I don't know how an exhaust pipe works.

[JimmyHoffa]

I've been working on engines for a long while, and have rebuilt one entire quad by myself, and done serious engine and transmission work on two dirt bikes and one motorcycle with great success. However, upon the installation of my FMF Hi-Flow header and Titanium 4 exhaust can, I was baffled. (no pun intended)

The can slides on to a midpipe, and two strategically placed exhaust springs hold the can to the midpipe. There is a serious air leak at this joint. Both parts were made by FMF and are in good shape, but I'm definitely confused by the weird blow-by exhaust gases. I was under the impression that air leaks were bad. If anybody has this issue (or non issue??) let me know what you think.

[underpowered]

air leaks are bad, could could possible hurt performance slightly. i would put a little Ultra copper high temp silicone on the joint to seal it up.

[idro]

Exhaust leak past your header won't hurt your atv's performance. When you see performance loss from exhaust leak is on a car, that is because of the 02 sensors. Your ecu is backing off on timing etc to compensate.

[nevadanotch]

I have a Pro Aluminum exhaust pipe on my 400EX with the same type of setup. The spring loaded slip joint on this pipe and many other pipes with this design are designed to allow a small amount of movement between the can and mid pipe. Exhaust gas leaking past this slip joint is perfectly normal. Do not try to seal the joint with any kind of sealant. If you are getting an excessive amount of exhaust gas blow by at the slip joint, then you probably have an alignment problem between the can and the mid pipe. Check to make sure your mid pipe is positioned properly so that the mid pipe aligns with the can. In other words, the mid pipe should be parallel to the can at the joint where they fit together.

[interceptorz28]

maybe its the springs. are they brand new?

[troutman561]

My FMF came with a metal exhaust gasket to go btwn the can and the head pipe...Could be you didnt get it or overlooked it during installation..

[JimmyHoffa]

Okay. I actually had a leak at the head, but I knew that was actually a real problem and I didn't say anything about it. I fixed that, and there's no leak until the midpipe hits the can. I tightened up my spring ends and it seems to have lessened a little bit. The midpipe and the can are definitely parallel. (I had to weld the screen core to the inlet cap, and I took extra care to make sure stuff was square.) There's no room for any type of gasket other than liquid gasket, which would last about one lap. I'm pretty sure I've decided to ignore it. Thanks!

[BossmanEX]

Put a hose clamp around it and clamp it down tight. My HMF leaked like that and the hose clamp worked fine for me.

[joshyz125]

Originally posted by troutman561
My FMF came with a metal exhaust gasket to go btwn the can and the head pipe...Could be you didnt get it or overlooked it during installation..

Was yours a slipon?

My Yosh didn't have any gaskets, just a very tight fit, and i couldn't hear any leaks, but if you looks real close at the pipe at the joints, you would see little black marks that you could tell exhaust was coming through.

I would not put any silicone on it.

[krt400ex]

its fine...unless there is alot of it leaking...but a little is normal.

[JimmyHoffa]

I think I got it dialed in. I tapped around the fitting with a piece of wood to shrink it up a bit, and now it fits pretty tightly. I got the jetting dialed in too, and I definitely got lots of power with this setup.