My over the winter project was to add, or try to add, 4 to 5 horse power to my 2003 CRF150F. I am pleased to say the project is finally completed! I added the following performance parts. Price of each in [ ] at the end. Bore / hone. [$50] JE Piston and rings, 12.5 to 1, with the dome milled down to make it 11.5 to 1. The .050 over piston makes the displacement 159.6 cc's to run in a class with max displacement of 160cc. [$180] Ported the head. I didn't really make the ports larger, I just cleaned out the casting flaws and lines, and matched the intake manifold to the port. [$50 for the Dremel tool] 28mm Mikuni flat slide carb (TM28). This was a bear to get jetted, but after countless hours of trial and error, I finally got it. [$120, used] Powroll performance camshaft. This cam has just a little lift, but quite a bit of duration, just what I wanted for the high rpm / high speeds of flat track racing. [$150] Powroll Thrust Nozzle exhaust. [$30] Various required gaskets and o-rings. [$50] Total cost, $630. Would be about $700+ with a new carb. But was it worth it? I believe it was. This little bike really came alive. Yesterday, after getting the jetting problem ironed out, I took it out onto a 1/4 mile oval short track to see what she'd do. I was running at about half throttle for a few laps, just to get things warmed up. My nephew pulled up along side me on his stock CRF150. We looked at each other and smiled. We boh twisted the throttles open at the same time, and by the time we reached the next turn 70 or 80 yards down the straight, I was at least five bike lengths ahead of him. After the next straight, I was 10 to 15 bike lengths ahead. What makes it better is that I weight 165 pounds, to his 100 pounds. So my little 150 really came alive with those $630 worth of mods. I then let my Nephew ride my bike, heck, I had a hard time getting him off of it. He was turning lap times 3 seconds faster on my bike as he was his, and a second faster then I was, probably because he weighs 60 pounds less then me. (I sure ain't going to admit he's a better rider then I am, even though he is). So ... if you have an extra 6-700 dollars, and enjoy making slow bikes go faster, I would suggest giving it a try. Next on the list. Powroll oversized header pipe, and maybe, just maybe, mods to the CDI box (incorrectly called the rev box). If I can make or have someone make a CDI box that keeps the RPM below 10,000 but still have the advantage of the better ignition curve, I'm going to give it a try. If there are any after market ignition companies reading this that can make a CDI box do what I want, send me one, I'll test it out for you.