2011 Honda CRF250R Athena Big Bore Kit - 280cc

Product Description

The Athena 280CC Big Bore kit is the missing source for increasing your motorcycles raw power.
The included 280CC cylinder on the Athena Big Bore kit is constructed out of aluminum with a galvanic coating to increase the durability. The water jets have been widened for a higher flow rate, keeping the cylinder cool.
Athena built a reliable forged piston that has been molybdenum coated for high performance use and extended wear life.
The Athena Big Bore kit includes a specially designed gasket kit to accommodate the big bore features.
Another great feature of the Athena Big Bore kit is that it bolts on with no machining needed, and includes easy-to-follow step-by-step installation instructions.
The Athena 280CC Big Bore Kit includes: cylinder, piston, ring(s), pin, clips, top end big bore gasket kit.

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Overall

Over 5 years ago

hondaider279

Amazing

Awesome part. Gave me alot more horsepower and a definately noticable difference in the corners. Overall worth every penny.

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Questions with answers:
Total Questions	(14)
	13
Questions without answers:
	1

Have a question?

“ What does a big bore kit do?... ”

Location: Martinez

“ Is it necessary?... ”

Location: eastern kentucky

“ Is there any new parts or changes that need to be made?... ”

1-10 of 14

Blade 6 days 20 hours ago Location: Quebec, Canada

The original jetting os good or no good whit big bor?

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2 years 11 months ago Location: Martinez

What does a big bore kit do?

I ride a 2004 CRF250X. Would the Athena 280cc big bore kit be worth installing on my bike?

MotoSport Staff

2 years 11 months ago Location: P+RTLAND

Drewski

Your going to a bigger cylinder and a bigger piston so your getting a lot more power than your stock 249cc set up. If you bike is bone stock, I wouldn't recommend it. If you aren't happy with performance on your bike and have already knock out the exhaust and air filter, then I would go with it. If you haven't done any of that stuff yet you may want to before hopping up to the big bore kit.

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motox174 Over 3 years ago Location: wasilla, ak

Is the piston included a high compression pistion??

Expert MotoSport Staff

Over 3 years ago Location: Portland, OR

james718

The piston itself is not a Hi-Compression piston.

Over 3 years ago Location: Oregon

redrider73

The instructions that came with it says to use 96 octane or higher...so I'm going to mix VP110 and premium pump gas at a 50/50 mix. Also, when comparing the stock 06 CRF250R piston to the Athena piston, the top of the Athena piston is machined down deeper for the valves to clear, just like they would be for a high compression piston. Also a note for installation: the dowels that go between the cases and cylinder need to be machined down about a millimeter to allow the cylinder to sit all the way down on the cases. Not a big deal but it saves time to do this before you put the cylinder on.

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WhiteGold Over 3 years ago

Is it AMA legal?

I want to put this kit on my bike. I was just wondering because I will race with it. I don't know if thats a stupid question or not, i just need to know if its AMA legal.

MotoSport Staff Expert

Over 3 years ago Location: Portland, OR

james718

Unfortunately you will want to ask this question to the AMA. But, I do know this wouldn't be legal in the "stock" class, but that's obvious.

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eastside Over 3 years ago Location: oahu

Is it bolt on?

any modifacations you have to do

MotoSport Staff Expert

Over 3 years ago Location: Portland, OR

james718

you will receive everything you'll need to install this kit.

Top 500 Contributor

Over 3 years ago Location: Orange County, CA

Fast450R

I used the Athena 490 kit for my 450R. BEST MOD EVER! Power, no problems. Excellant. And yes, it bolts on. no other mod needed (other than a rejet)

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chrisb0879 Over 3 years ago

Does this come with directions?

MotoSport Staff

Over 3 years ago Location: P+RTLAND

Drewski

Yes, directions are included.. If you haven't done any mechanical work with a top end before I would recommend having a professional mechanic install this kit.

Top 500 Contributor

Over 3 years ago Location: Orange County, CA

Fast450R

yes, but if you need instructions........you really shoudl pay someone to do it for you. OR...buy a Clymer Manual.

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dustin07 Over 4 years ago Location: eastern kentucky

Is it necessary?

to buy a bigger water pump, and new pipe when using this bore kit with harsh offroad use on a crf 250x

Expert MotoSport Staff

Over 4 years ago Location: Portland, OR

james718

A larger water pump wouldn't hurt, but I would say it's not necessary.

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dustin07 Over 4 years ago

Is there any new parts or changes that need to be made?

to a stock crf 250x before you run it with the big bore kit

MotoSport Staff

Over 4 years ago Location: Por+land

Drewski

All the parts needed should be included. Down the road you might want to look into maybe a stage 2 cam but everything should be included with this kit in order to run it.

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Shad0w Over 4 years ago

For a 2005 crf250r?

which hotcams camshaft would you recommend to go along with this kit, stage 1 or stage 2. i'm also going to be getting the kibblewhite valves (both intake and exhaust) as well as the valve springs. I would also be getting a jet kit for after its all assembled to accommodate for the larger volume.

MotoSport Staff Expert

Over 4 years ago

james718

That Big Bore kit is going to give you more bottom end than what you have stock. with that said, I would recommend the Stage 2 as that will even out the power and help out the mid to top. You can also look into the Stage 3 as that was designed to work with Big Bore Kits. I hope that helps.

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MotoKid217 Over 4 years ago Location: salisbury NH

What is the horse power increase when installing the 280 kit onto a crf 250?

MotoSport Staff Expert

Over 4 years ago

james718

Sorry we don't have dyno's to test for HP. That would be a question for your local service dept. tech.

Over 4 years ago Location: Indy

Unklemakk

According to Athena's catalog. they list stock rear wheel HP as 32.9. with the Big Bore Kit 38 RWHP

Over 3 years ago

grannyjoan

what us the horse power increase when installing the 280 kit onto a kx250f.

Answer this Question

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Athena Big Bore Kit - 280cc

Product Description

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