One of the more rewarding experiences in motocross - off the track - is the maintenance and upkeep of your bike. Wrenching around on your bike is a great way to understand the mechanics of the engine parts as well as introduce you to more of the Do-It-Yourself aspect of the sport.
A popular bike many riders like to upgrade or rebuild is the Honda CR125. This is a peppy little bike from the box but in time, you can add solid aftermarket parts that really crank on the track or trail. There are two ways to go about rebuilding your Honda CR125 - a top end re-build or a bottom end rebuild.
For this guide, it is assumed you already know the set-up and the ins-and-outs of the mechanical side to replacing parts so the focus centers on what's needed to rebuild the top end of your bike - consider this basic maintenance parts to keep your CR125 on the track and you first at the finish line. For a helpful "How-to guide" see How To Rebuild a 2-Stroke Top End.
The top end involves the pistons/rings and all of the replaceable parts above the base gasket. It's time to rebuild the top of your Honda CR125 once the parts reach their service life or are simply worn out. Service life depends on a variety of factors including how hard you ride, the bike's age, and the quality of parts, among other things. The parts listed below work exceptionally well on the Honda CR125. Typically, you'll need to rebuild the top end of your ride about every 10-30 riding hours.
The easiest and most convenient method to a rebuild is to get a Complete Top End set which includes everything you need to replace the top end of your bike in one convenient package. The other route is to purchase your pistons and rings individually which some riders and mechanics prefer. This guide covers both applications.
One bit of information you should know is cast vs. forged pistons. OEM manufacturers all spec cast pistons for their 2-stroke bikes because they perform better in most situations. A forged piston generally provides a longer life span.
Complete Top End Kits for the Honda CR125
Buying parts individually of course gives you more flexibility especially if you prefer a specific brand or running OEM parts. Just remember, when buying a piston don't forget the gasket and you'll also need a wrist pin bearing. The following pistons are the individual pistons sold separately from the Complete Top End Kits.
Like we said - don't forget the gaskets! The Cometic Gasket Kit is the only one we carry for the Honda CR125 and the aftermarket brand we recommend.
Written By: AndrewT