VERTEX Piston Kit for SUZUKI RM 85 2002-2024

On SUZUKI RM 85 from 2002 to 2024, the VERTEX piston kit (Ø 51.95 to 52.95 mm depending on the size class) fits in place of the original part. At the heart of the top end, the piston soaks up the heat and pressure of every explosion. As it wears, the rings no longer seal against the cylinder: compression drops, power drops with it, and the risk of seizure goes up.

Specifications

• Brand: VERTEX
• Manufacturer part numbers: 3205400, 3205500
• Compression height: 27 mm
• Piston pin diameter: 14 mm
• Rings: 1 x 1 mm
• Piston diameter: 51.95 mm = 51.95 mm, 52.95 mm = 52.95 mm
• Available versions: 51.95 mm: ref. 3205400; 52.95 mm: ref. 3205500
• Engine: 2-stroke

Choosing the right size class

The letters A, B, C… are very close diameter grades, one hundredth of a millimetre apart. Measure the cylinder bore with a bore gauge (diameter, ovality and taper) and choose the grade that gives the piston-to-cylinder clearance specified by the manufacturer. As a rule, grade A goes into a new or reconditioned cylinder, grade B into a cylinder that has already been run in. A scored or out-of-spec cylinder has to be reconditioned: you don't make up for its wear with a bigger grade.

When to replace it?

• Loss of power, sluggish pick-up, harder starting: compression is dropping.
• Piston slap on a cold engine, getting more and more noticeable.
• On teardown: vertical scoring on the skirt, stuck or worn rings, thick carbon on the crown.

Replace the piston as set out in your bike's service manual, sooner if you race, and straight away as soon as these symptoms appear. As a Cross-Mania guideline, plan for a new piston every 15 to 30 hours of engine running depending on whether you race or ride for fun. Always measure the cylinder at the same time: a new piston in an oval cylinder won't last.

Fitting tips

1. Clean the cylinder and check it: diameter, ovality, taper and condition of the bore coating.
2. Check the end gap of each ring in the cylinder against the figures in the manual or the manufacturer's instructions.
3. Fit the rings with the mark facing up and each gap correctly located on its locating pin.
4. Check the small-end needle bearing and the pin: at the slightest play, tight spot or marked needle, replace the bearing.
5. Fit the piston with its arrow pointing to the exhaust side, oil the pin and the small end, then fit the circlips without distorting them, gap opposite the notch. A circlip that has been taken out is replaced with new piston pin circlips, never refitted.
6. Reassemble with a new top end gasket kit and tighten the cylinder head in a criss-cross pattern to the manufacturer's torque.
7. Refill the coolant and fit a new spark plug.
8. Break the engine in: warm it up gently, vary the revs and avoid sustained full throttle for the first hour.

Why VERTEX?

Founded in Italy in 1953 as a workshop making parts for agricultural engines, Vertex now makes its entire production in Cadelbosco Sopra, near Reggio Emilia, on CNC machines. Since 1996 Vertex has been KTM's official original-equipment piston supplier: its pistons are fitted as standard to many KTM, Husqvarna and GasGas bikes.

Spare parts and items to plan

• Piston rings : PROX · WOSSNER
• Piston pin : WOSSNER
• Piston pin clips : WISECO 125 L
• Top-end gasket kit : PROX · MOOSE
• Small end needle bearing : ATHENA · NTN
• Spark plug : NGK 6801 · NGK 4832
• Coolant : LIQUI MOLY 1 L · TWIN AIR
• 2-stroke oil : LIQUI MOLY 1 L · LIQUI MOLY 4 L

Frequently asked questions

Does the kit include the gaskets?
No: the kit contains the piston, rings, pin and circlips. Add a top end gasket kit, because a head or base gasket can never be reused.

Which size should I order?
Measure your cylinder: 51.95 mm, 52.95 mm correspond to different actual diameters (51.95 to 52.95 mm). Choose the class that gives the piston-to-cylinder clearance specified by the manufacturer.

Can I replace just the rings later?
Yes, as long as the piston and cylinder are still within tolerance. Replacement rings can be ordered on their own, as can the piston pin and the circlips.

Should I replace the small-end needle bearing?
It isn't included. Check it at every piston change and replace the needle bearing at the slightest play or tight spot.

Compatibility

Check the exact model and year of your bike in the list below before ordering.

Fits:
SUZUKI RM 85 2024
SUZUKI RM 85 2023
SUZUKI RM 85 2022
SUZUKI RM 85 2021
SUZUKI RM 85 2020
SUZUKI RM 85 2019
SUZUKI RM 85 2018
SUZUKI RM 85 2017
SUZUKI RM 85 2016
SUZUKI RM 85 2015
SUZUKI RM 85 2014
SUZUKI RM 85 2013
SUZUKI RM 85 2012
SUZUKI RM 85 2011
SUZUKI RM 85 2010
SUZUKI RM 85 2009
SUZUKI RM 85 2008
SUZUKI RM 85 2007
SUZUKI RM 85 2006
SUZUKI RM 85 2005
SUZUKI RM 85 2004
SUZUKI RM 85 2003
SUZUKI RM 85 2002