Aftermarket Muffler with EXUP? - Updated: FMF Q4 with EXUP

I have a new universal FMF Q4 that's been sitting around the garage for a while. This is the same Q4 muffler many of you have, just without the pre-made pipe for connecting it to the header. I would likely start with pipe chopped from a stock muffler and fabricating the remaining portion. This would provide a clean junction to the header and attachment to the frame. I use the bike for sanctioned dual sport events/turkey runs here in the NJ/PA/NY area (aka tight woods, sand and rocks) so quiet and low end torque would be nice to maintain.

So here are my questions: Considering my type of use and having the choice, would you leave or remove the EXUP valve? It would simply be a matter of how much of the stock pipe I reuse so the EXUP could potentially stay. Has anyone done an aftermarket muffler and kept the EXUP before? Obviously removing it saves some weight and complexity but would keeping it improve bottom end and reduce noise?
Thanks

A member by the screen name of MTB did this.

He cut out a section of a full after-market system and welded in the EXUP crap from the stock pipe.

Not sure if he ever visits here any more or not. Been quite a while since I've seen him post.


I'd say the effort isn't worth the results, but then again if you have a ton of time and the ability to weld go for it.

Be sure to tell us what you think. And post pictures.




Edit to add: here's the thread <--- clicky

I would personally not go through the effort. the EXUP valve is there for two reasons, noise, and low end torque. Well, its a loved to be revved 250 thumper, so it does not have a lot of toque anyway...not down low. Opening it up with an aftermarket exhaust and adding a fuel programmer gets you some back.

And, FMF makes a perfect sleeve to mate their Q4 can up with the stock header, which is the set up I have.

I know you said you already have a universal can, just need the front pipe. I'd try to find one for the WRR, that had a damaged can, which you should be able ton get cheap, and you can mate the pipe from that to the can you have.

Well, I decided to tackle the idea. Considering the tight trails I ride, I prefer to not give up too much bottom end. I started by picking up a stock muffler for very cheap. I cut off the stock tailpipe at the muffler and removed the paint. the stock piping is stainless steel so it cleaned up well, matching the 304 SS tubing I had.



After mocking up the Universal Q4 and the newly liberated tailpipe to determine the amount of angle and length is needed to span the gap. I have the Q4 at a slightly higher angle than FMF's slipon. It better matches the lines of the bike and fortunately I have a DRC tail light with the 12 O'Clock board so turn signals won't get blasted by exhaust. Also, I have it tucked in tighter.

With this mock up, I cut some of the angle out of the 2" diameter inlet pipe that came with the Universal FMF Q4. This pipe has a slip fit into the Q4. Here you can see what the Universal Q4 (now discontinued) comes with.


The stock tail pipe is exactly 1.5" in diameter so it makes it easy to find tubing to match domestically here in the US. I got a 1.5"-to-2" 304 Stainless Steel transition to join the tailpipe to the remainder of the FMF pipe. I picked up some SS loops (seen in pic below) to use the FMF springs to secure the slip fit to the muffler.


After careful fit up of all the part on the bike, ensuring tight seams, I TIG welded the new tailpipe and fitted a new OEM mesh gasket for the header joint. The pic below shows the piping a bit darkened as I did ride with it shortly though I now need to get a PC to take advantage of it. Bike sounds and looks great. I happy that it is still reasonably quiet as that is a good way to preserve our dwindling trail access.

That a way! Nice job

Here is the finished product, mounted up on the bike. Since the front part of the midpipe is stock, there is no dent in it to clear the passenger foot peg bracket like the FMF off-the-shelf offering.


I removed the "Q4" sticker and aligned it to run parallel to the subframe for clean, tidy appearance. As a result, it is racked up a bit more than FMF's.


I like the result. It sounds great without being to loud. I need to get a tuner installed and dialed in prior to next season.

Awesome fab work it looks great.
Your pipe likely makes a touch more low to mid power than the off the shelf fmf and is quieter... it has next to nothing to do with the exup valve tho, the smaller dia pipe with a tiny baffle in it has that affect on power and noise, you can take the cables off the exup and you cant tell the difference.
The exup is open 99% of the time, it closes breifly in the mid range to make the bike quieter for some sound test yamaha needed to pass.
IMO there should be a offroad pipe offered for the wr250r made with smaller pipe and a smaller core in the silencer to boost low end more than the standard slipons do even tho they boost it some as is. 2 inch pipe and 2 inch silencer cores are for max top end on a 250, 1 3/4 or 1 5/8 inch would be better for low end and still rev good.