Forestry Memories

J.A.P. 5 single cylinder engine cutaway drawing and specifications

This is a cutaway drawing of a J.A.P. Model 5 engine; these engines were used by a large range of horticultural and agricultural machine manufacturers and an example appears in image No. 5306 in this archive, powering a Clifford rotary cultivator at the Forestry Commission, Ledmore nursery.

These air cooled JAP engines were manufactured by J.A. Prestwich & Co Ltd, of Tottenham.

Their promotional material claimed that the JAP engines are first in the field for driving all kinds of Agricultural machinery with economy and efficiency.

Just About Perfect – for every power purpose.

Here follows a mechanical specification for this engine:

• Bore 80mm ( 3.15 in )
• Stroke 82mm ( 3.23 in )
• Capacity 412cc ( 25.14 cu in )
• Weight (dry) 55.5kg (122 lb)
• Power rating 4.5 HP @ 2,200 rpm
• Sump Capacity 1.3l (2 pints)
• Ignition Wico Type CJ936 impulse magneto
• Ignition Timing 20* B.T.D.C.
• Carburettor Zenith Type 24T-2 or Amal 379 or Villiers B 1320 ( Also a JAP carb fitted on some earlier engines )
• Sparking Plug Champion L10 , 14mm , 0.20 in gap
• Rotation Anti-clockwise looking at the drive shaft

MY APOLOGIES, THE WEBSITE CANNOT LOAD THIS PDF FILE AT PRESENT!
I have also made available a pdf document of the engine cutaway drawing, along with a list of the service specifications for the engine. The engine is a single cylinder, four stroke, using either petrol or tractor vaporising oil (TVO) fuel.

The drawing and service specifications were taken from my late Dad’s book ‘Farm Mechanisation Handbook’, Tractor and Implement Operation and Repair, by T. Hammond Craddock, Temple Press Ltd, 2nd Edition, completely re-written and published in 1952.

The mechanical specifications were obtained from the “Vintage Pedestrian Tractors” website that displays a comprehensive range of these machines, their images and restoration.

Any further information or comments upon this engine, or its other forestry applications would be welcome.

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Groups: Other Vehicles and Machines, Tractors Ploughs and Drainage Machines

Group: Forestry in Action - 1908 pictures

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