Last year I had my WR250X dyno'd at a local race shop using their DynoJet dyno. First they did a base run with no modifications, then they installed the following parts...
• Delta Barrel 4 Exhaust System
• K&N Hi Flow Filter
• FMF EFI Power Programmer
As you can see from the graphic above, the stock bike had a peak horsepower of around 28.73 (at just under 9,000 rpm) and a peak torque of around 17.95 (at around 8000 rpm). With the new exhaust, FMF programmer, and K&N Filter, the bike ended up with a peak horsepower of 30.75 (at just over 9,000 rpm) and peak torque of 18.79 (at just over 8000 rpm). Overall, the modifications added just over 2 hp and just under 1 lb-ft of torque (compared to a stock WR250X). This might not sound like much, but for a 250 it's not bad.
With the new mods, the bike runs great. When the bike was stock, I noticed a dead spot early in the powerband... the bike just seemed to hesitate at low RPM's before starting to accelerare. That is now gone and it accelerates from a stop much better. The powerband seems to be a little smother overall as well. I'm real happy with the end result.
