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Discussion Starter · #1 ·
for any of you yfz 450 owners that want more power, B & B Racing now has a 475cc stroker kit available.
depending on elevation and exhaust setup, this kit should net you between 55-60 hp to the wheels. it will be a little less the higher in elevation you go of course.
we will disassemble your motor,stroke the crank, bore and replate your cylinder, port and flow your head, put in our custom 12.8:1 compression piston. then reassemble with all new gaskets.
the torque increase you'll get will far exceed the hp gains. but it is torque that accelarates you not hp.
you ship us your motor, and in 6-8 weeks it will be shipped back complete ready to bolt in and go.of course you will need to rejet, and i will be able to give you jetting requirements at that time.
the entire package shipped back to you complete is $2025.
have any questions feel free to ask. just don't ask me what the dimensions are, those are a trade secret. and we don't wish for any of our competition to get ahold of them. we are the first and the best performance engine builders to offer a motor kit for the yfz. our kits are built for reliability and to kick ass.
and the motor will look bone stock from the outside so you'll never have to tell your friends what they just got smoked by.
 

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that must be a very small stroke increase since even a plus 2mm bore will yield 458cc's and a +3 that Selector was talking about will get to 468 and those are with the stock stroke.

sounds really expensive for a few ponies ... I personally would never buy something from a company that would not release the engine specs. cylinder wall thickness on a motor like the YFZ is very important
 

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Discussion Starter · #4 ·
ok, heres a spec, you can only safely go to 97mm bore on the yfz and yz cylinders. so that is what i'm using, a 97 mm bore.
it's not the HP you're getting from this kit it's the torque. more torque equals much faster accelaration.
you can go over 97 mm on the bore, but you lose the reliability. why do you think so many raptor owners have problems with reliability on thier 727 and biugger motors?
how many engine builders put a one year warranty on thier motors? :nono
 

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ok .... I had to bust out the TI-85 graphing calculator for this one, but if its a 97mm bore than the stroke is 64.2 mm or an increase of 2.2 mm over the stock 62 mm

convert the mm to cm ....

bore x bore x stroke x .7854 = cc's

9.7 x 9.7 x X x .7854 = 475 cubic centimers

X = 6.42 or 64.2 mm stroke

but im guessing you guys are rounding up and are really building a +2 mm stroke

9.7 x 9.7 x 6.4 x .7854 = 473cc's
 
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