2002 wr426 13-13.5:1


4 replies to this topic
  • shelbyguy

Posted December 12, 2010 - 09:58 AM

#1

anyone getting away with this kind of compression on pump gas?

im far more framiliar with cars than bikes atm....

my understanding compression goes up, timing becomes an issue (detonation)
anyone running 13 or even 13.5:1 on 91-92octane?


motors apart looking for big bore upgrades, and or stroker assemblies as the motor developed a rod knock with the PO.


thanks in advance

  • dgcars

Posted December 12, 2010 - 10:01 AM

#2

anyone getting away with this kind of compression on pump gas?

im far more framiliar with cars than bikes atm....

my understanding compression goes up, timing becomes an issue (detonation)
anyone running 13 or even 13.5:1 on 91-92octane?


motors apart looking for big bore upgrades, and or stroker assemblies as the motor developed a rod knock with the PO.


thanks in advance


This why God made a 'big bore kit' on the 7th day...he was a biker too...:thumbsup:

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  • shelbyguy

Posted December 12, 2010 - 10:18 AM

#3

This why God made a 'big bore kit' on the 7th day...he was a biker too...:thumbsup:


i truly like this idea honestly.

but here's the thing, it has a standard bore weisco piston that he said developed more noise after the piston.

im thinking BIG bore, and send crank to mr.crank, replace ti-valves with stainless, clean up the ports a bit, then clean out the frame best as possible.

whats bout the "norm" for big bore's?

ive seen 444, 465, 477

stock bore is 94mm correct?

where do i go from here. speak to me wr gawds.

je? weisco?

i plan on keeping the bike for in town blasts, its in supermoto trim at the moment and get some dirt items for next fall, winter.

  • shelbyguy

Posted December 27, 2010 - 07:54 PM

#4

bump?

  • Birdy426

Posted December 28, 2010 - 11:07 AM

#5

Forged pistons ARE noisy. They run a bit looser in the bore. Just the nature of the beast. I've used Wiseco with good results on my 426 (now 444), and JE on my son's 250 (now 310). As far as big bore sizes, 444 is the norm for a 426. That's as big as you can take the bore. I have read posts about stroking the crank to get to 478, but I have not been able to find anyone other than CrankWorks that said they could do it...and they wanted an arm, leg and left nut (custom work, ya know).

I run pump premium (91 octane here in cali) on both my 444 and the boy's 310 with 13.5:1 compression and no problems. We've even run mid-grade (89 octane) without issue on occasion when that's all that was available. Had to add octane booster to keep the rattles away when using 87 octane pump regular. We have added oversize radiators and Boyeson supercoolers to both bikes "just in case", but had no issues prior to that...




 
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