BIG BORE PISTONS AND GASKETS by PAYPAL

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If you have a PayPal account and also purchased a big bore kit built by Forward Motion and know what parts you need, just enter the model of your bike and click on the boxes for the parts and shipping choice. The order amount is displayed below and when you check out you’ll be prompted for your Paypal details. Forward Motion sends replacement parts from Monday through Saturday by Priority and Express Mail.

Please make sure to enter Bike Make and Model and any notes regarding the piston part number on your bike.

INFO ON BIG BORE PISTONS AND GASKETS

Forward Motion is the online source for big bore piston and gasket kit replacements and next day order fulfillment. We stock a full range of Wiseco catalog and custom Pro-Lite Supermini, GP 144, and 295cc 2-stroke pistons (kits include rings, pin, bearing and clips) for CR,KX,RM,YZ,&CR/WR from the model years of 1990-2011

Forward Motion stocks oversized gasket kits made for bikes with steel head gaskets not o-rings.(Honda CR, and Kawasaki KX, and all 300 kits) Big bore cylinders with head gaskets require oversized gaskets so there’s no contact with the piston.

Forward Motion sells the replacement parts for a complete top end job (piston and gasket kit) or individually; rings, gasket kit, piston kit.

REPLACEMENT PISTON TYPES AND BRANDS

There are 2 types of pistons; catalog and custom. Catalog means you can get it from anywhere and custom means you can only get replacements from the original vendor whom commissioned the piston.

There are types of piston manufacturing methods and materials; cast and forged. Cast pistons can run tighter clearances and handle high thermal loads. Forged pistons are lighter and more durable but noisier.

All of the supermini pistons are only made by Wiseco. With the 58mm 144cc piston kits, you have a choice of 4, both forged and cast. The  250s big bored to 72mm 295cc require Forward Motion’s custom forged & coated piston kit and a special gasket kit.

MX LITES 144cc Pistons and Performance

The 4 piston kits available for the most popular 125s from the past 21 years include Wiseco custom, Wiseco catalog, Vertex, and Wossner. In 1990 Eric Gorr of Forward Motion commissioned the first Wiseco custom forged and coated piston kit. It is a universal kit that fits cylinders converted by Forward Motion, Boyesen Performance, Max-Power, Millennium, Pro-Action, and RPM from 1990 onwards. Forward Motion’s custom forged Wiseco sells for the least at only $120 and features a longer skirt for use on strokers, and lightening reliefs on the inside so the ports can be widened to the max without the threat of blow-off out the exhaust. The coatings to the crown, ring groove, and pin bore are hard anodizing with Teflon for long life.

Wiseco makes a catalog part #846MO5800 for the YZs but it has the same dimensions as FM’s custom Wiseco and fits all the same bikes. The Wiseco GP piston is lightweight, flat top, and has skirt coatings. $155

Vertex is an Italian company that specializes in making cast alloy pistons with high silicon content to handle high thermal loads like experienced in expert mx, dirt track, and shifter karting. The Vertex has a skirt coating and will run a lot quieter with quick start-up than a forged piston. $125

Wossner is a German company that competes with Wiseco, making forged and coated pistons. Their 58mm 144cc piston is a flat top and the lightest of the brands. It is the choice of Yamaha for their GYTR Kit parts for the YZ144. $125

HOW TO DETERMINE IF YOUR BIKE HAS A BIG BORE?

If you purchased a used bike with an unknown mechanical history and not sure what the displacement is, we have a service to identify the correct big bore parts for your engine’s top end. You can tell us the numbers on the center of the piston crown, provide an accurate measurement, or send us the old piston and the top end assembly. We offer free lifetime honing on cylinders that we’ve converted to big bores since 1990.

If your engine was converted to a big bore by a company that went out of business or discontinued the old piston part number, we can update your top end assembly to accept a modern piston that is easy to get online. 

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