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CRF250R / X Headpipe Sizes Powerband

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Hey guys.... looking for some info and help here....

but first i have to bore you with some blab.... dont want to break character, you know....

and...also... this is going to be biased towards michigan off road woods riding, since that is what i love the most for my own riding....

one of my personal favorite off road machines was a bike i had made for my wife... well, that's a lie.... i loved ALL of the machines i built for her.... it was sort of fun to have an excuse to setup another bike, all on the excuse of doing it for HER...some of you will know what i mean 👍

the XR200 turned fully setup XR212stroker was a fav with every guy at camp when she wasn't riding it....

the XR250 turned XR280 was like having a secret weapon in the woods (especially hopping off my ride then.. XR416).... the 280 was lighter, lower setup woods suspension... and oh my gawd, that finished 280 motor was sooooooo strong over such a wide powerband.... what a help and pleasure that was ...from the tight woods switchbacks, to the big woods and hills...!!

now... as good riding friends always do, they will happily flog and report on any machine you hand over to them....and all of ours rode the xr280 on both tame track, and wild trail.... lots of engine tune combinations....

and the ONE mod that completely sucked and EVERY rider gave a BIG THUMBS DOWN to....

was the: BIG TUBE HEADPIPE.....

every rider felt what the dyno showed..... power at the rev limiter was up about 1 HP... BUT everywhere from idle to the last 1000 rpm of the band was down...way down....

it felt like the powerband was kicked out at the knees....because it was....clutch abuse went from non-existant to mandatory.....you had to row the bike around the track with the shift lever....

so this is all about riding style and powerband focus.... smaller headpipes definately do create better velocity....suction...scavenging....throttle response... etc etc ...in the low to midrange rpm bands...

now...my current michigan off road ride is my favorite.... 2007 CRF250R turned 270R..... super light...dialed in suspension...incredible engine (threads on its development are somewhere here on TT)...

i had done all of my modding and dyno work with the stock exhaust in place...then got a great eBay deal on a Jardine dual exhaust...polished cans / carbon fiber caps....eye candy exhaust system.... BUT... it had a bigger than stock headpipe diameter...

Ron told me for my riding to ditch the big tube headpipe and just treat the jardine dual setup like a slip on....

the big tube headpipe did the same thing that the XR280 big tube did... killed bottom end and midrange response and lowered output all except for peakand overrev....and using the back of the jardine setup like an expensive slip on hooked to the stock headpipe yielded same bottom end and maybe .5 to .75 hp more power on top end.... but damn, it sure looks good...i am as big a sucker as anyone for trick looking parts...so the jardine high dollar slip on stays...lol

sooooo... i know i could do a search...but what fun would that be when i can bug everyone else??

did Honda have a smaller headpipe diameter on the crf250x model..??? i know they did on the 450x, since i had one ... does anyone have info on running one on a 250R model...??

i prefer the 250R weight.. and lighter / more nimble handling characteristics for woods riding..... and i may want to try out a smaller headpipe for tighter single track riding..

thanks in advance for any and all pipe info anyone can add

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John i had fmf make some smaller diameter head pipes for the 450 they added power below 4000 rpm you had to chug the motor on the dyno to see it it really did not afect the top end .on the standard bore 250 a pipe with .375" od seems to be the best i tryed a 1,5" and it hurt it every where.

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did Honda have a smaller headpipe diameter on the crf250x model..??? i know they did on the 450x, since i had one ... does anyone have info on running one on a 250R model...??

Yes the 250X has a smaller diameter headpipe than the 250R, it is also longer which should also aid low RPM torque. The bad news is that it will require some mods to work on the 06-09 model R's. Due to the dual pipes on those models,Honda moved the headpipe/midpipe juction forward of where it was located on the 04-05R's and the 04-09X's. What this means to you is that the X headpipe will end at a point too far rearward to mount to your midpipe. I believe that the X headpipe could be cut to the proper length as it appears to be straight at the point where the cut would be made. Next hurdle to clear would be the need for a bushing to increase the headpipe OD to match the midpipe ID, this could possibly be removed from the end of the X headpipe which was cut off, it was present which allowed the X headpipe to match the ID of the R midpipes.

You may want to view some X headpipes on eBay to get an idea of what I have described.

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well that seems to cover it all... thank you for that, Ron and Chopper..!

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Not sure if you were wanting to know or not, but the X head pipe OD is 1.375 until about the last 2 inches where the mid pipe connection is, at that point the OD increases to approx 1.490. But like what was already said the pipe wouldnt fit on a 07R without modifications.

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thanks so much for that! the R model headpipe is also 1.375" initially... just different length...

i wont mess with the X headpipe idea now...

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