Athena Big Bore Kit

$291.99 - $1,295.99
$250.99 - $1108.99
4.60 out of 5 stars
Fitment Expert:
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Athena Big Bore Kit
Athena Big Bore Kit
  • Description
  • Reviews (22)
  • Q&A (122)
  • Fitment

Athena offers a wide range of cylinder kits for scooters and motorcycles with diameters and portings completely re-designed as original spare parts and / or specific boost to be used on tracks. In particular, racing kits consist of lighter pistons with a flat head, special portings, exhaust bridge, and a new cylinder head designed to increase the compression ratio and improve internal combustion. For some models Athena also supplies special long stroke racing kits complete with crankshafts and reinforced connecting rods.

The Athena Big Bore kit is the missing source for increasing your motorcycles raw power.

  • The included cylinder is constructed out of aluminum with a nickel-carbide coating to increase durability.
  • The water jets have been widened for a higher flow rate, keeping the cylinder cool.
  • Athena built a reliable cast piston that has been molybdenum-coated for high performance use and extended wear life.
  • Includes a specially designed gasket kit to accommodate the big bore features.
  • Each kit also includes easy-to-follow step-by-step installation instructions.
  • Notes: Some kits will require case boring. Kits for 4-stroke applications do NOT include cylinder head. Image is for display purposes ONLY and may not represent actual product.
4.6 out of 5 stars (22)
4.6 out of 5 stars
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Overall 5 out of 5 stars
edgrrr
Great Bark

I have 2 2004 CRFs, one stock and one big bore. Big difference in power and really aggressive bark. Much more torque on hand. You have to have intake valves on spec to start the extra displacement. I may go for kibblewhite valves to keep the compression over time.

Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: Missouri, USA
rmz490
Great item!..check your gaskets..

installed 4 of these kits. last kit on kx450. finished install. warmed up. cooled down. warm up. engine was quite and responsive. then I see that my engine oil is milky.. tear down. not fun the second time!! found small piece of gasket flash cut from coolant passage in center of the 3 piece head gasket. in the area between oil galley hole and coolant. see pics. contacted motosport and they helped me out and sent a replacment gasket set at no charge!!!. great customer service. replaced head gasket and ready to go!!! so check you gasket. the head gasket is a 3 piece riveted assy. just pull it open and inspect before installing.. thanks motosport!!

Overall 5 out of 5 stars
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Ease of Installation
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Verified Purchaser
Location: Richlands, NC
NC762
Awesome Big Bore Kit

This was a good price and excellent investment. Put it in a CRF150RB, the power range was increased all the way around, low, mid and high. Be aware that you will need to run at least 96 octane fuel with the big bore kit.

Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Location: San Diego, CA USA
Daoedsjah
Use circa clips provided

Installed on a YZ250F. Loads of power. Was able to keep up with 450s. Easy to install. Use the circa clips provided by Athena. I made the dumb mistake by listening to a earlier review by using stock circa clips but they came out and ruined my cylinder and piston. Use Athena's. They do extensive R&D with their products to include their clips. Wasn't Athena's fault at all. All my own. Got the new (discounted) kit in there and I'm back to full power. Of course do a valve adjustment with the swap for optimal power. Now I do have hot cams so my power is extensive.

Overall 5 out of 5 stars
Durability
Ease of Installation
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Power
Style
Verified Purchaser
Location: Moorpark Ca
JMReeves
Gear head

I have used the Athena kit before. The quality is the best. It does require machining of the engine case to work properly. To do it right you must split the engine cases. The performance and reliability is great. To get the most performance from the kit I used an FMF Fatty pipe and powercore 2 silencer. Jetting the carb a lot richer is a must for reliability. Installation by a qualified experienced mechanic or gear head is a must for good results.

Overall 4 out of 5 stars
Durability
Ease of Installation
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Location: waipu New Zealand
ge00
For experinced rider!

the athena 144 kit is great! adds heaps of mid range 2 the bike and still pulls up top. However good mechanical knowledge is needed for the installation and if you cant keep your 125 on the pipe dont bother. Time with your butt in the saddle will give you far beter advantage over your competion than this kit! cheers!!!!!

Overall 5 out of 5 stars
Verified Purchaser
Location: Pomona NY
carpenter197

Overall 5 out of 5 stars
Durability
Performance
Power
Style
Location: milford, nj
Austin98
Awesome power

this kit is great i have it on my 07kx250f it gives you tons of power. you may need to do a few other things so the bike runs right though, i had to jet mine, a bigger bowl on the carb, loudmouth intake and some fine adjustments to keep up with it. drd exhaust helped too. but once you iron out any kinks it is unreal, my friend as a 490 kit in his rmz450 and i stick with him on starts. it also runs really hot i had to get a boyesen high flow water pump to keep it cooler. best if you dont let it idle or get too hot if you stall it it will be a rough time kicking it over again.

Overall 5 out of 5 stars
Durability
Ease of Installation
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Location: Florida
4bz1d1a
Athena Kit...

Bought the Athena kit as a base to start a stroker build on my '07 LTZ 400. The Athena kits are really high quality, and have been around a long time. You will not be disappointed..

Overall 1 out of 5 stars
Location: Troutdale, OR
MotoRon38
Athena 290cc Big Bore Kit

Nothing but problems with my new bike since installing the big bore kit. MotoSport doesn't tell you, but when purchasing this kit, you must also then spend an additional $500 in purchasing a new black box, as the stock one isn't compatible with the 290cc kit. Had I known this, I wouldn't have purchased the BigBore Kit.

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Total Questions (122)
Questions with answers:
  121
Questions without answers:
  1
Yz85 2010?...
jake Location: Australia
1-10 of 122
10 days 8 hours ago Location: Dickinson, ND 58601, USA
What kind of compression ratio would it have for a 2008 250 xcfw?
Steve 1 month 7 days ago
Do I need to get it honed for the 130cc kit on an 03 drz110 or is it direct fit?
MotoSport Staff Expert
1 month 6 days ago
MotoSportExpert
This would be a direct bolt on kit for your 2003 Suzuki DRZ110. There would be no case modifications needed.
guido 1 month 16 days ago
Will this fit my 2001 yz 125?
Expert MotoSport Staff
1 month 13 days ago
MotoSportExpert
Yes. Just be sure to correctly select the Year/Make/Model of your bike before ordering so we can be sure to send you the correct kit for your bike. Also, feel free to give us a call at 888-676-8853 and we would be happy to help you out with your order.
jake 1 month 21 days ago Location: Australia
Yz85 2010?
hi would I have to do any machining to the cases to fit the big bore on my yz85 2010 model
MotoSport Staff Expert
1 month 20 days ago
MotoSportExpert
Yes when installing the 105cc or 112cc kit on the YZ85 machining of the engine case halves is required. (see instructions) http://www.athenaparts.com/files/pdfs/P400485100038.pdf
AJBFire 1 month 25 days ago Location: MA
Fuel Type Needed?
In the directions it says you need greater than 96 octane. Is this true? I have been running VPR, which is like 101 octane.
Expert MotoSport Staff
1 month 25 days ago
MotoSportExpert
Yes, for optimum performance you want to follow the manufactures recommended directions.
Tuzman 1 month 26 days ago Location: Amarillo,tx
Does ring end gap have to be checked or are they prefit?
MotoSport Staff Expert
1 month 25 days ago
MotoSportExpert
Athena Instructions: http://www.athenaparts.com/files/pdfs/P400510100007-008.pdf
Bryan 2 months ago Location: Shetland
Will this fit into my standard 2004 kawasaki kx 65?
Expert MotoSport Staff
1 month 27 days ago
MotoSportExpert
Just be sure to correctly select the Year/Make/Model of your bike before ordering so we can be sure to send you the correct kit for your bike. Also, feel free to give us a call at 888-676-8853 and we would be happy to help you out with your order.
pittermod 2 months 16 days ago Location: Minnesota, USA
Will i have to do any case boring on a 2005 suzuki drz 110?
MotoSport Staff Expert
1 month 24 days ago
MotoSportExpert
No case boring would be needed to run this kit on your 2005 Suzuki DRZ110.
dustin 4 months 7 days ago
What all will I need to put this kit on my 2014 kx 450f and what will I need to change after the kit is put on to make my bike run correct?
Expert MotoSport Staff
2 months 9 days ago
MotoSportExpert
This Athena Big Bore Kit would come with everything you need to install on your 2014 Kawasaki KX450F. Additional tuning may be necessary, depending on your current settings and riding conditions, for optimum performance.
Hoffman889 4 months 12 days ago Location: Pa
Does this require machining to fit on a 2013 yz250?
MotoSport Staff Expert
4 months 3 days ago
MotoSportExpert
No there should not be any additional machining required on your 2013 Yamaha YZ250. You can find the installation instructions here: http://www.athenaparts.com/files/pdfs/P400485100042.pdf
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