VHM Cylinder Head Insert ref. AE32337-021 for HUSQVARNA TC 250, KTM SX 250 and GAS GAS MC 250 2023-2026

The VHM cylinder head insert is designed for KTM SX 250, HUSQVARNA TC 250 and GAS GAS MC 250 from 2023 to 2026. The insert forms the combustion chamber of the VHM head. Its volume sets the engine's compression: a small volume gives more bottom end and mid-range, a larger volume keeps the engine smoother and longer-revving.

Key features

• Each version shows its three key figures: chamber volume, piston height and squish.
• Change the compression without machining the head, to suit the fuel and the terrain.
• Part number engraved on the insert.
• Fits VHM cylinder heads only.

Specifications

• Brand: VHM
• Manufacturer part numbers: AE32337-021, AE32337-B, AE32337-022, AE32337-C, AE32337-023, AE32337-D, AE32337-E, AE32337-025, AE32337-F, AE32337-026, AE32337-G
• Available versions: Version 021 (21 cc): ref. AE32337-021; Version B (21 cc): ref. AE32337-B; Version 022 (21.40 cc): ref. AE32337-022; Version C (21.40 cc): ref. AE32337-C; Version 023 (21.80 cc): ref. AE32337-023; Version D (21.80 cc): ref. AE32337-D; Version E (22.20 cc): ref. AE32337-E; Version 025 (22.60 cc): ref. AE32337-025; Version F (22.60 cc): ref. AE32337-F; Version 026 (23 cc): ref. AE32337-026; Version G (23 cc): ref. AE32337-G
• Engine: 2-stroke

Choosing the right version

Each version is defined by three dimensions: the chamber volume in cm³ (spark plug hole included), the piston height at top dead centre relative to the top of the cylinder (“−0.55”: piston 0.55 mm below the cylinder face) and the squish, the minimum gap between piston and insert. A smaller volume raises compression: more bottom end and mid-range, but a higher-octane fuel may become necessary.

When to change the insert?

• Switch to a different fuel (98 or race fuel with a higher octane rating).
• Engine knocking (pinking) or running hot: compression too high for the fuel.
• You want more torque on tight or sandy terrain.

Change the insert when you change fuel or type of riding, or if the engine pinks. The insert's three dimensions (volume, piston height, squish) must match your engine.

Fitting tips

1. The insert is changed with the cylinder head removed.
2. Check that the actual height of your piston at top dead centre matches the figure given for the insert.
3. Replace the VHM head O-rings every time you take it apart.
4. Check the squish with solder wire before riding.
5. Tighten the head to the recommended torque, in a criss-cross pattern and in several stages, then fit a new spark plug.

Why VHM?

Founded in 1995, VHM specialises in racing engine parts for motocross, road racing and karting. The brand started out with cylinder heads featuring interchangeable combustion chambers, which became its speciality, and then developed crankshafts, connecting rods and gasket kits.

Spare parts and items to plan

• VHM head O-rings : VHM SK33000.VITON · VHM SK33000
• Spark plug : NGK 3035 · NGK 2305
• Coolant : LIQUI MOLY 1 L · TWIN AIR

Frequently asked questions

Will it fit my original cylinder head?
No: VHM inserts only fit VHM cylinder heads.

Which version should I choose?
Choose according to your engine and fuel. Version 021 (21 cc): 21.00 cc, piston height +0.50 mm, squish 1.60 mm; Version B (21 cc): 21.00 cc, piston height +3.70 mm, squish 1.60 mm; Version 022 (21.40 cc): 21.40 cc, piston height +0.50 mm, squish 1.60 mm; Version C (21.40 cc): 21.40 cc, piston height +3.70 mm, squish 1.60 mm; Version 023 (21.80 cc): 21.80 cc, piston height +0.50 mm, squish 1.60 mm; Version D (21.80 cc): 21.80 cc, piston height +3.70 mm, squish 1.60 mm; Version E (22.20 cc): 22.20 cc, piston height +3.70 mm, squish 1.60 mm; Version 025 (22.60 cc): 22.60 cc, piston height +0.50 mm, squish 1.60 mm; Version F (22.60 cc): 22.60 cc, piston height +3.70 mm, squish 1.60 mm; Version 026 (23 cc): 23.00 cc, piston height +0.50 mm, squish 1.60 mm; Version G (23 cc): 23.00 cc, piston height +3.70 mm, squish 1.60 mm.

Compatibility

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

Fits:
GAS GAS MC 250 2026
GAS GAS MC 250 2025
GAS GAS MC 250 2024
HUSQVARNA TC 250 2026
HUSQVARNA TC 250 2025
HUSQVARNA TC 250 2024
HUSQVARNA TC 250 2023
KTM SX 250 2026
KTM SX 250 2025
KTM SX 250 2024
KTM SX 250 2023