Wiseco Big Bore 440 Kit

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Displaying parts for your 2003 KAWASAKI KFX 400

Wiseco Big Bore 440 Kit
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Wiseco Big Bore 440 Kit

Fits: 2003 KAWASAKI KFX 400
Part# 1038390003

Our Price: $276.24

Get $13.82 in Quick Cash

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2 In-Stock

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Additional Videos

How to - check piston ring end gap

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

How To - Hone A Cylinder

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

RM YouTube Channel


Special Notes:

Notes for Kit: Wiseco Big Bore 440 Kit

  • *94.5mm piston, 12.5:1 compression ratio.
  • This kit includes all the necessary parts needed to increase your engines displacement to the largest reliable engine size.
  • This kit has been proven through the rigors of competition to be reliable and offer an impressive power increase .
  • Kit includes piston kit, big bore sleeve as well as the head and base gasket .
  • Engine displacement is increased to 440cc .
  • Professional bore and sleeve installation is required.

Wiseco Big Bore 440 Kit Reviews

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4.9 / 5.0
7 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
5.0 / 5
5.0 / 5
5.0 / 5
5.0 / 5
Recommend it?
Yes (1)
5 / 5
5 / 5
5 / 5
5 / 5
Recommend it?
Great big bore kit for the ltz 400
Very great product huge power gain

April 29, 2018
Homer, OH, US
Age: 15-24
221 - 250 lbs.
5'7 - 5'9
Best mod ever
This was buy far the best upgrade I did to this quad. Great fit.

Machine this part was bought for: 2002 HONDA TRX 400EX
January 13, 2015
95610, CA, US
Age: 25-44
RMATV customer service and product performance
Very dissappointed in the knowledge of the RM sales team. They told me that all I would have to do (to my 2004 400ex) was press out the old sleeve and press the new one in, however that was not the case. The machine shop had to press out the old one, bore and counter bore the cylinder in order to press the new sleeve in, then after getting the cylinder back I went to put it all together just to find out that the sleeve had to be bored to the piston also. Wasn't very costly to have done ( about $120) but would've been nice to have known all this from the start. Wisecos 440 big bore kit is the bomb tho, along with hot cams stage 2 cam and a dyno jet jet kit my quad is wicked fast.
June 26, 2011
I would definitely recommend it
I put this kit in my 04 XR 400. It gave it more power through out the rpm range. But way down low was where I really noticed an improvement. I can really lug the motor down through extreme technical sections on the trail now and with out having to slip the clutch. I noticed I could even run a gear higher which settled down the suspension which in turn made me able to go faster. I did have to use a ring compressor to install the piston though.
July 29, 2010
KFX 400
for the money its worth it! my 400 has about every mod you can think of. before i could compete with the 450's! now i can blow them away! even some 500's!
December 27, 2009
Excellent. must have
Very awesome upgrade. definitely a power notice
November 29, 2007
its great
October 23, 2007
Each question or answer submitted enters you into a:
$100 gift card monthly drawing and a
$500 gift card quarterly drawing!
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Browse 3 questions Browse 3 questions and 4 answers
How you put the sleeve in in the head?
Christian G on May 30, 2017
BEST ANSWER: Had to take to machine shop to have it installed was around 200 dollars but that's they only way to have it done right because there's is a lot involved in installing it properly
Is the sleeve in this kit aluminum or steel?
A shopper on Apr 22, 2018
BEST ANSWER: This is going to be an aluminum sleeve.
How reliable is it?
A shopper on Nov 12, 2017
BEST ANSWER: Has worked out great much more power
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