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02 cylinder base machining

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Okay so everyone always talks about the cylinder base macining the 05-07 cr250's...has anybody else done it on the 02-04 cr's? And if so how did it turn out?

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If you google Eric Gorr you will see that he wrote about doing the mod on a 2003 CR250. I have an '03 and he actually did the mod for me but since I'm using an '05-'07 base gasket my base was only machined .02" to compensate the difference.

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The article was talking about the 03 having a powervalve redesign then goes on to say for the widest powerband on 02-04 to machine the base down 0.030. Conrad how we're your results after good I assume?

Edited by rippah

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I just got an 03 cr250 and out of curiosity I did a search for 03 cr250 eric gorr on google and found the following link.  All of the guys in this thread really liked the "mo betta" porting that Eric Gorr did on their 03's which included shaving the base, cutting the head for either pump premium or race fuel, doing some transfer work and opening up the exhaust port.

 

http://dirtrider.net/forums3/threads/03-cr250-motor-mods-eric-gorr-10-21-02.64372/

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i did it to one of our CR'S.  02 cut 0.030 off the bottom bored to 265 and a bit of epoxy work in the transfer runners. you will have to bolt the cylinder down do a soldier  squish test on the head and then get it cut to the right cc & squish . i had mine done to run non E super. Have Ron at RB Designs in portland do the head.

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My '03 runs awesome! I also had some porting done but didn't ask for a specific blue print , just told EG my skill level and the type of riding I do. Before purchasing my CR I was in the market for a 2012 KTM 250sx so I was sorta using the sx specs as a guideline in setting up my CR which is why I automatically went with a 50 tooth rear sprocket. The set up worked alright in stock form but after the rebuild I feel that its a little too much bottom and can easily go down to a 49 possibly 48. But iron man sprockets aren't cheap so it's difficult for me to experiment w different gear set ups.

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This is why I love this site, good knowledgable people helping others out great info thanks guys!!

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the has a much broader power band now. it still has a transitional hit into the mid, but not so explosive. it has usable & controllable  torque on the bottom with an assertive transition into the mid and still pulls on top pretty good. it runs very clean in low throttle  positions.

I set it up with 

boysen rad valve

keihen 38 air striker

FMF Gnarly pipe

and make to adjust the the power valve cables.

 

Now the modded 2001 motor in an 02 frame that i'm selling in the classifieds(honda cr 265) is a 265 as well with much less removed from the bottom of the cylinder and not nearly as much epoxy work in the transfer ports. same pipe,carb and reed block, much different running motor.

 

The 01 make more torque right off idle and pulls harder right thru the mid without as much of a mid hit. You can lug and ride a gear high and it wont stall.

 

My son rides the 02 and likes it better. we ride single track and he is A-AA rider, so he likes the assertive mid pull on the RC power valve motor.

 

I like the 01. it runs more like a KTM 300.  I've had KTM 250/300 xc's so i have something to compare to.

 

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