METEOR Piston Kit for APRILIA RX 50 1980-2000

The METEOR piston kit (Ø 40.3 to 41 mm depending on the size class) is designed for APRILIA RX 50 from 1980 to 2000. The piston takes the pressure of every combustion and passes it on to the connecting rod, thousands of times a minute. Over the hours it wears, its rings stop sealing properly and the engine loses compression: it starts less easily, pulls less hard and runs hotter.

Key features

• Italian piston manufacturer since 1952.
• Complete kit: piston, ring(s), pin and circlips.

Specifications

• Brand: METEOR
• Manufacturer part numbers: PC1538A, PC1538B, PC1538C, PC1538D
• Rings: 2
• Piston diameter: A = 40.3 mm, B = 40.5 mm, C = 40.8 mm, D = 41 mm
• Available versions: A: ref. PC1538A; B: ref. PC1538B; C: ref. PC1538C; D: ref. PC1538D
• 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 METEOR?

A piston manufacturer since 1952, Italy's Meteor has supplied original equipment to manufacturers such as Piaggio and Innocenti. Its Meteor Racing division designs pistons for racing engines, both two-stroke and four-stroke.

Spare parts and items to plan

• Top-end gasket kit : see the selection
• Small end needle bearing : ATHENA
• Spark plug : NGK 3961 · NGK 5722
• Coolant : LIQUI MOLY 1 L · TWIN AIR
• 2-stroke oil : LIQUI MOLY 1 L · MOTUL 1 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: A, B, C, D correspond to different actual diameters (40.3 to 41 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:
APRILIA RX 50 2000
APRILIA RX 50 1999
APRILIA RX 50 1998
APRILIA RX 50 1997
APRILIA RX 50 1996
APRILIA RX 50 1995
APRILIA RX 50 1994
APRILIA RX 50 1993
APRILIA RX 50 1992
APRILIA RX 50 1991
APRILIA RX 50 1990
APRILIA RX 50 1989
APRILIA RX 50 1988
APRILIA RX 50 1987
APRILIA RX 50 1986
APRILIA RX 50 1985
APRILIA RX 50 1984
APRILIA RX 50 1983
APRILIA RX 50 1982
APRILIA RX 50 1981
APRILIA RX 50 1980