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crf 250

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well i have made some small break troughs im @ just over 42 hp i have improved the curve considerably .i found that the engine configuration likes u2 better than u4 along with leaner jetting the trans likes motor oil better than atf the chm sm1 likes to be shorter on the can .the 07 ignition box doesnt do any thing for it it was suposed to raise the limiter and i cant see a diferen this engine looks as if it will keep arrying the power and i wont knoe untill i get a dferent box mr 9 made it loose power i think mxro1 will pop me up some more i will try to get the dyno sheet on line.

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So, I heard from a reliable source that does some work for Pro Circuit that Langston's bike does make :thumbsup: 44 HP but ONLY on the PC dyno. When they put the motor on other dyno's it produces 42 HP. Same motor, same setup...

Hmmm.....

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So, I heard from a reliable source that does some work for Pro Circuit that Langston's bike does make :thumbsup: 44 HP but ONLY on the PC dyno. When they put the motor on other dyno's it produces 42 HP. Same motor, same setup...

Hmmm.....

That sounds logical to me... 42 hp out of these 250f's is incredible. Great work RHC!

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Depending on the day and the dyno 34-35HP.

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the last bike i tested had just over 32 hp im going toget an 07 on here to see what it makes the modifyed kawasakis only make around 36 hp on my dyno with good fuel the best yamaha i had was 38 hp.nether one of the other brands heads flow even close to what these honda heads do.

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if always wanted to no that. do any of u no the top speed of one of these beasts?

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the last bike i tested had just over 32 hp im going toget an 07 on here to see what it makes the modifyed kawasakis only make around 36 hp on my dyno with good fuel the best yamaha i had was 38 hp.nether one of the other brands heads flow even close to what these honda heads do.

Whats your take on head flow vs. velocity?

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So your saying u2 is producing better numbers than u4? Thats kinda interesting. Is this only for this new setup or could it be used with others?

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Whats your take on head flow vs. velocity?

are you asking about calculated velocity determined by port cross section b/s and piston speed or measured velocity done with a pito tube on the flow bench .i have found that on single cylinder engines that calculated velocites in the 375 fps range work out for the best power curves .measured velocitys range between 325 and 350 @ the port 28 " h2o and try to keep the velocitys under 380 fps @ the apex of the ports ssr. filling in a port with epoxy with out measuring and keeping constant cross sections and measuring velocitys is a waist of time .

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So your saying u2 is producing better numbers than u4? Thats kinda interesting. Is this only for this new setup or could it be used with others?

this paticular engine combination wants more octane my first clue was when it made less hp with mr9 than the u4 .the power loss was so high in the curve i didnt think detonation could ocur but it makes more power with u2 i even tryed cutting the u2 with u4 it likes the u2 straight up the next fuel test will be with mxro1 a higher octane version of mr9 it could possibly make 1 more hp with this fuel. im not a fuel chemist im just using the trial and BANG method.

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this paticular engine combination wants more octane my first clue was when it made less hp with mr9 than the u4 .the power loss was so high in the curve i didnt think detonation could ocur but it makes more power with u2 i even tryed cutting the u2 with u4 it likes the u2 straight up the next fuel test will be with mxro1 a higher octane version of mr9 it could possibly make 1 more hp with this fuel. im not a fuel chemist im just using the trial and BANG method.

boy you gotta love the old trial and bang -----the only way to go !! :thumbsup:

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RHC

What jetting changes did you make between the U2/U4 and the MR9?

The MR9 is tad low on octane but the High end point may have something to do with it also. I have tried the MRPRO4 and it was not worth the cash by any means.

Junior has run U2 alot in our CRf and finds the response to be very good, using the seat of the pants test.... :thumbsup:

Mrx01 has curve much like U2 and U4 being mid way on octane. MRX01 does not like humidity and high temps from what I can recall.

Good luck, keep us posted..

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Which engine setup is this? Your normal ported head, custom web cam and piston Or is this something new? When you say engine oil do you mean 10w-40 or equivalent? This is exactly the type of info i need. it makes life so much easier when searching for the right combination.

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its a fully flow tested head i dont think theres a bunch of advantage there yet it does have a special cam though .im using good old mobil 1 synthetic 10w30 or 40.the next head will be with larger buckets for a cam with more duration yet in the .200" and .300 inch lift range the cam that im using now has about 8 more degress than the 192 i sell and is slightly off the bucket the advantages so far are not any more peak but the same peak as the 192 but for a longer spread and the same torque it does not start rolling over @ 13000 rpm i think it may carry over to 14000 .the cam im working on should raise the peak a little more and carry for sure to 14000 i think alot of the problem with raising the peak is to much intake length i should no tonight with a new experiment .

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Well i just did some more dyno test with the air box removed and a velocity stack instaled on the carb and nailed 42.4 hp right @ 13000 rpm and still on a upward slope it looks as if it could make 44 hp @ 14000 rpm so with some modifications to the air box it would be possible correction factor today is 1.00

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