PROX titanium Exhaust Valve for KAWASAKI KXF 250 2025-2027

On KAWASAKI KXF 250 from 2025 to 2027, the PROX titane 28.4355-1 exhaust valve fits in place of the original part. On a four-stroke, the exhaust valve has gases at several hundred degrees flowing past it on every cycle. A tired valve loses compression and makes hot starts difficult.

Specifications

• Brand: PROX
• Manufacturer part number: 28.4355-1
• Weight: 30 g
• Engine: 4-stroke

When to replace it?

• Valve clearance closing up from one check to the next.
• Hard hot starting, loss of compression.
• Marked valve face or cupped valve when removed.

As soon as the valve clearance no longer holds between two checks. Always replace the valves on the same side together and have the seats recut.

Fitting tips

1. Have the valve seats recut and check the guides.
2. Don't lap a coated titanium valve with grinding paste: it would destroy the coating.
3. Fit new valve stem seals and check the springs.
4. Set the valve clearance with valve shims if needed, then check it again after the first few hours.
5. Refit with a valve cover gasket in good condition.

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

• Valve stem seals : PROX 35.VS021 · PROX P650901/4
• Valve shims : PROX 29.VSA748 · PROX 29.748
• Valve cover gasket : ATHENA S410250015066 · ATHENA S410250015039

Frequently asked questions

Do both valves need replacing?
Yes, exhaust valves are usually replaced as a pair, with the seats recut.

Titanium or steel?
Titanium is much lighter: the valve train copes better with high revs. Steel is more tolerant of wear and is perfectly suited to leisure riding; don't mix the two materials without following the manufacturer's recommendations (springs).

Compatibility

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

Fits:
KAWASAKI KXF 250 2027
KAWASAKI KXF 250 2026
KAWASAKI KXF 250 2025