Header to mid-pipe exhaust gap?

Put on a FMF header and can... After some fussing, I'm still left with this gap - it's a couple mm max. On startup and a quick poodle around the block, I didn't detect a leak.

Is this okay to leave? Or is it guaranteed to cause more issues? I might be able to use some spacers at the mounts to get them perfectly straight, I guess? Just wondering if I'm being over meticulous / anal? :)




That's looks a little bigger than I am used to seeing, or would like to see. Any chance one of them got tweaked?

That's why they say to slather it with silicone... Is your subframe tweaked? Did you tighten everything from back to front?

Edited by dirtydrew

Thanks for the feedback, guys. I went out and fiddled more tonight to have the bike ready for next weekend. I stuck a couple washers between the frame and mid-pipe, and loosened / tightened the header (not in that order). The gap is definitely smaller and acceptable, now.

In theory, nothing should be tweaked... I did have the bike in pieces, so adjusting the subframe a mm could be a great idea and have a big impact... I haven't done the high temp silicone, yet, because the clearances seem great. If things warm up, expand, and start to let air out, that will definitely be my next attack, too...

As a side note, if anybody ever needs to "clean" fork seals and doesn't have the usual forum recommended materials, iPad / cell phone screen protectors work a treat! Cut to shape like a little scoop and dig that grit out! :D

FMF pipes suck, they never fit very well, every bike i've ever seen with an FMF pipe is always leaking at the exhaust joint, even if it fits ok when it is new, it will loosen up and leak over time.


I'm probably going to get flamed over this, but that's been my experience.


My buddy had a TI megabomb on his 250, the header is trashed, it is flimsy and has tons of dents from minor hits with rocks. He went back to stock and has nailed a bunch of rocks and hasn't dented his header since.


Same thing with an FMF fatty on a CR125 I had, it tweaked almost immediately from minor crashes

I agree with you on the FMF Ti headers, I think if you look at it you dent it. But they're as light as air and serve the purpose well.

I agree with you on the FMF Ti headers, I think if you look at it you dent it. But they're as light as air and serve the purpose well.


Except that the vast majority of people who buy these headers could use a trip to the gym and a few less cheeseburgers.

I could use a trip to the gym, myself! Or a hundred...

The header looks like its for the CRF250X, R and X headers have slightly different bends which could explain the problem you have if your mid pipe or header was designed for a CRF250X

There are differences in the Mid Pipe mounting point on the sub frame as well between model years as well as X and R models.

Double check that all the parts are correct for your bike year and model.

If all good you could take your mid pipe and header to a car exhaust shop and have them either reduce the mid pipe end or expand the header pipe end to close up the gap for a tighter fit.

Hi temp silicone will only last so long if the gap is so big, eventually the engine vibrations will rattle the join loose if you don't tighten up that gap.

Edited by Van Wick

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