PROX Top End Gasket Kit for KTM SXF 350, XCF 350, HUSQVARNA FC 350, FX 350 and GAS GAS EXF 350, MCF 350 2023-2027

On KTM SXF 350, XCF 350, HUSQVARNA FC 350, FX 350 and GAS GAS EXF 350, MCF 350 from 2023 to 2027, the PROX 35.6363 top end gasket kit fits in place of the original part. As soon as the cylinder head or cylinder is removed, their gaskets must be replaced: crushed when tightened, they have taken the shape of the parts and will no longer seal. This kit groups under one part number the gaskets needed to reassemble the top end.

Specifications

• Brand: PROX
• Manufacturer part number: 35.6363
• Weight: 110 g
• Engine: 4-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 PROX?

ProX Racing Parts has been supplying engine and clutch parts to motocross riders since 1975, from its headquarters near Amsterdam. According to its catalogue, most of its parts are made in Japan, by manufacturers that also produce parts for the Japanese motorcycle makers.

Spare parts and items to plan

• Piston : WOSSNER · PROX
• Piston rings : PROX · WOSSNER
• Spark plug : NGK
• Coolant : LIQUI MOLY 1 L · TWIN AIR
• 4-stroke engine oil : LIQUI MOLY 10W40 1 L · MOTUL 10W50

Frequently asked questions

What does the kit contain?
Depends on the model. Compare with your original gaskets if in doubt.

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:
GAS GAS EXF 350 2025
GAS GAS EXF 350 2024
GAS GAS MCF 350 2025
GAS GAS MCF 350 2024
HUSQVARNA FC 350 2027
HUSQVARNA FC 350 2026
HUSQVARNA FC 350 2025
HUSQVARNA FC 350 2024
HUSQVARNA FC 350 2023
HUSQVARNA FX 350 2026
HUSQVARNA FX 350 2025
HUSQVARNA FX 350 2024
HUSQVARNA FX 350 2023
KTM SXF 350 2027
KTM SXF 350 2026
KTM SXF 350 2025
KTM SXF 350 2024
KTM SXF 350 2023
KTM XCF 350 2027
KTM XCF 350 2026
KTM XCF 350 2025
KTM XCF 350 2024
KTM XCF 350 2023