V-Twin News p.12

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30 JULY 2017

After browsing this website....

WHAT IS YOUR DREAM V-TWIN ENGINE?

My own idea of the ultimate v-twin was to take 2 top ends from the most advanced British single cylinder racing engine, and create a v-twin.... using the top ends of two single overhead camshaft Matchless G50 racers.

Here is the G50 engine:

and here I visualised what the v-twin engine would look like using photoshop:

Then, to my amazement, I found a discussion on the Classic Motorcycle Racing Forum... a retired engineer - Arthus Lewthwaite - has been collecting parts to make a 1000cc 60-degree v-twin with two G50 top ends!

Arthur used to work for AMC (Matchless) in the sixties, and is good friends with Tom Mortimer, the only surviving Matchless race mechanic. In 2013, he started making mock-ups of the crankcases, using original factory drawings of the G50.

Here is Arthur with another of his inventions... a paddock starter:

and here are some pictures of the project in 2013:

...and comparison of the new design v-twin cases and the original single cylinder cases:

The project has moved forward, though slowly over the last 4 years, due to other projects, funds, and health problems. This is how things were going two years ago in 2015:

"…on my G50 twin I am using Mitsubishi 3-litre twin-turbo con-rods with 4 valve pistons from same, using the basic-design head with 4 valves and hydraulic tappets, twin cams in head with single chain drive to each head, with shell bearings in split con-rod, fuel injection, running off a 3 litre fuel injection computer, hopefully, but was designing head to mimic a G50 head from the outside without a bore in the inlet for an injector, so a carb can be fitted instead, (pistons by the way are 92 mm did bore size) so the whole lot looks the same as a standard G50 from the outside.”

In January 2017, Arthur was considering getting Dave Nourish to machine him a one-piece crank (though Dave Nourish is famed for being snowed under and delayed in finishing jobs). He was also looking for Cosworth G50 pistons (maybe just to modify the Mitsubishi ones to their measurements?) I have been in touch with Arthur this week, and he said it will have a "retro-modern-style" roling chassis (Seeley-style frame) with a Porcupine style tank... and he is planning on eventually putting the bikes into production! They may even be built on the Isle of Man!

Here is the 2013 forum post and Here are the pictures

More huge v-twin engines made using Aeroplane barrels and heads... all in GN cyclecars...:

Mark Walker's 1922 GN cyclecar (4.2 litres) with cylinders and heads from aTiger Moth bi-plane.

6.2 litre GN special using aircraft cylinders and heads

GN Spider 2................................................................................................................and another interesting cyclecar v-twin engine.

Another picture of the Japbeam 750:

"Widowmaker" V8 drag-racer:

More on the Shackleford:

I had a chat with Brian Shackleford at the Stafford Show (April 2017) and took these three photographs of his bike, which was on display on the BSA stand:

Here are the brief facts: The frame is BSA; the gearbox is BSA; the crankcases and barrels are Harley Davidson; the heads are BSA B31; the forks are "Reliant"!; There are two sets of points with 22.5 degrees between them; the points are from a Renault 5; the Vee is 45 degrees; camshafts and crankshaft made by Brian. In the second picture below, you can see Brian's Sunbeam, which has lent it's styling to the Shackleford. I am hoping Brian will soon be able to supply a build story for the "A V-Twin Obsession" site, soon. Watch this space!