Valve shim calculator

Measure the valve clearances with the engine cold and enter the measured clearance and current shim thickness for each valve. The calculator shows whether the clearance is OK and works out the shim that brings it to the middle of the allowed range.

Shims

Shim diameter

Shim thickness step

Number of valves (intake + exhaust)

Allowed valve clearance (mm)

Intake min

Intake max

Exhaust min

Exhaust max

The default values are for KTM SX-F engines – check the clearances for your engine in the service manual.

Intake valve 1

Measured clearance (mm)

Current shim (mm)

New shim: – mm (–)

Clearance with new shim: – mm

Intake valve 2

Measured clearance (mm)

Current shim (mm)

New shim: – mm (–)

Clearance with new shim: – mm

Intake valve 3

Measured clearance (mm)

Current shim (mm)

New shim: – mm (–)

Clearance with new shim: – mm

Exhaust valve 1

Measured clearance (mm)

Current shim (mm)

New shim: – mm (–)

Clearance with new shim: – mm

Exhaust valve 2

Measured clearance (mm)

Current shim (mm)

New shim: – mm (–)

Clearance with new shim: – mm

Exhaust valve 3

Measured clearance (mm)

Current shim (mm)

New shim: – mm (–)

Clearance with new shim: – mm

Results are calculated estimates. Always check your vehicle manufacturer's instructions.

Matching products: Valve Adjustment Washers

How to use

Find the allowed clearance for the intake and exhaust valves in the service manual (e.g. KTM SX-F: intake 0.10–0.15 mm, exhaust 0.12–0.17 mm).
Turn the engine to top dead centre on the compression stroke and measure each clearance with a feeler gauge. The engine must be cold.
Remove the camshaft and measure or read the current shim thickness (the number on the shim, e.g. 2.80 = 2.80 mm).
Enter the values – the calculator works out the new shim. Measure the clearances again after replacing the shims.

Frequently asked questions

How is the new shim thickness calculated?

New shim = current shim + (measured clearance − desired clearance). If the clearance is too small, fit a thinner shim; if it is too large, a thicker one. The result is rounded to the nearest available shim size.

Why does the intake clearance get smaller over time?

The valve and valve seat wear and the valve sinks deeper into the seat, so the clearance gets smaller. If the clearance needs reducing often, the valves may be worn and need replacing.

What happens if the clearance is too small?

The valve may not close fully, the engine starts poorly and the valve can burn. Too large a clearance causes ticking and faster wear.

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