I have an FMF MegaMax on my Wolverine. Last week, on a ride, one of the mounting bolts rattled off and the slip on came off the headpipe a bit. That made a really loud noise! A quick trailside fix and I was back in business. this weekend, pulled off the slip on to clean it up and install new mounting bolts with locktite. When I had everything buttoned up, I checked for leaks. I'm getting a little leak right by the area where the slip on meets the headpipe. I had picked up and OEM gasket that goes between the two, but that doesn't fit with the FMF on there.

So those of you with aftermarket setups, what's the best way to get a nice tight seal between the headpipe and the slip on?

 

The fmf slip-ons are notoriously bad for leaking at the joint in the middle. I'm not sure about yours, but my megamax 2 that I had on my recon didn't even have any kind of clamp on it. What I did was push the exhaust as far forward on the mounting bolts as it can go and then re-tighten them so there's pressure at the slip-on joint. If that doesn't do the trick, I would probably try some kind of high temperature liquid gasket maker. You'll have to find something that is at least semi-flexible when cured though, because the usual furnace cement that you can use on car exhausts would break up and rattle right out of the quad exhaust.

 

Part of the problem is with the mounts lined up and bolted into place, there's still a bit of a gap between the headpipe and the silencer. It's almost there, but not quite all the way; a few of those slits in the slip are allowing the blow by. I'm thinking of cutting out a bit from an aluminum cat and using that to form the seal.

 

I tried using some flashing to create a gasket inside the slip on. The problem with that is the FMF slip on is flaired out just enough to clear the stock headpipe. Adding anything thicker than a strand of hair and it doesn't fit. I guess the only option is liquid gasket or header wrap. It's not a big deal, it only makes a minor ticking noise if you listen, but I just want it to be perfect.

 

High Temp RTV Silicone (looks orange in color). This is what I use on mine. Key thing for this is the prep work prior to application.

You'll need to clean both mating surfaces extremely well. that means using alcohol (or acetone) on the headpipe as well as the mating surface inside the midpipe (attached to the slipon). Let them dry thoroughly. Then apply with a super clean finger (no nose goblins) to both surfaces and let them set for about 10-15 minutes. Final step is to assemble. Tighten up your mounting hardware and then wipe off the excess with another goblin free finger. Let it set for a minimum of 24 hours.

This isn't a foolproof method, but it seals it up for a fairly long time. Said time depends on how stable your exhaust system is once all the hardware is tightened up. A good rule of thumb is that any bolt that has viberated out should be re-installed after cleaning both the bolt and the mating nut with carb cleaner and a dab (just a drop) of blue removable locktite.

 

The problem is, I'm only getting the leak out of the small slits cut into the mounting surface of the slip on. It's such a small hole, but it is leaking.

 

If there is a slit, then it's meant to have a clamp over it to tighten it down. Do the RTV thing and put the clamp on while the RTV is still wet - once dry, it'll likely seal up your leak.

If you need, I'll take a photo of a real clamp (one like I use) for your viewing pleasure. It will tighten down around the circumference of the pipe, and not just crush it in a couple of places like all the "muffler" clamps do. A band clamp is the only way to go - and you can't get the same clamping forces from a hose clamp.

 

Cool! A pic would be really helpful. I beleive I have a band clamp on there now, but if they make a wider one, I may want to go that route.

 

Here's a pic of what I'm dealing with. As you can see, it's a really small gap between the slip on and the head pipe. However, it was enough to cause a small black spot on the head pipe after my last ride.

Sorry for the blury pic:

Exhaust Leak

 

It looks to me like they need to be pushed together at least another 1/4 inch. If the silencer is as far forward as it will move on it's mounts, then maybe your headpipe needs to be bent back a hair. If the silencer fell of the mounts, then there's a good chance that it bent the headpipe crooked when it came loose.