Q4 Install Questions

OK, I know these are probably stupid simple questions but I need some help. I purchased a Q4 muffler off of sleezebay last week and it came in the post today. I was told ahead of time that the muffler didn't have the quiet insert or a spark arrestor so I ordered a replacement part from RMATV. Tonight I unwrapped the pkg (original packing with correct part # for FMF Q4 for 2004 CFR 250X) and mounted it up on the bike. It fit the bolt holes with no issues however I seem to have some minor trivial problems so I'm pleading out for some knowledge:

Muffler mounted on the bike with stock X header/mid pipe.


Replacement FMF spark arrestor/quiet insert for the Q4:


First Problem:

#1.) The Muffler pipe is a larger diameter than the stock mid-pipe by about 1/4-3/8". Can I just use high temp silicone tape to close the gap? Should I get a replacement stock mid-pipe gasket however doing this will close the partially but not 100%. Also, because the FMF pipe is larger than the stock muffler pipe I am not able to reuse the stock mid-pipe clamp. Does FMF make a clamp for this or what am I suppose to do here to clamp the exhaust to the stock mid-pipe/header?


Second Problem:

#2.) For the sake of typing it out, when I refer to the "spark arrestor" I'm referring to the combo FMF part which is a spark arrestor & quiet insert (1-pc). Installing the new spark arrestor in the end of the muffler (in the cone section) is a super tight fit. I cannot push it completely in by hand. In fact to get it in (I think this might work) I'd have to spray it with some high temp silicone spray and then I could probably tap it in with a mallot or something however I know I'd never be able to get it out again if I had to. Anyone else ever replaced the insert? How did it fit? Issues?

W/O Insert installed:


Looking down inside of the muffler:


Trying to fit the insert/spark arrestor (tight fit!!)



#3) Would anyone recommend replacing the stock header/mid pipe with a FMF part? If so, which one? I would hate to lose bottom end power.

#4) Rejetting: I have the air box mod and o-ring mod already done. Running #40/135 jets and the clip is currently in the #4 position. I'm at sea-level. Do I need to rejet? If so, to what?

I have owned several Q's and never seen one that the SA/quiet core was removable, I believe those are only used on their other models such as the Powercore4, Factory4.1, etc. The picture of the inside of your Q looks exactly like every one that I have ever seen.

As for sealing the headpipe to the midpipe you will need to use the OEM Honda gasket but I can't remember if the Q comes with a reducer that is inserted into the midpipe so that it will be tight around the gasket.High temp silicone will not work to fill that large of a gap, it will blow out. Most aftermarket pipes do not use any clamps between the headpipe and the midpipe.

If you like the bottom end from the stock headpipe then I don't think I would switch to an aftermarket unit.

So is the picture of the inside of the exhaust the spark arrestor built in? The insert spark arrestor is a very fine mesh especially when compared to the grillage inside the muffler.

There is a set screw at the tip of the cone (inside the pipe) where something could be installed.

Can someone post a pic of their Q4 looking at the end of the pipe and inside? Thanks.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now