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Klapton V4
Posted: Sat Jun 20, 2026 9:58 am
by Vincent.vanGinneke
Not a Ariel so not in the for sale section,
Seen this on Dutch Marktplaats.
If you want to stick out between all those who have the new Norton V4 this could be it
Klapton, custom-built 4-cylinder with heads from a Norton 850 on one crankcase.
With modified crankshafts.
Custom-built frame with number.
Also many Triumph parts.
No registration,
no ABS.
1620 cc
yes, it is for sale, wonder if one could get a road licence for it, perhaps that could prove to be a problem in the EU...
https://www.marktplaats.nl/v/motoren/mo ... norton-850
Re: Klapton V4
Posted: Sat Jun 20, 2026 10:45 am
by Julian Murphy

Urgh. Thats a brute.
Re: Klapton V4
Posted: Sat Jun 20, 2026 10:06 pm
by Bob.Murphy
One has to admire the engineering and dedication in producing a 'Mad Max' machine like this.
But only it's mother could love it

.
Bob.
Re: Klapton V4
Posted: Sun Jun 21, 2026 3:59 am
by nevhunter
I can't see how it's a SINGLE crankshaft. Looks heath-robinson to me.
Re: Klapton V4
Posted: Sun Jun 21, 2026 6:48 am
by adrie.degraaff
I think it's a square four.
Re: Klapton V4
Posted: Sun Jun 21, 2026 8:18 am
by nevhunter
What British motorcycle gearbox would take two Commandos power through it? It's also a bit too Long to steer well. How are the Cranks coupled? Nev
Re: Klapton V4
Posted: Sun Jun 21, 2026 8:34 am
by adrie.degraaff
The cranks must be connected the square four way.
What can you do with it? if the engine is running wel i would put it in a 50 year old car, threewheeler or buggy, no mot needed.
Re: Klapton V4
Posted: Sun Jun 21, 2026 9:08 am
by adrie.degraaff
There are more builds coming forsale, some have papers if they where using a standard frame.
Here the BSA-Heemskerk v twin and others.
https://amklassiek.nl/een-motorfiets-ma ... 024/08/24/
Re: Klapton V4
Posted: Mon Jun 22, 2026 7:31 am
by david.anderson
Coupled as a square 4. Counter rotating cranks yes but the drive side is not connected to the timing side of the engine external to the crankcase. The single crankcase has not been widened to fit coupling gears and I cannot see how coupling gears could be fitted inside standard width crankcases unless the central flywheels incorporate coupling gear teeth as per the original square 4 design. The commando crank is a bolt up crank with either side bolting to the central flywheel.
It is clearly not external coupling, so the design must be as per the original square 4 design with central coupling gears.
The size of 2 850s which are 828cc¬¬¬¬¬ each would be 1656cc, not the 1620 stated unless the stroke has been reduced a little, but not likely.
The clutch looks larger than a commando clutch. The gearbox is not Norton but could it be Harley
Strange place to mount the rear brake master cylinder.
Carburetion may not be good. Nortons do not respond well to a single carb per head, and a 90 degree bend would further upset things.
The frame has an incredible number of bends
David
Re: Klapton V4
Posted: Mon Jun 22, 2026 9:17 am
by nevhunter
I don't know how the rear motor would cool either . That layout of motor would be better to be Liquid cooled.. Norton Commando's had trouble with the Inlet rockershafts working in the Alloy Head. Near Impossible to fix. IF the Crank pins are changed from 360 the the single port on the inlet will work very Poorly . Dog knows how much stress is in the crankcases. Could be 120 HP there. Commandos tune well.. Nev