I got this as a Christmas present, it added plenty of power to my crf 150r and installing it wasn't that hard. If it broke which it hasn't after 2 years, I would defiantly buy it again.
FMF Factory 4.1 Slip-On Exhaust
- 28 Reviews
- 37 Questions
The FMF Factory 4.1 slip-on exhaust is the same exhaust that professional racers use to bring home championships around the world. FMF constructed the Factory 4.1 slip-on exhaust to offer the lightest weight slip-on on the market. The technology in this slip-on exhaust cannot be found in any other exhaust. The proprietary Chamber Core technology allows for smoother and more efficient exhaust flow to maximize the power output. Since the Factory 4.1 slip-on exhaust is meant to be used for competition, FMF made this pipe ready to take to the track straight out of the box. The FMF Factory 4.1 has been designed to allow for easy maintenance with a removable sleeve for repacking and it offers the ability to fine tune the performance of the exhaust with the addition of tuning inserts and the option of a spark arrestor to give you no boundaries.
- The lightest system available.
- Boosts low-mid torque and offers a broader powerband with more over-rev.
- Patented Chamber Core for optimum performance.
- Engineered for compactness and centralized mass for improved handling.
- Exclusive mounting design.
- Easily serviced for re-packing.
- Slip-on mufflers are available with a titanium or stainless steel midpipe.
- Customizable with performance tuning inserts and spark arrestor module.
- Meets AMA sound requirements on most models.
Note: For closed course competition use only. Not intended for street use.
I like the exhaust and power bomb header a lot! The only problem I had with this was installing it. It was a huge pain in the you know what. You have to buy your own clamps to secure the power bomb header to your exhaust. You also need to buy high temp silicone. This costs about $30, and you also have to let it sit for 24 hours for the best outcome. Other than that it took me about 30 minutes to take the old exhaust off and put the new one on. Hope this helps to future customers.
Love this pipe! Was easy to install, sounds great, and excellent power increase. (I also installed a power bomb)
the fmf slip-on exhaust is the best exhaust out there i put it on my raptor 350 and it is amazing.the bike has a noticeable increase in speed horsepower and torque.the pipe has a very deep sound to it without the spark arrester and with the spark arrester it is very quiet.Thank you motorsport team for the great advice of the pipe and evrything else.
I put this pipe on my sons outlaw and it is outstanding. 10 minutes to install and it sounds like a hoard of bees , may be loud for some but I like it Haha neihbors don't but who cares. the power is instantly noyicable.only one pet peeve , when not on the gas it has a peculiar whistle which makes it sound like something is loose and rattling on it.highly recommend if you don't mind loud
I installed the Factory 4.1 on a very strong running 07 Honda CRF450R and what a huge improvement. Combined with a FMF Mega Bomb header this thing is a beast. installation was a simple 15 minute task, the fit is perfect. Awesome product.
If you are looking for an exhaust, this slip on application is a great addition to your bike. I installed it on my 06 YZ450F. Would buy another one in a heart beat if need be. Installation was a breeze with the slip on, the blue anodized finish is TRICK, and the muffler is holding up really well after numerous rides.
RIDER BEWARE!!!!! This is a louder pipe designed for closed course riding. If your riding area is stringent on decibel ratings, think about some of FMF's quieter mufflers such as the new Q4. The new ones look much better than the ones I saw when shopping for mufflers and believe me, they will not get you tickets that end your ride!
Paired this up with the Megabomb header. Night and day difference! Hit much faster than stock and noticeable mid range increase. Used this set up on 2011 YZ450F
This product combined with the power bomb header completely got rid of the throttle snap bog on my 2007 crf250r. Added tons of power on bottom and mid, would recommend to anyone lookin to get rid of the stock duals
i had just sold my go kart and used the money i had earned to buy this and the megabomb header...i would say that is not necessarily worth the 600 dollars only because im not a pro rider i am sust starting to race. but it dafinately helped my CRF 150R in the manner of my 2nd gear holeshot, it kickes butt now...
I have been running another brand of pipes on both of my CRF250Rs for just over a year now. I put a power bomb header with a 4.1 muffler on my '09 and WOW what a difference. Not only did it lower the sound, but the power increase was very real from bottom to top.
I put this slip on exhaust on my 2005 Yamaha YFZ 450. It went on without any problems. FMF also gave a larger main jet with this exhaust. I contacted FMF and they said the larger jet should keep the air fuel mixture correct but if it is not perfect to turn the air/fuel screw located on the bottom of the carb out a half turn. I put the jet in but did not mess with the air/fuel screw and my atv runs great. There is a big difference with this slip on exhaust and I recommend it to everyone.
Great product...low to mid range gains
I just got this pipe and the powerbomb header for my 2012 yfz 450r replacing the corked-up stock pipe, and saw amazing improvments from bottom to top end. all around great product. oh and incase you were wondering like i was, no fuel optimizer is needed.
Noticeable power increase on my '09 YZF 250 looks and sounds sick. My next purchase will be the megabomb header, to go with it
I like it it added lots of power I was riding on the road and went to full throttle for a race takeoff and my tires just got to spinning. Very good buy check my bike out on Facebook. scar ray is my name on there
Decent exhaust in all categories but in my opinion has a major design flaw when put on a CRF250X.
When trying to lift the bike onto the stand or move the bike around in the back of the truck, there just isn't enough room between the fender and the exhaust to use the traditional grab spot under the rear fender without burning your hand from the much too close exhaust.
It could also be a major problem if you're a woods rider, like me, and ever have to try to lift the rear end out of a mud hole after getting stuck.
I've never encountered this problem on any other bike / exhaust combo I've ever had. The stock Honda muffler doesn't have this problem.
Needless to say, I'm pretty disappointed in my purchase and wish I could return in.
Bought for 06 crf250r, already had the fmf megabomb on bike, fit good the only complaint i have is the tire (stock size) rubs the exhaust when suspension is compressed. makes good power and sound with the 94Db insert
This was easy to install. Noticed power out of the turns right away. I was always a factory replacement guy no aftermarket parts, I'm very happy with this product.
easy to install and great power
looks great on my 09 yfz450r
i put this on along with the mega bomb header the pair made the bike feel like a whole new animal