need more top-end in my 99 CR125....Mr. Gorr???

[XtremeAir125]

Ok, here's the deal. My bike falls flat on it's face when it hits into the high rpm range, I bought Eric Gorr's Motocross Guide and it really helps me a lot. I also have a YZ125 that I love but those Yamaha parts are expensive!! Anyway, my bike has a FMF Fatty Pipe w/PowercoreII Silencer, and RAD Valve w/Carbon Fiber Reeds. I read in his book to get more top-end you should add "exhaust valve plugs" made by Boyesen Performance, but I emailed Boyesen and they don't make them :think ?? The plugs are made to be installed in place of the HPP valves. The plugs are installed in place of the HPP valves. The exhaust port height can be raised to 28 millimeters measured from the top of the cylinder. That will really make the engine rev. And it says, by removing the exhaust valves you can also remove the powervalve governor that drives off the crankshaft. That serves to reduce drag and friction on the crank and yield an extra horsepower. Can Eric do all that work for me? I know my gearing doesn't have much do to with it really but I have a 51 tooth rear sprocket, would a 50 help more? Also, a 90-96 CR250 carb would also benefit, I'm currently looking around for one. I'm probably going to get it ported with the "Mo-better Everywhere" style, and possible a 133cc over the winter. Would a 95 cylinder head be worth it too to throw in? I just wanna get this bike as fast as I can. Thanks guys!

 

[XtremeAir125]

ok guys, 26 posts and still no answer.....come on help me out please? thanks!

 

[marcusgunby]

The exhaust plugs and no govenor is for cart use-you really loose out on bottom end doing this mod.I would go for the 38mm carb and 133kit.

 

[EricGorr]

The exhaust plugs are sold by Wes Gilbert of Boyesen Performance Porting in New Tripoli PA. We use that set-up for dirt track and shifter karts, and some expert level mx racers. Its makes the engine too pipey and difficult to ride off-road. I wouldn't suggest that mod.
Good luck

 

[XtremeAir125]

marcus- i just bought a PJ 38mm off a 94 CR250, i'll try it out this spring, what about the 144 instead of the 133? my bike is a 99 CR125

 

[marcusgunby]

The 144 is a bit more midrange and bottom although it can rev well if modified for top end.If you love to rev, a 133 will be better IMO.If you like a mini 250 feel the 144 may be better.