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30 JULY 2017

After browsing this website....


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:

g50   small_Matchless G50 053

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

g50b   g50vee

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:

arthureengin010_zpsae9b675b   arthureengin007_zpsed84a0af arthureengin002_zps165c0c26

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

arthureengin017_zps676d769c arthureengin014_zps7964714b

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.


_1485820157_resized_v2_re_graham_white   da937c3d36a5a0d434feb1ec7ad3f13a--gn-aero gnspecial -1 6.2litregn

6.2 litre GN special using aircraft cylinders and heads


SH_GN-SPIDER-ENGINE-CLOSE-UP-1200x800   07d0e1e77f8a02b4f8d50917c8b58e28--car-engine-motorcycle-engine

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:

IMG-20170422-00305   IMG-20170422-00303 IMG-20170422-00306


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!

17103558_273631549734633_6218791337166113159_n   17103391_273632049734583_708630292895128985_n 17021977_273631626401292_345767619676774575_n 16998973_273631559734632_4069710608593845274_n 16998922_273631556401299_9111949230654639289_n 16939222_273631553067966_4493355615105797836_n



A Martinsyde pictured at the Stafford Show (April 2017)



Another DTZ JAP (1323 cc) with Panhard cylinders and heads (all one piece) - a 1950s French car. The stud spacing is the same. Photo: Graeme Gullick.


19 JUNE 2017


JAP 750 in an Ariel Square Four frame, made by Darryl ... and Darryl's 1960's Honda boat engine (currently for sale):

IMG-20170604-00342 IMG-20170604-00343 IMG-20170604-00344

IMG-20170604-00347 IMG-20170604-00345


Triumph RR 750 v-twin 1930-1933 (MAG motor), made in Germany

twnIE-61207_W   twn-po04-33 Triumph-twn-350-1

triumph_rr_750_v2 triumph_rr_750_v2_1931 rr750

  rr750-1 rr image


Montgomery - very rare:

  17758322_1902988566656069_1913306449508300338_o 17758229_1902988543322738_1851225365317247062_o


More Brough-Norton pictures (Matchless MX2 engine in a Wideline Featherbed) Thanks to Rowan Goodefellow DeBonnaire:

  14241556_10210755254457943_5021273515196088868_o 14188366_10210755252097884_1216131575554718165_o

14207811_10210755251337865_6758499329568896081_o 14206220_10210755251017857_3782469385826458241_o 14249904_10210755251857878_8801629310031755413_o


OEC with JAP 750 engine



The RR 1150 (Rough Of Rämsöö) made in Finland by Jouni Ruohola. An imitation of a late thirties Brough Superior, with a supercharger.

18619914_1016655228469281_6165432324612721759_n   18671134_1016655101802627_7301816211029197426_n



Tim Cameron (Ewan's dad) with his Norton-JAP

  1486075_1394026300850847_1159144598_o 1506290_1394026170850860_836331885_o 1602179_1394026354184175_1904800612_o



More Norton-JAPs:

11070088_10152917711383520_8328055026513781020_n   17359115_659834004204034_4320742223995871760_o 14434844_578156869038415_5764914117279732342_o


Another Howard rotary hoe engine project. This one is boardtrack style:

howard4   howard6 howard6

howard1 howard2   howard7 howard5

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