This site has limited support for your browser. We recommend switching to Edge, Chrome, Safari, or Firefox.


KFX450 KFX450R 100 mil Big Bore Stroker Complete Rebuilt Motor Rebuild Kit 520cc


Compatible Vehicles
Submodel Year Make Model
-- 2014 Kawasaki KFX450R
-- 2013 Kawasaki KFX450R
-- 2012 Kawasaki KFX450R
-- 2011 Kawasaki KFX450R
-- 2010 Kawasaki KFX450R
-- 2009 Kawasaki KFX450R
Monster Energy 2009 Kawasaki KFX450R
-- 2008 Kawasaki KFX450R
  • 100mm Athena or OEM big bore cylinder
  • 100mm CP or JE forged piston**
  • Hi temp piston rings
  • Chrome wristpin
  • Circlips
  • Hotrods +3mm stroker crank with rod assembled
  • Main/crank bearings
  • Crank balancer bearings
  • Transmission bearings
  • Clutch bearings
  • Shift cam bearings
  • Water pump bearings
  • Complete gasket kit - head base exhaust case covers pump covers
  • MLS big bore head gasket
  • Complete crankcase oil seal kit
  • Valve stem seals
  • Water pump mechanical seal
  • Water pump impeller
  • Cam chain
  • Clutch kit
  • K&N oil filter
  • NGK spark plug
  • Maxlock TITANIUM head stud kit - LIFETIME WARRANTY* 
  • Stickers
  • Piston uses pump or race gas
  • No case machining required
  • Everything comes new in the original packaging
  • Manufacturers warranty applies*


Office hours are Monday to Friday 7am to 4pm PST.  Call, visit us online, or in person from 7am to 4pm at 1538 Howard Access Rd, Suite A, Upland, CA 91786.  We accept all forms of payment – Major credit cards, Paypal, Venmo, Cash App, personal or business check(once cleared), and cash money.

**We stock parts that are the same quality, price, and have the same specifications from different manufacturers so that when back orders occur, like they have been for the last couple of years, we have an alternate part to send you.  That is the only reason your order may arrive looking slightly different from the photos.  We never substitute a cheaper part for an original and if you want a certain brand just ask and we will make sure you get it. 

Payments:  We accept all forms of payment – Cash, MC, AMEX, VISA, DISC, PayPal, Venmo, Cash App, among others.  Payment can be made online or over the phone or in person. 

Returns: Returns are accepted within the first 30 days as long as the order is sent back to us BRAND NEW, NEVER INSTALLED, 100% COMPLETE, AND IN THE ORIGINAL PACAKGING.  Any item returned after installation is not eligible for a refund.

 *Warranty:  This product is NOT DIY.  Over 99% of people in the world are not qualified to build an engine.  We ALWAYS STRONGLY recommend parts be installed by a qualified, experienced mechanic.  STUD WARRANTY: If for any reason a stud fails during use, not installation, we will send an entire new stud kit.  No other parts or any labor are included, and it can not be converted to a refund or discount on any order.  Studs must be returned to us for inspection first.  ALPHA CUB WARRANTY: If your Alpha Cub cylinder fails for any reason not related to installation, tuning, break in, or misuse we will fix the cylinder free of charge.  If it can not be fixed we will supply you with a new one.  For any warranty to be considered the part(s) in question must be sent to us for inspection, no exceptions.  We do not warranty parts solely based on photos, phone calls, emails, what you read online, or what another mechanic says the issue is, and we can not warranty parts that fail due to improper installation, tuning, break in, maintenance, or abuse.  The truth is that 99% of failures result from the parts not being installed correctly. 

Feedback: Positive reviews and feedback are greatly appreciated.  We have changed the way we do business in response to customer concerns and receiving positive feedback when an order goes the way it is supposed to is a huge help.  If you do not feel we deserve positive feedback or reviews just contact us and we will do what is needed to help you feel as "positive" as possible about your experience.  To make it worth your while we will give you 10% off your next order for taking the time to leave us 5-star positive feedback.  That could be hundreds or dollars for 1 minute of your time!