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Engine Modifications

The Bike

Engine Builder

The engine and gearbox have been built wholly by renowned Royal Enfield performance tuner Andy Berry. Andy has restored Royal Enfields since 1978 and has built in excess of 80 engines during that time. Known for his ability to make Royal Enfields, and in particular Bullets, go faster, Andy relished the opportunity to work on my bike to make it more robust for long distance travel. It would be fair to say that Andy is something of a perfectionist when it comes to engines and it is largely down to him that I have so much confidence my 1953 bike will make it to India without any serious mechanical problems. Contact: Email: ajb1962@hotmail.co.uk Tel: (+44) 01772 788077


I decided to use a Hitchcocks performance 500cc crankshaft for several reasons: the flywheels are precision engineered from high quality steel billets with ground bores for the crankpin and main shafts; the crankpin assembly has a far larger diameter into the flywheels and uses a silver plated steel needle caged bearing instead of a Bullet's usual plain metal floating bush big end; the connecting rod is made of forged steel instead of the light alloy used in the 1950s. Although expensive, these crankshafts have proved very durable under race conditions so it seems well worth the cost to use it in a touring engine. Hitchcocks have recently had a batch of these cranks made specially for early English Bullets. However, when Andy built my 1953 engine, the cranks were only available for Indian 500cc alternator type engines. Andy carefully cut the end off the drive side of the mainshaft and rethreaded it to fit.

Cylinder Head

I bought an almost new early British 500cc cylinder head from Royal Enfield enthusiast Mark Mumford at a Royal Enfield Owners Club event. Becoming a member of a classic motorcycle owners association has many advantages and the REOC is a very friendly club. Being able to pick up hard-to-find spares from other members at reasonable prices is a real bonus. First of all, Andy ported the head, then moderately gas flowed it so that there would be some increase in performance without making the engine too radically tuned. He fitted a genuine Woodsman inlet valve and a modern hardened Indian Bullet exhaust valve, which can more easily cope with unleaded petrol. We used Hitchcocks' competition valve springs and Samrat alloy rockers. These rockers are made of light alloy, the arms have a slimmer profile than the Bullet's standard rockers and they are machined for O rings to ensure maximum oil supply. I bought mine when I was last in India, but they are readily available in most countries.

Belt Drive

Belt drive kits for Bullets were developed for racing by the likes of Steve Lynsdell and Bob Newby in the early 1980s. Whatever the riding conditions, there should be no slip or drag. We fitted a Hitchcocks belt drive kit to the 1953 Bullet as we believed it would be more robust than the standard item and easier on my hand if I'm faced with busy city traffic at the end of a long days ride. It also has the added benefit of being maintenance free so I won't need to carry spares or ATF or adjust a slipper tensioner. Andy had never used one in a pre-1956 Bullet with a slim outer chaincase and it took quite some work to make it fit. Andy machined 1/4" off the back of the clutch. This allowed the clutch to sit further down the splines of the gearbox mainshaft. He also machined the edges off the teeth of the clutch drum to allow the clutch to clear the chaincase. At the front pulley it was necessary to machine the spacer at the back down by 3/16" and remove some excess metal from the inside of the outer cover.

Fuel Cat

My motorcycle was originally built to run on leaded 4 Star petrol. To cope with poor quality, low octane unleaded petrol iíve fitted a Fuel Cat. This should help my engine run cooler, protect the exhaust valve and help with power when the fuel is low grade. You just drop it in your petrol tank and forget about it! Contact: Formula Power, The Old Milking Shed, St. John's Green, Nr. Horsham, W. Susses, RH13 7JN Tel: 01403 754173


We used a Hitchcocks English-made forged piston, again going for a top of the range item because it is more likely to survive prolonged tough riding conditions. In pursuit of extra power, we elected to fit a 535cc size. Andy had my barrel (which came off a Big Head Bullet) bored to suit. The piston gives a compression ratio of 9:1, which is too high for my purposes, so we fitted a 2mm alloy compression plate to reduce compression to approximately 8:1.

© 2015 Gordon G. May. All Rights reserved. | info@overlandtoindia.co.uk

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