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big bore kit
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Posted by: zeke83

anyone know where you can get a 450 kit for the yfz that does not take alot of other mods, like the cam and valves?

Posted by: YFZCHAMP

Yoshimura, baldwin, alba (email Kory Ellis, he can help you If you like), Can say what mods are needed for each kit but they do exist. Also consider a strokerkit instead, or a slaved head, ported motor for more power, none of those need cam mods

Posted by: SRH

quote:
Originally posted by zeke83
anyone know where you can get a 450 kit for the yfz that does not take alot of other mods, like the cam and valves?

hey, go to www.yfzcentral.com and go to the forums get ahold of bob from magnolia tractor i think his name is bansheebc, he was selling 450 kits for 500 bucks, comes with crank , piston and all that to bump the yfz up to a 450 and wakes it up quite alot from what i hear, you wanna go with 470s and 480s and stuff it starts to strain the mmotor and cuts down on the reliability, cams and valves only come into play with higher compression motors, youll still notice gains without porting, cams , bigger valves etc besides i dont think for the money youd spend you could justify doing bigger valves porting and all that

Posted by: gasboot

before you make the decision to add the 450 crank decide whether you want to ride your quad or look at it! i had sparks 470 kit then went back to 450 after cracked cylinder dont know how this will do but wish i stuck with other mods like valves,port & polish, carbs maybe cam etc. just my thoughts~ all you get is holeshots

Posted by: SRH

quote:
Originally posted by gasboot
before you make the decision to add the 450 crank decide whether you want to ride your quad or look at it! i had sparks 470 kit then went back to 450 after cracked cylinder dont know how this will do but wish i stuck with other mods like valves,port & polish, carbs maybe cam etc. just my thoughts~ all you get is holeshots

how do you get 470ccs out of a 450 kit? cylinder modifications? maybe thats what caused the cylinder to crack, like i said alot of guys run the 450 kits and i havent heard of any problems whether there is or not i dunno

Posted by: gasboot

quote:
Originally posted by SRH
how do you get 470ccs out of a 450 kit? cylinder modifications? maybe thats what caused the cylinder to crack, like i said alot of guys run the 450 kits and i havent heard of any problems whether there is or not i dunno

i cracked the cylinder so i had to get new everything cylinder, piston, rod so i went to a 450 cylinder or maybe the crank makes it a 450 either way found out you can do better things to your motor than go to the 450 the stroke is too tall i hear

Posted by: YFZCHAMP

Two of the top YFZ450 racers out here had thier pistons fracture because to cylinder mods. My motor has a stock bore and simple add ons. My friend has a ported and polished MX motor and the gains are nice AND reliable and not really that costly. Before I did any mods to my motor, ASK yourself what do I want on the other side of this project, duning, MX, GNCC, desert racing, then spend your money as desired. Call up the top motor shops in the country, most have a tech to asnswer any questions you have, and some guarrantee thier work...

Posted by: PurePerformance

For MX, I wouldnt bore the cylinder. Id rather go with the WR Crank and Piston. Id also recommend to do the Sparks Oiling Mod.

Posted by: YFZCHAMP

PP makes a good suggestion, best of luck

Posted by: PurePerformance

I forgot to add that the WR kit adds more torque as which boring the cylinder is more of a top end advantage.

www.velocityracingatv.com Contact Nils, he can get his hands on any motor mod.

Posted by: SRH

quote:
Originally posted by PurePerformance
I forgot to add that the WR kit adds more torque as which boring the cylinder is more of a top end advantage.

www.velocityracingatv.com Contact Nils, he can get his hands on any motor mod.

the wr kit is the one i was talking about, i rode a yz 450f today and that had so much more power than my yfz, i dunno if its where it was so light or what

Posted by: ketchup

That's because the dirtbike comes from the factory with much more HP than the quad.

Posted by: YFZCHAMP

TRUE, the power to weight ratio is much higher. They tried the WR motor in the quad, It flopped (burnt up) So what Yammmie did was take the bottom end from the WR and the top from the YZ450F and married they up, botta bing, YFZ450 motor with the torque of the WR and the rev of the YZ. Also HP does not always mean better, ridibility and control are more important

Posted by: 03dynasty

What do you mean they took the bottom end from the WR?

Posted by: YFZCHAMP

the design for the lower part, the bottom end, the crank, the gears ect were all based on but no the same as the wr450f, look it up yourself, it's common knowledge.

Posted by: EX 80

whats so different about the WR and YZ top ends?

Posted by: YFZCHAMP

Well, for starters the compression is different, the piston is shorter, the cam is different, the porting is different, it is totally different on the yz, the YZ is intended to rev and race, the WR450f is intended to be a cruiser or desert bike, not an mx racer, for exact spec differences consult Yamaha. But the gears and grunt are better on th WR