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mega CRF250

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I ride a TUF 250 and these bikes really rock when the engine is modified properly for performance and it doesn't hurt reliability, either!!! More fun to ride than my stock 450, that's for sure!

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Jesse builds a good engine package our company TUF competes with his product in pro arenacross .One of the most recent engines based on the 2012 has produced a solid 45.5 HP run thats corrected to sae standards and it maintained 45 hp past 12000 rpm the ability to maintain hp comes from volumetric eficeincy in other words our cylinder head and cam combination works very well as there is less time to fill the cylinder @ very high rpms our dyno graphs show this as we maintained over 44 hp fromm 11500 to 13000 rpm.I have showed a coulpe diferent dyno graphs of the same run just show the difference in corection factors which can show completely different numbers but they cant change the curve which shows how long the engine pulls and is some times a better indicator of engine performance.Maintaining hp in the over rev is huge on

Image (109).jpg

Image (110).jpga 250 .

the engine graphed here has oem valves our spring kit and cam, a wiseco piston the measured compression ratio ended up 13.5-1 with shaping of the piston.we used renegade sx4+ fuel and a off the shelf FMF pipe .

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Ron its good to see a competior giving credit to another - i admire that. i have only heard good also about TUF racing, I have used Jesse a few times and always found value and performance. our KXF250 he has just done just rips.

good man.

mark.

Jesse builds a good engine package our company TUF competes with his product in pro arenacross .One of the most recent engines based on the 2012 has produced a solid 45.5 HP run thats corrected to sae standards and it maintained 45 hp past 12000 rpm the ability to maintain hp comes from volumetric eficeincy in other words our cylinder head and cam combination works very well as there is less time to fill the cylinder @ very high rpms our dyno graphs show this as we maintained over 44 hp fromm 11500 to 13000 rpm.I have showed a coulpe diferent dyno graphs of the same run just show the difference in corection factors which can show completely different numbers but they cant change the curve which shows how long the engine pulls and is some times a better indicator of engine performance.Maintaining hp in the over rev is huge on

[ATTACH]17293[/ATTACH]

[ATTACH]17294[/ATTACH]a 250 .

the engine graphed here has oem valves our spring kit and cam, a wiseco piston the measured compression ratio ended up 13.5-1 with shaping of the piston.we used renegade sx4+ fuel and a off the shelf FMF pipe .

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Hard to compare Ron and Jesse as they have 2 totally different dynos. Rons measures off the rear wheel, Jesse's off the counter shaft.

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if he measures of the crank then the hp will b less by the time it puts it to the ground.still good hp for a 250f.

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JEESES motors are fast period .Varner told me today he dynoed a crf 250 on his dyno this was one from moto concepts and it made 44 hp .the only details i know are it was a cosworth head and a procircut cam.i have heard of engines running over 15-1 compression to get to those numbers.I thought i would be over 46 hp this week but not there yet 2 least on my dyno some pepole in the uk were reporting 46 hp with our past heads and cams.I have recently found a break through that added up 2.5 hp it was a huge change in the curve.FMF is sending me some custom exhaust parts made to my specifications im hoping to find some thing there .\Im sure that an old school can thats to loud would put me over that number.

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RH:

Any advantage running run race fuels without an ECU remap?

Stock Cam, Valves, FMF RCT+Megabomb and higher compression piston?

the renegade fuel even with out remapping will add some peak and a nice gain both sides of the peak hp .

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JEESES motors are fast period .Varner told me today he dynoed a crf 250 on his dyno this was one from moto concepts and it made 44 hp .the only details i know are it was a cosworth head and a procircut cam.i have heard of engines running over 15-1 compression to get to those numbers.I thought i would be over 46 hp this week but not there yet 2 least on my dyno some pepole in the uk were reporting 46 hp with our past heads and cams.I have recently found a break through that added up 2.5 hp it was a huge change in the curve.FMF is sending me some custom exhaust parts made to my specifications im hoping to find some thing there .\Im sure that an old school can thats to loud would put me over that number.

HI Ron

By any chance would that be Terry Varner..

Chet

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HI Ron

By any chance would that be Terry Varner..

Chet

you got it Terry and i have been freinds since around 2004 i spent a week @ his house when he lived in corona i built some special motors for the KTMs .it seems when there looking for that tiny little extra they keep using me .using me up that is .

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Ron, whats the reliabity with these engines, say a hourly time frame? Im 210, Expert HS racer and like the idea of a 250f but im just too much for a stock 250f. Curious to know how long a RH engine (as an example) is going to last? Im taking into account that a regular maintence schedule is applied.

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you got it Terry and i have been freinds since around 2004 i spent a week @ his house when he lived in corona i built some special motors for the KTMs .it seems when there looking for that tiny little extra they keep using me .using me up that is .

Ron

I figured it was Terry Varner, I met him at Loretta Lynn's ATV pro race back in 87, he was porting 2 stroke cylinders there in the back of a van, seen alot of cylinders with the Varner name engraved on them. I was also into 2 stroke porting at the time also, Tom Carlson was there too from TC racing, I hear he is still building engines too.

Chet

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Thanks for the tip on Renegade fuel. With the higher octane, can you dial in more spark advance to get a more complete fuel burn without detonation?

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Ron , I can purchase that package from tuf ? I have a pro circuit Ti 4R system on the bike already, will that package work with that system?

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one of our customers in the uk uses cosworth pistons with our cam and head there claiming 45 hp with pump fuel and thats what they race with i beleive there using the yosh pipe also

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