Exhaust O-Ring Size

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firsthere
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Exhaust O-Ring Size

Post by firsthere »

Got a leaky header pipe with aftermarket o-rings and gasket, so looking for the exact o-ring size people have successfully used on the KDX 200 pipe. Mines a PC platinum II if that matters. Tks.
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Re: Exhaust O-Ring Size

Post by pumpguy »

3.5 x 39 Viton. I have extras. PM me for price.
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Re: Exhaust O-Ring Size

Post by KDXGarage »

Make sure the pipe is not bent, preventing a proper seal.
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Re: Exhaust O-Ring Size

Post by firsthere »

Pipe didn't leak until the original seals were replaced with after market. So far It hasn't had a dent in it (yet) though it could be a questionable fit after looking closely. I may try without the copper gasket to seat the flange further in. What do you think?

I picked up a couple sizes 39 & 40mm ID x 3mm. If those don't do the trick I will check back with you pumpguy.
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Re: Exhaust O-Ring Size

Post by pumpguy »

Your choices might be too small in cross section. My notes show a 3.5 mm cross section. Actual uncompressed cross section measures 0.132 inches.

My notes also show the Kawasaki OEM O ring for the exhaust is # 670E3039. List price was $9.70 each.
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Re: Exhaust O-Ring Size

Post by bufftester »

Don't run it without the copper gasket, the pipe and the cylinder will take turns battering each other to match themselves. The copper is malleable and is there for that reason. Like Pumpguy said, the aftermarket o-rings are likely too small. You can also use some hi-temp RTV to seal that joint
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Re: Exhaust O-Ring Size

Post by KDXGarage »

Not running the copper crush gasket is a HORRIBLE idea. How long do you want a steel pipe banging against an aluminum housing?

If the part number is 30 39, then it is 3.0 mm and 39 mm.

If it's not Viton, they won't last real long.


Did you buy the pipe new?

How old are the pipe springs?
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Re: Exhaust O-Ring Size

Post by kdxdazz »

The inside of my cylinder barrel was worn so I changed the second o ring to 4mm, as already said you can't not use the copper crush washer, it's there to seal the exhaust gases, the orings are there to hold the pipe in place, without the copper crush washer the hot exhaust gases will hit the orings and burn them out, once the pipes take a hit and bends, the exhaust barrel may no longer mate perfect with the cylinder, take off the orings and copper crush washer and dummy mount it and feel that the two surfaces are running parallel, if they are not just take off the exhaust and use a peice of pipe to tweak it, it really is an important part of 2 stroke exhaust maintenance
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Re: Exhaust O-Ring Size

Post by firsthere »

The pipe was bought new 2 years and the springs are OEM, 2004. The PC pipe sealed fine (along with an FMF Rev, and the stocker. Maybe I tweaked the PC pipe without denting it as the flang looks further out on the top. The difference between 3mm vs 3.5 cross section might be part of the problem as well, that's the size of the aftermarket ones.
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Re: Exhaust O-Ring Size

Post by firsthere »

Spent some time evaluating the situation and came up with this;

- The outer o ring was cooked and broke apart when picking it out. Inner looked ok. Strange as the exhaust passes the inner first.

- The copper crush washer was compressed within .001 all the way around with no sign of wear or abrasion. (I recall the stock pipe disintegrated the lower half of the original washer so this is a good indicator of misalignment.)

- Pipe fits flush to the washer with no silencer attached, in the proper position from what I can tell.

- Test fitting the Stock muffler wants to push the stinger down slightly. FMF turbine core wants to pull the stinger up- quite a bit. No sign of crash damage to either muffler.

Right now the best I can come up with is the silencer may be causing the header leak by mis-positioning the pipe. The problem is compounded by poor sealing of the aftermarket O-rings.

I'm open to ideas?
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Re: Exhaust O-Ring Size

Post by KDXGarage »

First, I would like to say you have really over-analyzed the hell out of it. Therefore, I could easily hang out with a like minded person. :partyman:

Great job on checking everything.

I would loosen ALL pipe and silencer / spark arrestor mounting brackets, buy new o-rings, copper crush gasket and springs, then slowly tighten all the mounting brackets a little on each one until all are fully tight, then see about how crooked it is.
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Re: Exhaust O-Ring Size

Post by bufftester »

Yeah, something sounds a bit tweaked if your silencer is pulling the whole thing out of alignment. Make sure your pipe mount brackets are all good and tight, the front lower one tends to tear in half. Then I would adjust the silencer mounting so it doesn't exert leverage on the pipe.
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Re: Exhaust O-Ring Size

Post by kdxdazz »

I had the same thing on my bike when I bought it, silencer pipe wouldn't line up, you have to tweak the header pipe, double check all the exhaust brackets are straight as if not that can affect the rotation of the pipe
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Re: Exhaust O-Ring Size

Post by KDXGarage »

Somehow, it just seems that loosening ALL the brackets for the pipe AND silencer / spark arrestor, THEN tightening them up little by little is required on many of my bikes.
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Re: Exhaust O-Ring Size

Post by doakley »

KDXGarage wrote: 07:32 pm Nov 07 2020 Somehow, it just seems that loosening ALL the brackets for the pipe AND silencer / spark arrestor, THEN tightening them up little by little is required on many of my bikes.
Agree with KDXG here. I think this is the only way you gain be sure everything is lined up properly. If it is really leaking badly, I would seriously consider adding a bead of hi temp RTV in there, maybe between the two O rings? :blink:
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Re: Exhaust O-Ring Size

Post by KDXGarage »

Also, make sure none of the pipe brackets are bent.
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Re: Exhaust O-Ring Size

Post by firsthere »

Well after several trials, I finally manage to stop the header from leaking. Root cause, tweaked pipe (even though no dents). Straightened it out using a section of wooden closet pole inserted in the header. I found the PC Platnium II exhaust are pretty light duty as they bend with just moderate effort. I suspect a log crossing may have bottomed on the pipe leaving no dent just re-contouring the pipe. Bolting up the stock silencer and using it as a gauge helped perfect the proper alignment.
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Re: Exhaust O-Ring Size

Post by KDXGarage »

Cool. Thanks for the follow up.
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Re: Exhaust O-Ring Size

Post by JZ05220r »

pumpguy wrote: 02:36 pm Nov 01 2020 3.5 x 39 Viton. I have extras. PM me for price.
I know this is an old post but I am looking to find some oversized o rings for my pipe. Not sure if 39 mm is the inner or out diameter. Thanks
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Re: Exhaust O-Ring Size

Post by KDXGarage »

ID

670E3039

https://www.partzilla.com/product/kawas ... 5e2703db09

$14.75 retail each. That's too much for me!

Make sure your cylinder is not worn from coming into contact with the steel pipe. If the pipe bangs against the aluminum cylinder, it will widen the diameter, causing a loose fit. 35 years ago, we had Moto Seal, a white putty. I guess a glob of RTV will do it, too.

Also, check your spring tension and copper crush gasket. (and yet again, pipe not being bent and misaligned)
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