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2007 KTM keeps blowing exhaust o-rings.

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Hello, I am having a problem with my 2007 250 XC (used for motocross) blowing pipe o-rings. I have searched online to no avail, and have inspected the flange for wear, and it looked ok. I feel as if it may be running hot, but jetting seems OK. For a while I have been noticing pipe bang after about 10 laps on a new set of o rings. When I take the pipe off, the o rings are rock hard, and both are broken on the left side. Using FMF o-rings that came with the pipe. Any ideas? I am stumped and would appreciate any input.

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My experience has been similar, so I use the exhaust o-rings and pucky it up with high temp copper manifold gasket maker.  Since doing this the bike never leaks splooge onto the frame and skidplate.  Every 15 hours I remove the pipe to inspect and clean it, and I do it all over again just for peace of mind.

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Thank you for your reply, I have been using RTV silicone (red) along with new o-rings, with no success. I will try to pick up the copper stuff next and see if I find an improvement. I feel like the bike is running a little too hot, but it seems as if my jetting is rich, but due to how hot it runs, I feel like my bike may be lean. I am currently running a 38 pilot jet, 165 main jet, with the JD low altitude needle, in 2nd position from bottom (just installed, did not notice a difference from stock needle in stock (2nd up) position. The bike does not seem to have much over rev, and seems as if the pilot circuit is spot on. When holding at around half throttle, the power and sound of the bike seems to "break-up", almost like a sputter, as if it were rich. I was thinking this was due to being to rich on the needle, but now might think I am too lean. Any ideas?

Edited by JRS7192

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You can buy better oversized viton o-rings. I have used these and they work well. I took this from a KTMtalk thread "3 x 45mm Viton o-rings from McMaster-Carr . Enter part #9263K318 into the product search box"

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check the plug? whats it look like?

I hace checked the plug, looks dark, with a bit of what looks like carbon on it... seems rich to me, but I am far from an expert...

I will look into these oversized viton o-rings.. I will also see if OEM ones work better. Thank you all for you input.

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Try fitting the pipe with muffler/silencer removed, just the springs attached and let the pipe find its 'natural' position. Then fit all the hangers and muffler to line up with the pipe. Even if it means spacing or leaving some off. This may mean tweaking the pipe a bit, but it's worth the effort. Nothing annoys me more than a leaky pipe!

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Try fitting the pipe with muffler/silencer removed, just the springs attached and let the pipe find its 'natural' position. Then fit all the hangers and muffler to line up with the pipe. Even if it means spacing or leaving some off. This may mean tweaking the pipe a bit, but it's worth the effort. Nothing annoys me more than a leaky pipe!

Thanks for your reply, I usually start with fitting it with springs alone, then work my way back, fitting silencer last. I will install new OEM rings and springs, and adjust the spring hangar so that the pipe sits dead center in flange, I will also try to bend any misaligned mounts... I will report back with the results after I ride this weekend.

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