I've had an FMF Q4 on my WR250X for about a year and today I put the stock muffler back on. It turned out to be a major undertaking.

First of all, FMF's aluminum step-down collar had to be removed with a Dremel cut-off wheel, after removing the header. It wouldn't come off with a steel drift and hammer.

Second, I had to re-install the EXUP cables and adjust them according to the fuel injection diagnostic procedure (#53) in the service manual. It's interesting that either 1) revving the engine in neutral doesn't open the EXUP valve, or 2) the EXUP valve opens at very high RPM, to which I'm unwilling to rev in neutral.

Doing all this required removal of seat, side panels, tank shrouds, and tank. It took hours. I changed the spark plug while I had the tank off.

Next week I should be able to report on any power and rideability differences. I have a PCIII with a custom tune, so it will be interesting.

Cool did you start it up? Was there a big difference in your mind?

The EXUP valve doesn't move more-and-more according to engine rpm like they did back in the olden daze.
Some people (like me and lots of people over on the Yamaha FZ-1 Owner's Association) think they're there to reduce noise out the muffler as much as anything. :)

2strokeYardSale said:

I think you mean it doesn't CLOSE. The EXUP is sprung normally in the open position. When it moves, it is closing the valve, not opening it.

Check out this thread. The video at the bottom of the page shows it doesn't move all that much under light loads. Too bad MTB didn't rev it higher in that vid so we could see it move to the extreme.

2strokeYardSale said:

Next time (a little late, and maybe you won't have to do it again, but....) throw it in the freezer or deep freeze if you have one. That little sleeve will fall right off.:thumbsup:

I wanted to take a vid of the EXUP at the track, but luckily I didn't...

Today I fell on the right side instead of the usual left fall :lol:

First impression on having EXUP back during tracking:

1. I swift more often... I guess it was because I "feel" that the bike had a little bit more bottom end. and therefore I didn't have to keep the rev up all the time.. which, is a good thing I guess

2. The bike was more twitchy at low speed turns (hair pins to be exact)

After I got the EXUP back, I only tracked ONCE at the usual track, so the impression might not be accurate... EXUP... KIV first :ride:

mwakey said:

I rode it 13 miles today, surface streets, mostly 40-50 mph limit, with a short 65 mph freeway blast. I rode as usual, getting into top gear ASAP, generally pulling from lower RPMs with higher gears.

There is no noticeable power loss from the Q4. I think there is more mid-range power, most noticeable rolling on from 50 mph indicated in fifth gear. It pulled cleanly in sixth from as low as 33 mph, same as before.

So I think all the extra torque my bike makes comes from the airbox flapper and PCIII map.

Bravo for testing it & proving with your 33 MPH speed response it is at least close or better than piped. A timed roll on would have been good too but if you "feel" it is better mid mission accomplished. Mid is where it is at on this style bike. Quiet just makes it even better.

If you can dial the map leaner till you find surging at eack value in throttle settings, then dial it back up a notch you can probably make it better. I've always gone to the "lean" end of jetting as it is easier to find that fine line IMO. Fat has a wider band to try to narrow down.

It's too bad you didn't have your bike and someone else's that had the setup you had, to have a fair comparison. Some got blamed for that 'feel' being 'in your mind' not too long ago. Getting on one bike and trying it out, then to jump on another one right after would have been a great way to see what does what. Interesting...

Why would I need another bike? How would a different bike be a more fair comparison than the same bike? I've been riding it 3-5 days a week for a year in that state of tune. I swapped mufflers over the weekend and continued riding Monday. Same route, same speeds, same throttle.

More commute miles since my previous post. It definately does not make less power anywhere. It still lugs up the 45 mph hill at 50 indicated in sixth gear. It still lugs up the 40 mph hill at 46 indicated in sixth. Getting on the freeway I wound it out to merge ahead of a semi-truck; no change in the top end. It may seem faster because I'm more likely to shift later because it doesn't make noise when revved, compared to the Q4.

I'll repeat: the stock muffler does not make a noticeable difference in power than the Q4 anywhere in the powerband, with the PCIII dyno-tuned for the Q4.

2strokeYardSale said:

Not wanting to argue with you about the rest of what you said, since I have not tried this. But it seems to me that no matter what mods you have, this bike is going to lug in 6th gear at those speeds. Why are you in 6th at such a low speed?


edit: It occurs to me that some might have different gears which makes 6th more useable at those speeds. For me with stock gearing on the X 6th gear is something that only gets used above 60 MPH.

mwakey said:

Same reason the rest of us are..............................it doesn't have a 7th gear.;)

Time to switch to hi range. :D

[quote name='SheWolf']It's too bad you didn't have your bike and someone else's that had the setup you had, to have a fair comparison. Some got blamed for that 'feel' being 'in your mind' not too long ago.

The big factor in his favor is he is not being influenced by the increased sound distorting his perspective. A well known & documented phenomonon.

Seems he has specific speed references he can dial the bike to and as I suspected, the pipe is of little consequence. I've seen it with 250f, 450f MX bikes & a variety of enduros & multi cylinder streetbikes. A timed 1/8 or 1/4, even roll on times would be nice but if he finds it just as quick, or even better in the mid while stealthy & reliable, free from packing concerns or trail damage, all the better. :thumbsup:

Proper "jetting" and the tune of airbox & backpressure play roles that interface with cams & intake tract length that just "hogging out" airboxes & opening up exhaust flow, more often than not, decrease the true usable power curve of an engine for street and/or trail.

It is good to read someone went beyond the hype & "fact" and tried it for themselves, not all are sheep it seems. Well done.

I had to do it. I took a stock bike (with the exception of a tuner, which was set at stock for this and a 12T CS) out and rode it around for a bit, just to see how it felt. Brought it back to the parking lot and then jumped on mine (after I had set the FI mapping back to stock ;) ). Did the exact same things. Went thru the gears, went from a low lug 30 in 4th and gave it gas (same as on the stocker) and from what I experienced the pickup was a lot slower with the stock bike than with mine. Then went and did a straight away rip on a 1/4 mile stretch of road. His stock bike was almost 2 seconds slower than mine at the end. *shrugs* He tried it himself and agreed that mine felt more 'awake' and responsive.

I've got a friend with a bike setup almost exactly like mine. The only difference is he has a full FMF pipe and I don't. Other than that, they are pretty much identical. Same air box mods, same FI tuner, same gearing, etc, etc.

Doing a roll-on on pavement, his is markedly faster. Riding one and jumping on another won't tell you squat. Run them side-by-side and you'll see the difference a pipe can make.

Am I going to run out and buy a Q4? Eh, probably not . . . but that doesn't mean it wouldn't make a difference. It does.

2strokeYardSale said:

And people are wondering why they only get 50-55 mpg... Your bike will not last long with this kind of abuse.

As for the topic, if you feel you're getting better response out of the stock can then by all means use it.

As for pipes giving your more output, my friend who recently bought a DRZ-400, 2009 (not the same bike but same principle. dyno'ed his BONE STOCK 400 at 32, after putting a P4 and power core on he tried it again, 35.

Really, it comes down to personal preference, you think the stock pipe is better use it, I'll be getting a Q4 when i buy my next bike.

Krabill said:

Yeah it will.

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When I said it lugs up hills, I meant it chugs up at low RPM. Poor choice of words. If I get the engine to the point of actually lugging, I shift it. My bike has a lot more low-RPM torque than it did when stock, but still has stock gearing, and I use sixth down to around 40 mph.

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Oh really? Gradual acceleration from the bottom of the powerband is abuse? I've only got 6500 mi on it; how much longer before it breaks?

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Re-read the post and follow-up: Not better, same. Same performance, different weight, different maintenance, different passenger accomodation. All things to consider for the prospective purchaser.

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Exactly!

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Irrelevant. Different bikes respond to different mods. My friend who recently bought a turbo for his Busa....


Pretty interesting how I started an informational thread about the mechanical pitfalls of swapping a Q4 back to stock and people come out of the woodwork to defend aftermarket pipes.

No such things as identicle bikes. My bikes were always faster than identicle bike because a) I was lighter and weight afffects bike greatly b) My dad was a bad ass mechanic. Proper tuning is HUGE. Pipe changes require tuning differences. The aftermarket pipe is meant to open the door to more HP(with proper tuning) not just slap it on. I'll take the best tuned bike either way, but if the best tuned bike also has a GOOD aftermarket pipe that the winner.