Yamaha Big Bore Kits

Big Bore Kits for Yamaha Mini Cycles to Thumpers

Whether your into trail riding, motocross, enduro, hare scrambles, or highway touring, we have the big bore kit you need. How many times have you thought , I wish I had bought a bigger bike? Size Matters! The short route to more power is a bigger engine. This means a larger displacement and the best way to increase displacement is an overbore kit from Kustom Kraft Performance. A Kustom Kraft Big Bore offers the most reliable way to get the power you expect. In most cases it’s just bolt it on and tune the carb and you’re off to the races (after break-in that is). Another advantage of doing a big bore kit is when your cylinder is fried a big bore kit becomes a no brainer.

Just pop your cylinder off your bike and send it to us along with the printed work order form. You’ll find the link to the order form in red above Fill it out completely and put it in the box with your carefully packed cylinder. Don’t forget to remove everything from the cylinder that’s not needed for modification. Yamaha YFM Blaster 240 cc Big bore Kit

Yamaha Big Bore Kits – 4 Stroke Off Road
TT-R125 2000-2006 145cc camshaft additional $354

YZ 250F 2001-2006 262cc $389

YZ 400F 1998-1999 420cc $450

WR 400F 1998-2000 420cc $450

YZ 426F 2000-2002 444cc $440

YZ 450F 2003-2006 470cc $449

XT,TT 500 1975-81 534cc $379

XT 600 1984-1996 635cc $409

XT 600 1984-1996 675cc case boring/not inc $449

Yamaha Big Bore Kits – 4 Stroke ATV
Kodiac 400 1993-1999 425cc $359

Grizzly 600 1998-2001 675cc *case mods not inc $429*

YFZ 450 2004-2006 470cc $449

YFM 660R 1998-01 686cc $430

Grizzly 600 1998-2001 635cc $410

YFM 700 2006-2008 714cc $525

Yamaha Big Bore Kits – 2 Stroke ATV
Blaster 1988-2006 240cc $450

Banshee 1987-2006 409cc Includes sleeving, piston, rings, pin, head mods, and gaskets include Cool Head $924

Banshee 1987-2006 409cc Includes sleeving, piston, rings, pin, head mods, and gaskets $725

Yamaha YZ80 Big Bore Kits – 2 Stroke Off-Road
Yamaha YZ80
YZ 80 1993-2004 90cc $429

YZ 80 1993-2001 104cc $429

Yamaha YZ85 Big Bore Kits – 2 Stroke Off-Road
Yamaha YZ85
YZ 85 2002-2007 104cc $439

YZ 85 2002-2007 92cc $439

Yamaha YZ125 Big Bore Kits – 2 Stroke Off-Road
Yamaha YZ125
YZ 125 1989-2006 134cc $449

YZ 125 2005-2013 144cc $449

Yamaha YZ250 Big Bore Kits – 2 Stroke Off-Road
Bore and plate to a forged piston with head and power valves modifications includes top end gasket with bearing.

YZ 250 Most Years 265cc $525
For years this size motor was the biggest you could to without custom pistons. Easy to build and inexpensive to rebuild. The pistons are final bore sizes and with Nikasil plating, they can be rebuilt should you have to do so. Power comes on in the bottom and mid ranges for the trail and riders wanting the bottom end. Or we can do port work to make it have a more mid and high-end if you desire. Just tell us what kind of riding you doing. So from desert to trails, this is an easy inexpensive choice. Cylinders are Nikasiled or if you have a Sleeve we can bore and hone to size. Head and Power Valve modification with Top End gaskets and Wrist Pin Beaning are included.

YZ 250 1992-1998 300cc $699
What can we say about these old dogs but there fun to ride! This kit comes with a 74mm custom forged piston that is bored and plated to your cylinder. Head and Power Valve modification along with Top End gaskets and Bearing are all included. If you want the most power out of an old horse this it the way to go!

YZ 250 1999-2016 293cc $649
This YZ kit is newer because 72mm pistons are available from Wiseco and Wossner as a stock part. Your cylinder is bored and Nikailed plated to a 72mm piston. Head and Power Valves modification along with top-end Gaskets and Bearing are included. As always let us know what kind of riding you doing so we can port time it for you

YZ 250 1999-2016 301cc $699
Our biggest YZ kit! The 301 is a 73mm custom-made forged piston with some added adjustments. If you’re looking to outrun the 450s this is the one you want. We are currently racing this in CA in some enduro desert 6, 8, and 24hr races. Our 301 motor gives the all-around power that goes with the territory. Check out on Instagram at Kustom Kraft Performance or follow wade_316.

Your cylinder is bored and Nikasiled to a 73mm piston. Head and Power Valves along with Top End Gasket and Bearing are included in this kit. If you can’t run with the big dogs you have to stay on the porch.

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