ATHENA Top End Gasket Kit for TM RACING EN 300, MX 300 2019-2026

The ATHENA P400465600016 top end gasket kit is designed for TM RACING EN 300, MX 300 from 2019 to 2026. The top end gasket kit brings together the gaskets to replace every time the cylinder head or cylinder comes off. A gasket crushed by tightening never gets its shape back: refitting it means risking a compression, coolant or oil leak, and having to strip everything down again.

Key features

• Head, base and exhaust gaskets, O-rings and washers, depending on the model.
• Laser cutting and surface treatments for consistent sealing.
• Designed by Athena, an OEM supplier, and validated on test benches.

Specifications

• Brand: ATHENA
• Manufacturer part number: P400465600016
• EAN code: 8056216246444
• Weight: 60 g
• Engine: 2-stroke

When to replace it?

• Coolant or oil seeping at the head/cylinder or cylinder/crankcase joint.
• Coolant level dropping, bubbles in the radiator.
• Hissing or black marks where the exhaust leaves the cylinder.

At every piston change and every time the cylinder head or cylinder is removed, even for a simple inspection. Gaskets cost little compared with the work of stripping the engine.

Fitting tips

1. Clean the gasket faces without scratching them (plastic scraper, solvent): they must be clean, dry and free of burrs.
2. Fit the gaskets dry, without sealant, unless the workshop manual says otherwise.
3. Refit a base gasket of the same thickness as the old one, unless you are deliberately adjusting the squish.
4. Tighten the cylinder head in a criss-cross pattern, in several stages, up to the manufacturer's torque.
5. While it's apart, replace the spark plug and refill the coolant.
6. After break-in, check the torque with the engine cold and make sure there are no leaks.

Why ATHENA?

Athena, an Italian company founded in 1973 near Vicenza, designs gaskets, pistons and cylinder kits for motorcycles. An OEM supplier to KTM, Ducati, Fantic, Piaggio and Triumph and a partner of the MXGP world championship, it develops its parts on the test bench and on the track with racing teams.

Spare parts and items to plan

• Piston : WOSSNER 8213D · WOSSNER 8295D
• Piston rings : VERTEX 53010007200 · VERTEX 53010007200N8
• Coolant : MOTUL 1 L · MOTUL 20 L
• 2-stroke oil : LIQUI MOLY 1 L · LIQUI MOLY 4 L

Frequently asked questions

What does the kit contain?
Depending on the model: head gasket, base gasket, exhaust gasket, O-rings and washers. Compare with your original gaskets if you're unsure.

Should I replace it along with the piston?
Yes: as soon as the cylinder head and cylinder are off, new gaskets go back on. It's the right time to fit a new piston kit and new rings if the engine has some hours on it.

Compatibility

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

Fits:
TM RACING EN 300 2026
TM RACING EN 300 2025
TM RACING EN 300 2024
TM RACING EN 300 2023
TM RACING EN 300 2022
TM RACING EN 300 2021
TM RACING EN 300 2020
TM RACING EN 300 2019
TM RACING MX 300 2026
TM RACING MX 300 2025
TM RACING MX 300 2024
TM RACING MX 300 2023
TM RACING MX 300 2022
TM RACING MX 300 2021
TM RACING MX 300 2020
TM RACING MX 300 2019