Build: Jamie Ellis/Twisted Development

Text: Kris Keefer

Video/Photos: Simon Cudby

The Kawasaki KX450 got a bad rap in 2025 with Jorge Prado, but as I was leaving Loretta Lynn's last year, I picked up a phone call from Jamie Ellis from Twisted Development, mentioning he wanted to build a KX450 for me named Roxy to test. That phone call last August put this build in motion that you see here! In stock form, the KX450 is a mellow, somewhat lethargic 450, but with a little work, it can be transformed into a healthy machine that is fast enough for most. With this Garage Build, we wanted to take it a step further and really dive into the engine to see what Jamie and crew could dish out. Could Twisted Development build me a KX450 that is so fast that it would be unridable? Would I even like the type of power that it builds? "Roxy" absolutely changed the way I thought about KX450s in general. Below is how she became the boss of the garage/shop.

Parts Used:

Twisted Development

Headwork/Epoxy Porting, Custom J&E/TD Racing Piston, Custom Valves, Valve Seats, HC Piston, Custom Camshaft, Mapped Vortex ECU, Throttle Body, Transmission Polish
td-racing.com

Pro-X

Connecting Rod Kit, 13/50 Sprockets
proxparts.com

DID

ERT3 Gold Chain
didchain.com

Pro Circuit

Ti-6 Muffler System
procircuit.com

Rekluse

Full Apex Clutch Kit
rekluse.com

Twin Air

Power-Flow Kit
twinair.com

Ride Engineering

23mm Offset Split Triple Clamps, Anti-Twist Bar Mounts
ride-engineering.com

REP Suspension

Re-Valve/Re-Spring Suspension
repsuspension.com

Renthal

Fatbar 839 Bend, Half Waffle Soft
renthal.com

Works Connection

Open Cleat Pro Pegs, Aluminum Footpeg Mounts, Pro Launch Device, Throttle Tube
worksconnection.com

G Brakes

Front/Rear Rotors, Front/Rear Brake Lines
gbrakes.com

Dunlop

MX3SF Front 80/100-21, MX34 Rear 120/80-19
dunlopmotorcycletires.com

DeCal Works

Custom Graphic Kit
decalworks.com

GUTS Racing

Ribbed Seat Cover
gutsracing.com

Polisport

Foldable Stand
polisport.com