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yammaxx

2012 YZ450 Big Bore?

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I bought the bike needing a piston and rings, and head gasket,  so instead of building back stock, I'm going  with a Athena big bore kit.  What size BB kit should I go with?  The bike is used for supermoto.  Anything else that needs to be upgraded in order to run the BB kit successfully?  The bike has less then a couple hours on it.  Thanks for the help.

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After doing a little more research, it looks like that Athena only offers a 102mm piston kit for the 2012 model.  Is that big of a piston going to be to heavy for a stock crank and bearings?  Will that cause premature wear to the crank and bearings?

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Well if you wanna do a big bore kit a new crank is suggested. You don't have to but are you sure the brand who makes the kit your cooking at is gonna suit you???

Yea, I have and Athena makes good BB Kits.  I had a Athena BB Kit on a DRZ that I built, and the bike had 8,000 miles on the kit when I sold it.  I have used Cylinder works kits as well on a few of the other DRZ's I have built in the past for people, their kits seem pretty good quality to.  What I want to avoid is having to replace crank, or causing the crank bearing to wear out faster because of a big piston flying around in there.  I know on a DRZ you can go to a 434 from a 400 and you don't see anymore wear on the crank  then a stock setup.  I'm just not a familiar with the 450f engine, so before I do something I regret, I want some opinions from guys that have actually done a BB kit on a 2012 bike.

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Athena is good quality stuff. Certainly not the cheapest. Usually comes with a Woosner forged piston and larger water jackets in the cyl. It shouldn't be a problem with the crank on a Yamaha.   You might want to add a cam or it will be a mid range monster.

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Athena is good quality stuff. Certainly not the cheapest. Usually comes with a Woosner forged piston and larger water jackets in the cyl. It shouldn't be a problem with the crank on a Yamaha.   You might want to add a cam or it will be a mid range monster.

 

Yea it helps that I can get the kit at cost.  Intake, Exhaust or both?  Yamaha crank is pretty tuff then I guess. 

Edited by yammaxx

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Yea it helps that I can get the kit at cost.  Intake, Exhaust or both?  Yamaha crank is pretty tuff then I guess. 

 

Unless the crank is a known weak link. However have not read that. It should be as reliable as the DRZ. I would change both cams.

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Unless the crank is a known weak link. However have not read that. It should be as reliable as the DRZ. I would change both cams.

Ok, thanks!  Any suggestions on cams?  It's  supermoto bike, not mx. 

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Ok, thanks!  Any suggestions on cams?  It's  supermoto bike, not mx. 

 

Some of that depends on you. How you ride the bike and what you expect out of the top end performance. Usually a big bore increases a lot of mid range punch, then you can add top with the cams. A stage two might be good. Should likely be ported to really take advantage out of the whole package. If you do use someone that does or has experience with that head or a lot of bikes. 

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I think you will also need someone that knows what they are doing to adjust your fuel injection.

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I think you will also need someone that knows what they are doing to adjust your fuel injection.

Ok, thanks. I ran RHC cams in my DRZ, but im not sure if Ron Hamp makes cams for the YZ.  Yea the bike will be going to the dyno after it gets put together.  Thanks again!

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What I want to avoid is having to replace crank, or causing the crank bearing to wear out faster because of a big piston flying around in there.  I know on a DRZ you can go to a 434 from a 400 and you don't see anymore wear on the crank  then a stock setup.  I'm just not a familiar with the 450f engine, so before I do something I regret, I want some opinions from guys that have actually done a BB kit on a 2012 bike.

 

The crank is strong enough, easily, but you will probably be happier with things if you get a balance job done.  Wear will increase due to the extra load, naturally, but I doubt you will notice any significant reduction in the normal service life of the crank, even so.

 

Athena makes a good product.

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The crank is strong enough, easily, but you will probably be happier with things if you get a balance job done.  Wear will increase due to the extra load, naturally, but I doubt you will notice any significant reduction in the normal service life of the crank, even so.

 

Athena makes a good product.

Thanks for the help!

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Athena 102 kit is on the way, I'll let everyone know how I like it.  Thanks for everyone's help!

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Athena 102 kit is on the way, I'll let everyone know how I like it.  Thanks for everyone's help!

Interested to know how you like it and your whole set-up and what you went with cams too? Im thinking of building up my 2010 yz450f motor and not sure what too do.. Bike is set up on my  snowbike kit  so need power everywhere as the track kits robs alot of HP plus the change in elevation doesnt help either as we ride at 2000-6500 feet 

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