VERTEX Piston Kit for KTM EXC 144, EXC 150, SX 144, SX 150 2007-2017

On KTM EXC 144, EXC 150, SX 144, SX 150 from 2007 to 2017, the VERTEX 3384400 piston kit (Ø 57.95 mm) 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 number: 3384400
• Compression height: 29.5 mm
• Piston pin diameter: 15 mm
• Rings: 1 x 1 mm
• Piston diameter: 57.95 mm
• Engine: 2-stroke

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 20 to 40 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 : ATHENA · WOSSNER
• Piston pin : VERTEX · WOSSNER
• Top-end gasket kit : ATHENA · PROX
• Small end needle bearing : PROX · NTN
• Spark plug : NGK 2707 · NGK 90908
• Coolant : LIQUI MOLY 1 L · TWIN AIR
• 2-stroke oil : LIQUI MOLY 1 L 3065 · LIQUI MOLY 1 L 3063

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.

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:
KTM EXC 144 2010
KTM EXC 144 2009
KTM EXC 150 2016
KTM EXC 150 2015
KTM EXC 150 2014
KTM EXC 150 2013
KTM EXC 150 2012
KTM EXC 150 2010
KTM EXC 150 2009
KTM SX 144 2017
KTM SX 144 2016
KTM SX 144 2015
KTM SX 144 2014
KTM SX 144 2013
KTM SX 144 2012
KTM SX 144 2011
KTM SX 144 2010
KTM SX 144 2009
KTM SX 144 2008
KTM SX 144 2007
KTM SX 150 2017
KTM SX 150 2016
KTM SX 150 2015
KTM SX 150 2014
KTM SX 150 2013
KTM SX 150 2012
KTM SX 150 2011
KTM SX 150 2010
KTM SX 150 2009
KTM SX 150 2008
KTM SX 150 2007