Piston 125

Features

• made in Italy by Meteor – trusted piston specialist since 1952
• premium aluminium alloy – lightweight, strong, and durable
• precision machining ensures perfect fit and consistent performance
• excellent wear resistance extends piston and engine life
• smooth power delivery – reliable performance in trials conditions
• complete kit for easy installation – piston, rings, pin, and circlips included
• available in different piston size codes (A/B/C, etc.) – match with the code stamped on your cylinder for correct fitment

Bike: Gas Gas Pro/Racing/GP 125 02-22 

Size A 53.95MM

Size: B 53.96MM

Most trials motorcycles use pistons available in size codes A, B, C, and sometimes D). These codes represent very small differences in piston diameter – usually only a few hundredths of a millimeter – to match the gradual wear of the cylinder.

From new – your cylinder is stamped with a code (e.g. “A”). The factory installs the matching piston (A).

1. first replacement – you can usually fit another piston of the same code if cylinder wear is minimal
2. next replacement – once the cylinder has worn further, you must move to the next size code (e.g. A → B → C)
3. when all codes are used – the cylinder must be re-plated or replaced to restore proper clearances

Example progression:

• cylinder stamped A → First piston: A → Second piston: B
• cylinder stamped B → First piston: B → Second piston: C
• and so on…

⚠️ Important: Always check the size code stamped on your cylinder before ordering. Using the wrong piston size can cause poor performance, excessive wear, or engine damage.

Dimensions 

• standard diameter – 54mm
• compression – 29.5mm
• head type – barrel head
• head – 2.7mm
• total length – 63.2mm