasket with a smear of sealant on both sides of it to triple check for possible weeping. I found even finger prints would be enough to allow that comet gasket to weep. Also in your clip you said something about your second oil ring was 28thou. of a gap! That's huge.....both should be as close to 20 thou as possible. Maybe you were thinking oil wiper rings....?

Just curious on how your kit went and is now performing after almost a year...?

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post #9 of 9 Old 09-13-2012, 10:53 AM
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It's working fine. The oil loss, which the the biggest reason for doing it, has gone to nil.

I used a common tacky aircraft sealer on the Cometic gasket. It did weep a bit, but seems to have all but stopped. It's not been an issue, but the paper gasket is the way to go. I agree with your assessment, the wee bump in compression is not worth the hassle.

As to the second ring, yes, it was gapped at .028. The rationale is as follows:

"Second rings: Current thinking regarding the end gap on most performance engines is to provide a larger gap on the second ring for best performance. Testing has shown a larger second ring gap tends to increase top ring stability allowing for a better seal. This larger “escape” path prevents inter-ring pressure from building up and lifting the top ring off the pistons allowing combustion pressure to get by. Since the primary function of the second ring is oil control, you can open the gap with no adverse effect on the compression sealing of the ring pack. (There are some applications that don’t benefit from this theory because cylinder pressures are extremely high and the second ring is utilized primarily as a compression ring and not a device for oil control; these would be limited to supercharged/turbo applications.) Many engine builders have reported lower blow-by readings and horsepower gains in the upper RPM ranges with wider second ring gaps."

The KLR is certainly not a performance engine, but one can hope...

With ported heads, large valves, L-Mod, KLX needle, GSXR1000 muffler, and a slightly rich mixture, it provided modest power gains.

T

Tom [email protected]

“Neither of the two people in the room paid any attention to the way I came in, although only one of them was dead.” -Philip Marlowe

“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte


Sting like a butterfly.

Last edited by Tom Schmitz; 09-13-2012 at 10:56 AM.
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