PROX Timing Chain for YAMAHA YZF 250 2027

On YAMAHA YZF 250 2027, the PROX 31.2427 timing chain fits in place of the original part. On a four-stroke, the timing chain links the crankshaft to the camshafts. A tired chain gets noisy, upsets the timing and can jump a tooth: with valves hitting the piston, the damage is severe.

Specifications

• Brand: PROX
• Manufacturer part number: 31.2427
• Weight: 200 g
• Engine: 4-stroke

When to replace it?

• Rattling or chain noise on the timing side, especially at idle.
• Tensioner at the end of its travel.
• Timing marks that no longer line up.

At the intervals in the service manual, and as soon as the tensioner reaches the end of its travel. Check the sprockets and the guides at the same time.

Fitting tips

1. Set the engine at top dead centre on the compression stroke, marks aligned, before removing anything.
2. On most motocross engines the chain is endless, with no master link: replacing it means removing the crankshaft sprocket or a camshaft, as described in the manual.
3. Line the camshafts up with their timing marks again, then put the tensioner back under tension.
4. Turn the engine over two full turns by hand and check the timing again before starting.
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

• Cam chain tensioner : GE.CO
• Valve cover gasket : MOOSE 817852MSE · MOOSE 819030MSE
• Valve shims : MOOSE · PROX
• 4-stroke engine oil : MOTUL 10W50 · LIQUI MOLY 10W40 1 L

Frequently asked questions

Should I replace the tensioner?
Check it: a worn tensioner, or one at the end of its travel, must be replaced along with the chain.

Compatibility

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

Fits:
YAMAHA YZF 250 2027