FMF Racing Factory 4.1 RCT Titanium Anodized Full System
With the 2019 Yamaha YZ250F being almost all new this year, there were some engine changes that made a difference in how the little blue bike makes its power. Since the 2014 model introduction, it has been known for its incredible torque, but has been slightly looked down on for lack of top-end pulling power. For ‘19, the engineers at Yamaha took the “lack of top end” criticism to heart and made the YZ250F pull harder and longer than it ever has. But, you can’t make power everywhere. The newest version of the bike has given up a little bit of the bottom end torquey-ness it is known for. That's where the FMF Factory 4.1 Full System comes in.
FMF Factory 4.1 RCT Titanium Anodized Full System W/ Carbon End Cap Features:
- Available in Blue Anodized Titanium Muffler with Carbon End Cap
- New RTS (Rapid Tuning System)
- FMF uses the highest quality proprietary blend of alloy grade titanium made especially to our standards.
We didn’t have the pipe shipped out to us so I can’t talk about how it was packaged or how big or small the box was. That being said, in the past, FMF pipes always show up in a surprisingly small box with every part packaged individually to eliminate any metal-to-metal contact. Also, the system comes with a spark arrestor, though we tested without it installed.
Not that it is FMF’s fault at all, but bolting up a full system on a modern, reversed-cylinder YZ-F is a little tricky. Mainly, it’s just a pain in the behind to get to the header nuts since they are right in the center of the bike. But, the trick, at least that I found, was to change the order of operations and remove the left side upper engine mount. Instead of mounting the whole system up loosely, then going back and snugging up the bolts from the cylinder backward, you have to tighten the header nuts before putting on the muffler since it will be in the way of any wrench getting to the nuts. But that is universal for any YZ-F pipe, including stock. By removing the left upper engine mount, you are able to get to the header nuts with a 10mm wrench.
The couple things with the FMF pipe specifically are, rather than relatively loose fitting stock pipe junctions with cinch rings, the FMF junctions are much tighter fitting and don’t need the cinch rings. The plus side is that it saves weight, the downside is that it is a really good idea to throw some high temperature anti-seize lubricant (like copper grease) to both ease installation and make sure the pipes come apart if you plan on taking it off. Or if you don’t, you can skip this step. The other thing is that you have to pop out the rubber grommet and metal bushing from the stock muffler to mount up the FMF muffler. Not a big deal, it just adds a little time and finagling to the install.
Lastly, both systems were weighed off the bike on our office mail scale (not calibrated to NASA standards) but we can get a good idea of the difference. The stock YZ250F header and midpipe combo came in at 2.38 pounds (1,079 grams) and the muffler at 6.13 pounds (2,780 grams) for a total system weight of 8.51 pounds (3,859 grams). The FMF 4.1 header and midpipe is 1.23 pounds (560 grams) and the muffler is 4.96 pounds (2248 grams) for a total of 6.19 pounds - a total weight savings of 2.32 pounds, roughly.
On the track
With the bike in the stock standard map, I rode a few laps to see what the pipe can do. The first thing that I noticed is that the throttle response was about the same but the bike seemed to rev a little slower with the the FMF pipe. This can be good and bad depending on your riding style. Some testers felt that the stock YZ250F revved too quickly and they were shifting sooner than they would like. With that slightly slower revving engine, I did feel that there was more meat to the power down low and that we could leave it in a lower gear longer.
For jumps right out of tight inside corner, the extra grunt on the bottom was a welcomed improvement and didn’t require a stab of the clutch. The pipe didn’t effect mid-range and top-end as much as the bottom, but it did add just a small amount of extra grunt across the board. There is an audible change to the bike that switches from the stock sound that is slightly raspy, to a deeper, richer tone.
After riding it in the stock map, we used the Power Tuner app to load the Hard Hitting (Loamy) map to try and get back a little excitement and free revving feel. And it worked. The FMF Factory 4.1 pipe and the new map work awesome together. The Hard Hitting map brought back the quick revving, snappy power throughout the rpm, and the pipe seemed to increase the torque feeling.
We’ve had this pipe on for the majority of the 10 hours of alloted riding time we give each bike before the 250 shootout. Everything looks and sounds as good as new other than what looks to be some ink that has burned on right after the midpipe before the can, but that section is covered by the plastics anyway. A benefit of Yamaha’s reverse cylinder design is that the header is up high and very protected from impacts and front tire roost so there are no dings or scratches to speak of.
To be honest, I’ve been thinking that the Power Tuner app would make pipes a thing of the past, at least for YZ-Fs. In decades past, a full exhaust system on a dirt bike could really make a huge difference. But, with each passing year, stock exhaust pipes become better and better. Therefore, the gains from an aftermarket system has been shrinking - almost to the point that aftermarket pipes just move the power around, without making much more of it. But testing this FMF Factory 4.1 on the YZ250F has shown me that isn’t the case. A pipe and tunable ECU compliment each other rather than making each other obsolete.