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YZ426F


stalteri
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During the research i have done on my WR426 I was thinking about going w/ the oversized and high comp piston... after all the research the big bore piston was worth it but the high comp piston wasnt worth it... If i remember right our current compression is 12.somehting:1 and the high comp pistons are 13.sumtin:1... the increased compression added more stress to the crank and crank bearings and you also had to re-shim the cylinder by adding a copper base gasket or something weird like that... it wasnt worth the time effort reduced durability of the engine and the increased cost of having to run race gas...

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During the research i have done on my WR426 I was thinking about going w/ the oversized and high comp piston... after all the research the big bore piston was worth it but the high comp piston wasnt worth it... If i remember right our current compression is 12.somehting:1 and the high comp pistons are 13.sumtin:1... the increased compression added more stress to the crank and crank bearings and you also had to re-shim the cylinder by adding a copper base gasket or something weird like that... it wasnt worth the time effort reduced durability of the engine and the increased cost of having to run race gas...

Yeah, thats what I'm trying to decide on. Max Power Inc has a 426 to 444 kit. Just don't know if its worth it?? :beerpint:

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12:1 is the regular compression for our motor.. and yes they still run on pump gas... allthough i mix my gas 50/50 half pump half race... i find i get a little cleaner throttle response outta it that way.. :D

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12:1 is the regular compression for our motor.. and yes they still run on pump gas... allthough i mix my gas 50/50 half pump half race... i find i get a little cleaner throttle response outta it that way.. :D

Do you use the VP U4 or the 76 100octane?

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I would go with the MaxPower 444cc kit.

A lot of people seem very happy with it. No complaints.

Check out the dynograph!

http://maxpower-engines.com/big-bore-kits/yz444f.htm

You know somebody that has this setup ONLY4STROKES? It sounds good to me (444cc) I talked to Will over there and he seems to know his stuff, i'm trying to see if I can get a better price from him but I doubt it. Are there any other brands out their or do you suggest this one?? Thanks

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Maxpower Engines does a REAL good job from what i hear... you might also want to try Kenz Cycle in Mesa, AZ as well... OR Eric Gorr at Foward Motion racing... both of those guys do good work as well.. the only problem with Gorr is he is a bit slow on his turn around time but does quality work..

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Read ME

Another GOOD thread

Between those 2 threads is where i have pretty much came up w/ my decision to not use the High Comp Piston.. :D

I'm gunna go with you on this one ISBB no high comp pistion for me, looks like the 444cc big bore is the best bet for increased performance with less aggrevation in the long run.... :D

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Hey ISBB, what do u think about a cam change with the big bore, is it necessary? I read some guys talking about it in those threads you sent out? :coocoo: Thanks for the help you have been very helpful we need to hookup for some :beerpint: and some :laughoff: ....

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Well i'm going for it (444cc), does anbody know the difference between Thumper racing and Maxpower?

Maxpower is about $100 bucks more than Thumper. I talked to Gary @ thumper he said they use the same parts that he knows of and dosent know why he is cheaper.. Has anybody used any of these guys or heard how good there work is? Thanks

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Stalteri920?? I was thinking about the cam change but if your comfortable w/ using the decomp lever like i am... All i planned on doin was the YZ time change on mine since its a wr i can rotate the cam one notch and get the same timing as you... its up to you... After watching brent and his buddy nick on thier new 450's kickin the crap outta em w/ the auto decomp and i fired up first kick it sorta changed my mind... The only thing you will gain is the autodecomp... so its just a preference thing... If you dont want to deal with the lever then do the cam swap... if you dont mind using the lever keep the same cam... BUT if you going to have it torn apart to send that stuff off i would suggest getting the head cleaned up a little w/ a little port job as well... since the thumpers make alot of power up top in the head..

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Stalteri920?? I was thinking about the cam change but if your comfortable w/ using the decomp lever like i am... All i planned on doin was the YZ time change on mine since its a wr i can rotate the cam one notch and get the same timing as you... its up to you... After watching brent and his buddy nick on thier new 450's kickin the crap outta em w/ the auto decomp and i fired up first kick it sorta changed my mind... The only thing you will gain is the autodecomp... so its just a preference thing... If you dont want to deal with the lever then do the cam swap... if you dont mind using the lever keep the same cam... BUT if you going to have it torn apart to send that stuff off i would suggest getting the head cleaned up a little w/ a little port job as well... since the thumpers make alot of power up top in the head..

Is there a place here in vegas that can do port job? I think I will leave the cam alone since i'm use to it now.

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i was goign to send my entire motor out to foward motion and do it... but i also hear there is a guy by the name of art who just built Sandy_YFZ's motor... and did a port job and the whole 9 yards... i have no idea how to get ahold of him but i hear he is a genious with engines..

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