Jap engine


New Forum Website User
Non-VOC Member
Hello. I have old J.A.P racing engine.
It is 600 cc ohv-model,year 1930.
Someone told me that old Vincent-hrd motorcycles may have use this kind of engine.
Does anyone have better information ?



Well Known and Active Forum Website User
VOC Member
I know a 600cc "UOR" engine was listed as available for HRD's in 1926, but if any were acturally built and sold is beyond me and there were no HRD's in 1930, but it is still possible a Special Vincent-HRD could have been built with a UOR Engine in 1930. Is it a Twin Port or Single Port and can you post a picture of the engine and it's numbers?
Cheers, John

Ian Savage

VOC Vice President
VOC Member
There was at least one 600cc JAP engined pre-A Vincent HRD I'm not sure of the year but it is still irregularly riden in the UK.


New Forum Website User
Non-VOC Member
J.A.P engine is twin port model.
Crankcase number is UOR/W 93864/8
Engine has very big inlet and exhaust valve,almost 50 mm dia.

Has anyone pictures of old H.R.D


Nulli Secundus

Well Known and Active Forum Website User
VOC Member
VOC Forum Moderator
Also look for the following books for pictures of early Vincents (pre Series A)

  • Vincent HRD Gallery - By Roy Harper.
  • Vincent HRD Story - By Roy Harper.
  • PCV The Autobiography of Philip Vincent - Picture of Python (Rudge) engined early Vincent, but same cycle parts to JAP machine.
  • 50 Years Of The Marque - By P C Vincent.
  • Vincent Vee Twins - By Roy Harper.
  • Vincent HRD - By Peter Carrick.
  • Vincent - By Duncan Wherrett.
  • Original Vincent Motorcycle - By J P Bickerstaff - Picture of sv Jap model.
  • Vincent and HRD Motorcycles How They Were Promoted And Sold - By David Wright.
  • Vincent The Complete Story - By David Wright
There may be others out there.