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Cylinder works BIG BORE kits?

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Hey just wondering if anyone has any experience with this and if they are somthing to stay away from? They look very inviting on ebay and for the price....

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thumper racing uses a higher capacity cooling sleve than the other brands if heat is an issue.

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I built a couple of KX269F's within the last year.

A great upgrade for a 250F.

 

I don't know if I'd want to build a big bore 450 though.

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If you do go this route first off its going to wear you out faster and Def be a beast. Your gonna need to have the head ported for a bb application and get a high end cam, the stage three hot cam is designed for this but there's plenty of other options. If you don't do those two things then your gonna most likely be dissatisfied and it'll turn your stock all around set up into a low end straight tractor pulling motor that drops off early.

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Had a 05 with a Athena big bore kit , ran perfect , dropped a tooth on the rear, tons of holeshots stock cam, stock everything else. Adjusted fuel screw that's it. Felt like stock powerwise ,but you could ride a gear up everywhere versus stock bore.Porting the head,cam not a must,but more is always better. The early Athena pistons would crack on the top of the piston ,pumping oil in the air box. Big bore is a very easy to ride motor.

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Yeah im running a JE high compression piston right now with a yoshimura cam and the head was professionally ported also rs4 yoshimura exhaust . I love the power but when it comes time to rebuild it i was thinking of trying one out. Just wasnt sure if its somthing to stay away from.

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i rode a thumper racing true 500 cc kit on an 07 CRF 450 a few years ago.  it was much easer to ride than stock.  when i twisted the throttle the bike just kept going and going, tons of managable power.

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I built a CRF511 for a guy. 100mm big bore with the 3mm stroker crank. It was/is "come to Jesus" fast. I ported the head too because I was worried about it running out of air on the top end. It doesn't run out of air, put it that way. :smirk:

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Sounds awesome but with theses newer fuel injection bike like mine. Im not sure what changes i would have to make? Or is it as easy as just having it returned? It sounds like most of these bikes have been carberated that you guys speak of.

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Sounds awesome but with theses newer fuel injection bike like mine. Im not sure what changes i would have to make? Or is it as easy as just having it returned? It sounds like most of these bikes have been carberated that you guys speak of.

 

the Kawi's I built were FI.

No mapping was required. That is not to say they wouldn't have been better with some knowledgeable mapping.

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Awesome well thanks for the info guys once it comes time ill probably go that route and ill keep u guys posted

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i recall Travis talking about including a re-map with his kits but you would have to check with him to make sure.  with carb bikes you have to re-jet, so i would expect it with the FI bikes as well (reprograming).

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I'm going to throw this out there simply because I don't understand it but, my 450 has more power than I know what to do with.  I've been riding bikes, sled's, and 4 wheelers all my life and my 450 is absolutely enough power what is the purpose of a big bore bike.

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I'm going to throw this out there simply because I don't understand it but, my 450 has more power than I know what to do with. I've been riding bikes, sled's, and 4 wheelers all my life and my 450 is absolutely enough power what is the purpose of a big bore bike.

for people that are riding on the limits on the 450

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I'm going to throw this out there simply because I don't understand it but, my 450 has more power than I know what to do with.  I've been riding bikes, sled's, and 4 wheelers all my life and my 450 is absolutely enough power what is the purpose of a big bore bike.

ya, i have the same opinon.  i have found that even though i cannot use all the stock 450 power the BB bikes are easer to ride.  your not finding yourself holding it all the way open on those uphills or out of corners.  so the meat of the power on BB bikes is everywhere, not just middle or top.  kinda hard to explain but if you get the chance to ride one check it out for yourself.

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