Dart JAP

Unique. Dart JAP V-twin, engine from 1918, frame c1924.

Let’s start with what we know; the facts; from the owner of this machine for the last 60 years. The bike belonged to his Uncle (Arthur served a motor engineer apprenticeship in 1903 and is described as larger than life) and laid derelict in a shed for at least 10 years before it was acquired by the current owner, so that goes back to the mid-forties. The bike had Dart JAP painted in white on a red background on both sides of the tank, just as it has now. A full and exhaustive restoration and rebuild was completed by the engineer-owner between 1984 and 2003 and the result is what you see here. Frame was professionally aligned (the intention was to road register it but that never quite came to fruition), forks overhauled with new pins, bores honed an new rings (genuine JAP new old stock) fitted to the cast iron pistons. Crank journals were reground and new phosphor bronze main and big end bearings made and fitted, along with new gudgeon pins and small end bearings. The gearbox was rebuilt with new bearings. A drip-feed oiler was modified and fitted. The clutch was originally heel-operated and has been modified to operate from the handlebar. The carburettor is an improvement on the original as is the front brake, borrowed from a BSA Bantam. The engine starts easily and runs well, although not road tested. The engine is a JAP 5hp side valve v-twin with a bore and stroke of 70×85 giving 654cc, engine number 8/81223 EX (could be experimental or Excelsior?) which dates it as 1918. Gearbox is a Sturmey Archer 3-speed, number HW 1735. Carburettor is an AMAC needle-less type with two control levers. Magneto is an ML Type CKV50, number A4542.
The frame number is 893 clearly stamped in small numbers on the lower rear frame lug but we have no factory records to refer to on this for dating purposes. Michael Worthington-Williams writes about this bike “I’d say that without doubt your bike was made by Dart Engineering Company of 314A Stony Stanton Road, Coventry”. Dart Engineering were only in business between 1923 and 1924 so we’ll run with that and assume it was an experimental model, which fits with the EX engine number (although that could also indicate it was fitted to an Excelsior). Research, including the owners’ enquiries reveals nothing to contradict this. Indeed, one expert comments in a very old VMCC magazine..”No mention is made of a JAP engine variant, although the frame architecture in the photos is very similar to a magazine image of a Dart Brooklands racer from 1923″. There are a number of photos recording the pre-restorative state of the machine and it’s transformation over 19 years of restoration. An e-mail from Pat Davy dated 06/09/2015 regarding the JAP engine confirms it is of 1918 manufacture and goes on to say…”The picture of the Dart is most useful in confirming the 1918 date as it shows a drop tube frame and SA 3 speed gear box”.
There you have it. Undeniably a very attractive V-twin flat-tanker, full of character and in absolutely excellent mechanical condition. Mr W-W was happy to issue a dating letter in 2003 and we are sure others would today so it could be road-registered and would make a practical vintage machine with chain drive, hand clutch and shortened hand gear-change lever. We would be very interested to hear from anyone who can add anything to the history-gathering exercise with information or thoughts on this unknown model. We would be very interested to hear from anyone who would like to give this fine machine a new home (for the next 60 years?).