PROOTOM adjustable valve shim kit for 450cc motocross bikes — 9.48mm 141-piece (1.20–3.50mm, 0.05mm steps) steel shims

This comprehensive shim kit gives mechanics and home riders the parts they need to service shim-over-bucket valve trains on popular Japanese 450cc motocross and enduro models. It includes three shims per size across the range, enabling precise adjustments without sourcing individual shims. The parts are made of steel, sized to a 9.48mm diameter, and designed to be compatible with CRF450R, CRF450X/RX, YZ450F and WR450F platforms as well as many KXF, KX, KLX, RMZ and YZF variants that use the same shim dimensions.

How does this kit make valve maintenance easier?

The kit eliminates repeated trips to suppliers by providing a full spread of shim thicknesses in 0.05mm increments, so you can achieve the exact clearance required. With three pieces of each thickness, you have spares for rechecks or twin-cylinder applications. The shims are pre-sized for straightforward fitment into shim-over-bucket valve systems.

• 141 pieces cover 1.20–3.50mm in 0.05mm steps
• Three shims per thickness for redundancy
• Steel construction resists wear during installation
• 9.48mm diameter fits common 450cc valve buckets

Will these shims fit my CRF450 or YZ450F engine?

The kit is manufactured to the 9.48mm diameter standard used on many Japan-origin 450F off-road engines. It's intended for CRF450R/X/RX, YZ450F and WR450F models and fits other brands that share the same shim diameter and valve train layout. Always verify your motorcycle’s service manual for recommended shim diameter and clearance ranges before installation.

• Compatibility: CRF450R, CRF450X, CRF450RX, YZ450F, WR450F
• Also fits many KXF, KX, KLX, RMZ, YZF 450 models with 9.48mm shims
• Check service manual for shim-over-bucket specifications
• Not for non-matching diameters or different valve systems

How precise are the shim increments and why that matters?

Shims are supplied in 0.05mm increments, providing fine control over valve clearance adjustments. Smaller increments let you reach the factory-specified clearance without overcompensating, which helps maintain performance and reduces the risk of valve noise or premature wear. The 0.05mm step is standard for accurate valve setting work on high-performance 450cc engines.

• 0.05mm increment sizing for accurate clearance tuning
• Covers 1.20–3.50mm to suit many clearance requirements
• Three items per size allow staged changes and backups
• Better fit helps reduce valve train noise and wear

What’s included and how do I use the kit?

The kit contains 141 steel shims, each 9.48mm in diameter, spanning 1.20mm to 3.50mm. Use a feeler gauge and your motorcycle’s specification sheet to measure current clearances, then select the shim thickness that brings the clearance into spec. Replace the shim-over-bucket shim carefully and recheck clearances after a few heat cycles.

• 141 steel shims total, organized by thickness
• Range: 1.20mm through 3.50mm in 0.05mm steps
• Intended for shim-over-bucket valve configurations
• Use with feeler gauge and service manual measurements

Who is this for: This PROOTOM OTOM valve shim kit is aimed at professional tuners, independent mechanics, and experienced riders who perform valve maintenance on Japanese 450cc off-road engines. It’s useful for anyone who needs a complete set of replacement shims for frequent rebuilds, track-season prep, or to carry as a workshop or race-day spare supply. If your motorcycle uses 9.48mm shim-over-bucket valves and you want precise, incremental adjustment options without sourcing individual sizes, this kit is a practical and cost-effective choice.