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250 4 stroke hp

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i just finished dynoing a kx250 f with my porting and web cams 14-1 compresion fmf pipe and u4 fuel we were only able to get 35.5 hp from the bike but almost 19.5 pounds of torque with the location of the intake port im not able to get any way near as good flow as the crf head im 6 hp better with the crf 250s on a bad day .with a larger carb and a better pipe i can see a possible 3 hp gain on the kaw but thats still only 38.5 hp it makes me wonder what the procircut bikes are really making i have heard from a good source that there @ 42 hp right where im curently @ with the crfs .i dynoed a 06 450 yamaha and dialed it in and got 46.6 hp it went to another dyno and got 49.4 hp i just got a supermoto rag that listed all the 450s on the joker machine dyno and they were all around 3 hp better than what i have seen .The crf 250s that i have been building have made the mains in the out door nationals i also watched one of them run against the 450s @ a local race and put 40 secounds on secound place the 250 was the only bike making a short run up hill double it was interesting also that the 250 was getting good hole shots on a up hill start secound to third in the corner every time .the 450s would jump the 250 off the corner about 2 bike lenghts because of there torque but the 250 would real them back in on the straights and just wait untill a corner with a berm and rail around them and when clear the rider would just start pulling away .i beleive that the 250 with 42 hp peak will go down the fast sections of track with the 450s because of less wheel spin if we could some how get 24 pounds of torque from a 250 to make it come away from the corners better i think it would be the ultimate weapon .

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i just finished dynoing a kx250 f with my porting and web cams 14-1 compresion fmf pipe and u4 fuel we were only able to get 35.5 hp from the bike but almost 19.5 pounds of torque with the location of the intake port im not able to get any way near as good flow as the crf head im 6 hp better with the crf 250s on a bad day .with a larger carb and a better pipe i can see a possible 3 hp gain on the kaw but thats still only 38.5 hp it makes me wonder what the procircut bikes are really making i have heard from a good source that there @ 42 hp right where im curently @ with the crfs .i dynoed a 06 450 yamaha and dialed it in and got 46.6 hp it went to another dyno and got 49.4 hp i just got a supermoto rag that listed all the 450s on the joker machine dyno and they were all around 3 hp better than what i have seen .The crf 250s that i have been building have made the mains in the out door nationals i also watched one of them run against the 450s @ a local race and put 40 secounds on secound place the 250 was the only bike making a short run up hill double it was interesting also that the 250 was getting good hole shots on a up hill start secound to third in the corner every time .the 450s would jump the 250 off the corner about 2 bike lenghts because of there torque but the 250 would real them back in on the straights and just wait untill a corner with a berm and rail around them and when clear the rider would just start pulling away .i beleive that the 250 with 42 hp peak will go down the fast sections of track with the 450s because of less wheel spin if we could some how get 24 pounds of torque from a 250 to make it come away from the corners better i think it would be the ultimate weapon .
what exactly do you do to get 42 out of the crf?

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a special cam 14.5-1 piston exstensive port and flow testing chm pipe sm1 u4 fuel mr9 will pull another hp changes in ignition timing

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Hy RHC,

how much hp and torque have you got from crf 250 ? what do you make to it ?

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Hy RHC,

how much hp and torque have you got from crf 250 ? what do you make to it ?

so close to 42 that you might as well call it that and over 21 pounds of torque the power stays over 40 for a 2000 rpm spread.

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over 21 pounds of torque and 40 hp to a 2000 rpm spread is awesome!!!

How do you have made it ? what camshaft and springs (...crankshaft and bearing..too) do you have set in ? .....and head's work ?

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so close to 42 that you might as well call it that and over 21 pounds of torque the power stays over 40 for a 2000 rpm spread.

yes sir Ron, that little head you did for us with the 14.5 je and your cam on our ponca crf sure worked great ,

our rider was eating the other hondas and the yamahas and what little kawis were there were just slow compared to the little honda :thumbsup:

i just fell in love with the little thing , it was pulling two teeth taller gearing and just ripping it up doing it ,

i did not want to give that bike back to the dad :applause: ,

i am going to try and get it back so i can freshen it up after ponca just so i can cheet and take it to my favorite track and kill the 450's on the straights ,---the guys just thing its a big motor :ride::applause:

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So basically your dyno is reading under,are we safe to say that the worked crf250 from you may be pushing a little more than 42 RWHP? Then again the other dyno's could be reading over. :thumbsup: Ron, I have been meaning to ask you this,have you anything gone on with the YZ250F's?.To be honest, I just thought you were dedicated to the CRF's.

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over 21 pounds of torque and 40 hp to a 2000 rpm spread is awesome!!!

How do you have made it ? what camshaft and springs (...crankshaft and bearing..too) do you have set in ? .....and head's work ?

i have my own cams and springs we are using stock crank shafts .I have freinds in Italy Zanzani i redesighned the motobi cylinder heads for there vintage race bikes i think they are making over 40 hp now with a 250 .making 40 hp with a 250 cc race engine is not any thing new we were making 38 hp on the old ducati 2 valve singles 10 years ago also the motobis, these little bikes on a road race course and full road race fairings will hit top speeds of 130 mph.

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Hey RHC I'm italian man, who's Zanzani ? where can I try him ?

Thanks

creed 75

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I guess you do not have anything gone on with Yami's. :thumbsup:

yes Ron will do the yamahas also---i have a special set of cams that web grinds with a special set of springs along with a one off piston with head work , some very careful crank work and balancing ,

with real fuel and a vortex ignition and these little yamahas will run 42 to 43 hp with 20 ft lbs of torque ---

i had one of these yamahas at the track the same day i also had the crf that i built( they were both fresh) that had all of Ron's stuff in it ,

and i gota say that the crf ran harder than the yamaha ,----they both were very good ---but the honda had an advantage with low end torque and better pull off the corner ----

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Thanks for the comeback kelstr! I am interested in a set of cams and a piston,I do my own porting work. 42 -43 sounds perfect for a 250. :thumbsup:The only thing is, I want to stay with the Yami springs and valves.

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What mod is doing the most in that power-up? Or maybe it's working all together? :thumbsup:

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What mod is doing the most in that power-up? Or maybe it's working all together? :ride:

yes it all does work together , ---it took awhile to get it sorted out ,

you really want to run good fuel-----the mr9 is the best , but the u4 works good also,

if you have a good wiseco distributer and make him put the order in ( it is not shown in the catalouge at all)

wiseco number R803M07700---its called a 13.5 piston, but it goes in these 06's at right about 14 or better,--you must clay the motor --i have had to re-flycut the eyebrows deeper to get the .050 intake and .080 on the exhaust clearance you needed,

and you need to really watch the deck height on the piston it sits flush with the deck and the head gskt is only .033 after its tightened and the piston will just hit the head a 14,000 rpm --which is ok ----its just some of these o6's it was above the deck and i had to cut apart a new head gskt and add a piece to a stock gskt to make up the .010 or so i needed .---

and call web cam and get the 943 grind cams ----277 duration 356 lift ---degree them in at 104 lc intake and 108 exhaust,

get the vc-y26 spring kit and call mike tolle and order the vortex box and run map 3 and use the big gun race only pipe and there you go :thumbsup:

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.050" and .080" on the piston to valve clearance seems awfully generous, why so big?

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rhc what are your middle ground motors putting out? 42hp is great and all, but in all reality i dont need that much. i would like to push my 250 but to more of the safe side. why dont we call it modified instead of full race. I just dont think i could use all 42hp. i like where the stock power is on my 05 i just want some more.

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