Athena Big Bore Kit
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Athena Big Bore Kit

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Additional Videos

How To - Rebuild The Top End On A KTM RFS Motor (Part 1)

How to - check piston ring end gap

How to - Four-Stroke Top End Rebuild (Part 2)

How to - rebuild the top end on a motorcycle or atv (Part 2)

How to - rebuild the top end on a motorcycle or atv (Part 1)

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  • Athena cylinder kits are a bolt on performance replacement kit specifically designed for each model, with no machining required.
  • Kits include a nickel carbine coated cylinder designed with wider water jackets, complete piston kit and a top end gasket set.

Athena Big Bore Kit Reviews

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1 of 1 people found this review helpful.

Athena 290 big bore wr/yz

Comments On Oct 12, 2011:I have ran this big bore for three years and have great success with it, makes great bottom end and mid range power. I have ran it on my 08 yz250f with a wr trans and rekluse clutch and hot cams, awesome woods bike.

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0 of 0 people found this review helpful.

lost topend, but added cam to regain

Comments On Aug 27, 2011:installed on a 2005 crf250 - lost top end, but regained with a hotcams stage2 cam. awesome everywhere, but sometimes hard to figure out jetting.

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0 of 0 people found this review helpful.

This Kit Absolutely Rips

Comments On May 15, 2011:Put this in my 2007 RMZ250 along with Intake and Exhaust Hotcams. It feels like I bought a new bike. With the big-bore I have the low end and midrange to blow up any berm. The Hotcams give me the top end that doesn't fall off either like some big-bores can. This is all with the stock pipe and silencer with a Pro-Moto Billet Endo's spark arrestor to quiet it down so I am <96db for Hare Scrambles racing. Don't waste money on a pipe get the big bore.

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3 of 3 people found this review helpful.

More Power!!! Wow!

Comments On Apr 09, 2011:These are great! Put the 490cc kit on 2 crf450x's and wow! Incredible increase in power! We also put in the Hot Cam stage 2 with both big bore kits. The bikes sing! What suprised me most was the low end torgue and lugging ability with the 490CC kit. I thought it would be uncontrolable on techical single track stuff, but it's just the opposite. Great control down low and lots of mid and top end power! These bikes climb everything. Make sure you break them in good. At least 3 warm up and cool down cycles before you work them hard. Otherwise, you'll be putting in a new set of rings.

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0 of 0 people found this review helpful.

Swapped torque for revs

Comments On Nov 19, 2010:Application '05 Yamaha WR 250F w/pro-motto-billet quiet insert in stock exhaust. My goal was to give me more power for the sand and straight sections in Desert racing. Result more grunt down low and big improvement riding a gear high through whoops. Overall my top speed seemed to suffer. Conclusion: For Desert Racing not worth the money, for Woods riding totally worth it. Installation excellent. Durability incredible! Installed 03/2007 prior to a 10-race Desert Series. 2008/09 and 2010 averaged 60 hours/year ride time and competed in 3 additional Desert races. Today 11/2010 original Athena piston going strong.

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0 of 0 people found this review helpful.

bad set up for yz125/144

Comments On Oct 09, 2010:do not buy this kit for the YZ125 unless you are ready to split the case and do some grinding and do not buy the kit unless you can get the new 1 part head . the older 2 part head will give you nothing but blown head gasket after blown head gasket

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1 of 5 people found this review helpful.


Comments On Aug 13, 2010:Dont bye this To much money for what it does

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0 of 0 people found this review helpful.


Comments On Jul 07, 2010:i have bought this product and it works great!! no problems only install and run!

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1 of 1 people found this review helpful.


Comments On Mar 30, 2010:i recently purchased an 03 yz250f which needed some work so for a little more money and less work i went with this big bore and a hot rods crank. the bike already had hot cams in it. i havent ridden it a whole lot yet but so far its been like riding a pissed of little yamahama.

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0 of 0 people found this review helpful.

Best performance for the money!

Comments On Oct 29, 2009:I installed this big-bore kit on my 2006 YZ250F with no other modifications jetting, cams, pipe, timing or NOTHIN'! It bolted right on, everything fit perfectly, and the improvement in power is much better than any pipe could give! Don't waste your money on a pipe! Buy this!

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