APPLICATION: All four-strokes (tested here on 2009 Honda CRF450R)
PRICE: $349.99 (titanium); $299.99 (stainless steel)

WHAT IT IS: In addition to offering a full line of complete exhaust systems for four-stroke off-road motorcycles, FMF also has an equally as stacked line of slip-on mufflers, which are tuned to compliment a bike's stock header pipe. For the budget-conscious rider, or those looking to replace a damaged stock muffler, the Powercore Slip-On is just what the doctor ordered.
HITS: Installing the Powercore Slip-On took only a few minutes. In the '09 CRF450R, it was a matter or loosening and tightening four bolts. The muffler comes outfitted with a spark arrestor, but since we ride only on closed courses, we removed it before even firing up our test bike and haven’t tested the spark arrestor installed.
The first thing we noticed once we brought the EFI-equipped Honda to life was that the Powercore Slip-On gave the bike snappier throttle response. Not that the EFI Honda isn't snappy as delivered, mind you: the Powercore Slip-On just seems to wake the bike up even more down low. Out on the track, the system yields noticeable power gains down low and up top, as it allows the bike to pull further in each gear than it does with the OEM muffler installed. Having tested the complete FMF Factory 4.1 system with the Megabomb header, we must admit that the performance yielded by the cheaper $349.99 system is nearly every bit as good. Furthermore, the Powercore Slip-On works better than many full systems that we've tested this year.
MISSES: One of the days at the track was extremely muddy, as heavy rainfall in our area has left all of our tracks in sloppy condition lately. After a hard day's ride in the abrasive decomposed granite mud of Cahuilla Creek MX Park, we found that the FMF graphics on the muffler were practically worn off, Aesthetics aside, our only "performance" issue with the Powercore Slip-On was the louder-than-stock exhaust note. We didn't sound test it, but we're fairly certain that the system would not meet the 94 db requirement in AMA Pro Racing.
THE VERDICT: To be honest, there are very few riders who can make the most of the power that the '09 Honda CRF450R has to offer in bone stock condition. But that doesn't mean that we don't need more power!  Dollar for dollar, the FMF Powercore Slip-On is without a doubt the best aftermarket exhaust we've tested on the '09 Honda CRF450R.
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