Hepolite Piston Set +.040 Oversize – Norton Commando 850cc (06-4042 / 19342)

Keep your Norton Commando 850 engine running like new with this genuine Hepolite Piston Set, +.040″ oversize — the classic British-made replacement for 850cc Commando cylinders bored to the second oversize. Manufactured by AE (Associated Engineering) under the legendary Hepolite brand name, these pistons were the original equipment specification for the Norton factory and remain the gold standard for Commando engine rebuilds.

This is the correct choice when your cylinders have already been bored beyond +.020″ and require the second oversize at 78.00mm (+.040″). Each matched pair is cast to exacting tolerances and is supplied complete with rings, gudgeon pins, and circlips — everything needed for a full piston installation.

What’s Included

• Two (2) matched Hepolite cast pistons
• Piston rings (complete set)
• Gudgeon pins (wrist pins)
• Circlips

Specifications

• Part Number: 06-4042 / 064042
• Hepolite Number: 19342
• Oversize: +.040″ (78.00mm bore)
• Original Bore Size: 77mm (3.3015″)
• Compression Ratio: 8.5:1
• Construction: Cast
• Quantity: Pair (2 pistons)
• Fits: Norton Commando 850cc (1973–1977)

Compatibility

These Hepolite pistons fit all Norton Commando 850cc models including:

• Norton Commando 850 Roadster (1973–1977)
• Norton Commando 850 Interstate (1973–1977)
• Norton Commando 850 Mk2 / Mk2A / Mk3
• Norton Commando 850 Hi-Rider (1973–1974)
• Norton Commando 850 John Player Replica (1973–1975)

Important: These are +.040″ oversize pistons. Your cylinders must be bored to 78.00mm before fitting. If your cylinders are at standard or first oversize (.020″), see our +.020″ piston set (06-4041) instead.

Sourced directly from Norvil Motorcycle Co. in the UK — the world’s leading supplier of Norton Commando spare parts — and sold exclusively in the United States by Fair Spares New England, your trusted Norvil distributor for New England and beyond.