Cylinder Works Big Bore Kit

$549.99 - $649.99
$499.99 - $599.99
4.30 out of 5 stars
Fitment Expert:
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Cylinder Works Big Bore Kit
Cylinder Works Big Bore Kit
  • Description
  • Reviews (7)
  • Q&A (24)
  • Fitment
  • Unlock your ATV's hidden potential with the power producing and durable Cylinder Works big bore kit.
  • No need to waste your time and money on getting your factory cylinder bored out because the Cylinder Works cylinder is stronger and more reliable. Best part about this cylinder is that it mounts directly to the factory crankcase and head.
  • The piston and rings that come with the Cylinder Works big bore kit are reliable for any motocross race.
  • Even down to the gaskets Cylinder Works employs high quality gasket materials for reliability.
  • Take your 450cc engine and add 3mm for a big bore 479cc with the Cylinder Works kit.
  • The Cylinder Works big bore kit includes: big bore cylinder, big bore piston, piston pin, piston pin rings, gasket kit.
  • Note: to achieve optimum performance re-jet the carburetor with the available jet kits.
4.3 out of 5 stars (7)
4.3 out of 5 stars
5 star   4
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3 star   1
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1 star   1
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1-7 of 7
Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Location: Johnstown, PA, USA
Poe1
Great torque

This kit + stage 2 hot cam + head porting = awsome

Overall 5 out of 5 stars
Location: Manistee,Mi
DrWoj
Excellant Kit

I own a motorsports repair shop,customer brought a TRX-450 in that needed a crankshaft and top-end. Thanks to Motosport we were able to rebuild the motor with better parts than stock and save some money at the same time. We have a test track here and before the customer picks up his machine we like to have him or her take a few laps. When they get off their machine and there is a smile from ear to ear you know they are pretty happy.This particular unit the customer was realy impressed. The big bore kit realy woke up the TRX. Thanks Motosport

Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Location: north jersey
hwy2hll
Perfect fit

works great easy installation everything was there

Overall 1 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Location: whidbey island WA
PWR70
Problem purchase

Purchased this kit for my 2006 YZ 250F and it took two tries to get a piston and ring combination that fit (rings would not fit in the grooves) finally sent me a piston that worked but it did not have the moly coating. Excellent power gains unfortunately it is on its 4th head gasket due to a poor alingment with the cylinder head allowing the gasket to hang over the combustion chamber. this was possibly the worst purchase I ever made and nobody is willing to stand behind the product, better off buying a Athena kit.

Overall 5 out of 5 stars
Ease of Installation
Performance
Power
Style
Top 1000 Contributor
Location: Rigby, Id
yzbigbore

I installed this on my 06 yz450f it looks just like the OEM cylinder i did not install the piston instead i ordered a high compression piston. This bike runs like i added another 10 HP. I have been riding it for 3 months with no problems. hill climbing you can't run out of power. power is strong all the way through i would recommend this product.

Overall 3 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Top 250 Contributor
Location: Phoenix, AZ
hayder
It's your call

Had some prblms with it.. to start off i have built over 15 yfz motors with no prblms so it wasn't me.. but back to the product. First problem I had was the piston pin clip came out and put a gouge in the cylinder so i went and got another cylinder and rings and clips and maybe had 10 hours on it and I broke a valve which went through my piston and as i tore it all apart again I also noticed that the inside of the cylinder had a crack in it. It could have been from the valve but i dont think so because the valve went through the piston and ive read about the cylinders cracking on other people too. so just thought I'd say if you wanna risk it go for it had lots of power but if you want something that will last i would go OEM. thats where I'm headed now.

Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Location: aberdeen, nc
jwells147
Very nice

Quality construction, made a huge difference in power. probably the most cost effective way to mod a 250f. I did have to rejet with a JD jet kit after i installed this; before it really ran to its potential. Was popping on decel and throttle response was not as crisp. after the bike was rejetted it is a monster.

1-7 of 7
Total Questions (24)
Questions with answers:
  22
Questions without answers:
  2
1-10 of 24
7 days 3 hours ago
2006 CRF250R 269cc kit case modifications?
Are there any case modifications that need to beads to the cases for use on a 2006 CRF250R?
7 days 3 hours ago
2006 CRF250R case modifications?
Are there any case modifications needed for the 269cc kit to fit a 2006 CRF250R?
CPruett57 1 month 11 days ago
Is there more to know about how long this would last?
Is there an estimated time that this would last you? Or is that more dependent on how you ride the bike?
Expert MotoSport Staff
1 month 10 days ago
MotoSportExpert
There are too many variables to say how long it would last. That would be determined on how the bike was ridden, maintained and serviced as well as riding conditions.
jchampion Over 7 months ago Location: Hanover, MI, USA
Do the valves need to be replaced with big bore kit?
Im thinking about purchasing this for my 06 Yz450f and i am wondering if i will have to replace my valves? Is there anything else besides rejetting that needs to be done or is this a bolt on rejet and have a blast kind of kit?
Top 1 Contributor
Over 7 months ago
MotoSportExpert
Unfortunately we at Motosport.com are not able to give you repair advice. We highly suggest that you purchase an OEM service manual for your machine and refer to it to answer your repair questions. If you need more assistance, please consult a local repair shop to further assist you in your repairs. If you need parts to assist in your repairs, we are happy to assist you with your parts order.
Top 500 Contributor Top 1000 Contributor
garrettcibak Over 8 months ago
2012 CRF250R durability?
How much stress will the 270 kit put on the rest of my motor? I know it will add a bit more,but will I have to worry about engine parts wearing out soon?
MotoSport Staff Expert
Over 8 months ago
MotoSportExpert
That is hard to say since there are so many other variables that go into engine wear and life. Generally High Performance Big Bore motors do wear faster and are less reliable.
donmx109 Over 11 months ago
Why is this kit lower compression than oem 2008 kx250f?
Stock 2008 kx250f has 13.5:1 compression ratio. This kit is drops compression to 12.6:1. On stock bore this compression drop would equate to .7 to .8 horsepower loss. This loss would also show up on the big bore kit as well. Why would cylinder works spec a piston with lower compression?
Top 1 Contributor
Over 10 months ago
MotoSportExpert
Cylinder Works Big Bore Kit are specifically designed for each machine to maximize Horsepower and reliability. A big bore kit is not about Peak HP but more low end usable power on your 2008 kx250f Kawasaki.
Trx450rrider Over 11 months ago
05 trx450r big bore and stage 1 cams?
I have an 05 trx450r with normal mods. Im looking to buy the 479 big bore and stage 1 cams is this gonna give me a decent power increase or is there something different i should do? I plan on doing other performace mods also
Top 1 Contributor
Over 10 months ago
MotoSportExpert
The internal combustion engine is very simply put a basic air pump. The more air/fuel you and intake and exhaust from the motor, the more power you will make. HP gains are very subjective to gauge on any one or combination of performance parts. Things like the age of the motor, the tune of the air fuel ratio, the altitude, etc will all have an effect on PEAK HP numbers. Many performance products will not increase your PEAK HP, but rather move the HP to a different RPM range than the stock motor.
Poe1 2 years 3 months ago Location: Johnstown, PA, USA
What fuel should I use with this kit?
My bike is a 2002 crf450 I have a cylinder works big bore kit , stage2 hot cam , Tokyo mods carb , hot rods crank and the head has been ported . I hill climb , trail ride and sometimes drag race. I currently use VP110 , is this fuel a good choice? Thanks for your time
MotoSport Staff
2 years 3 months ago Location: Portland, OR, USA
MotoSportExpert
For any 4 stroke motor that is not running incredibly high compression you will actually not want to run anything over 100 octane. With fuel over 100 octane it will burn too slow and too cool, and you can actually start to lose power. The VP110 is a great option for fuel, but for your application i would mix it 50/50 with a premium pump fuel. The best option would be if you can utilize a non-ethanol pump fuel if available in your area. With mixing the 110 with a premium fuel, it will give the fuel some consistency that can be lacking in the fuel found at the pump. For all intents and purposes though, this kit would run fine on premium pump gas alone with the correct jetting.
Jymmyee 2 years 3 months ago
Does this kit need additional tuning for a ltr450, I have a cherrybomb right now ?
MotoSport Staff
2 years 3 months ago Location: Portland, OR, USA
MotoSportExpert
This kit will require more tuning capability than what the cherrybomb provides on the LTR450's. If you go with a Power Commander you will be able to get that tuned and running correctly with the big bore kit.
Jimbo 2 years 4 months ago Location: Anderson, SC, USA
My son has a 2006 Kawasaki kfx400 bored 48 over with custom jet kit for the exhaust and bore kit. Now the battery drains while he is riding.?
My son has a 2006 Kawasaki kfx400 bored 48 over with custom jet kit for the exhaust and bore kit. Now the battery drains while he is riding. Any idea what could be causing his battery to drain and what might fix it?
MotoSport Staff
2 years 4 months ago Location: Portland, OR, USA
MotoSportExpert
Electrical issues can be tough, for this I can say that the modifications done to the ATV would not cause this problem. I would start with checking the regulator/rectifier. From there I would check the stator. If you are unsure how to check these items, a service manual would have the instructions or your local dealership can also perform a diagnostic.
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