Villiers Technical Information:

4 Stroke Engines

Mark 10

Bore 50mm
Stroke 50mm
Capacity 98cc
BHP Mk 10 1.0 hp @ 2000rpm
BHP Mk 10 HS 1.6 hp @ 3400rpm
Tappet Clearance - Inlet and Exhaust Minimun .006in
  Maximum .012in
Points Clearance .012in / .016in

Mark 12

Bore 55mm
Stroke 50mm
Capacity 120cc
BHP Mk 12 1.2 hp @ 2000rpm
BHP Mk 12 HS 1.95 hp @ 3400rpm
Tappet Clearance - Inlet and Exhaust Minimun .006in
  Maximum .012in
Points Clearance .012in / .016in

Mark 15

Bore 63mm
Stroke 47mm
Capacity 147cc
BHP Mk 15 2.3 hp @ 3000rpm
   
Tappet Clearance - Inlet .003in

- Exhaust

.006in
Points Clearance .012in / .015in

Mark 20

Bore 63mm
Stroke 66.7mm
Capacity 206.5cc
BHP Mk 20 2.5 hp @ 2500rpm
BHP Mk 20 HS 2.7 hp @ 3000rpm
Tappet Clearance - Inlet and Exhaust Minimun .006in
  Maximum .010in
Points Clearance .012in / .016in

Mark 25

Bore 70mm
Stroke 66.7mm
Capacity 256.5cc
BHP Mk 25 3.0 hp @ 2500rpm
BHP Mk 25 HS 3.4 hp @ 3000rpm
Tappet Clearance - Inlet and Exhaust Minimun .006in
  Maximum .010in
Points Clearance .012in / .016in

 

Timing a Villiers Engine

The magneto is timed so that the contact breaker points commence to open when the piston is 3/16" before top dead centre. A rough check on the position may be made without removing the cylinder head, by observing the position of the keyway on the driving shaft when the points are just opening. The keyway should then be 27deg before top. Accurate timing can only be done with the piston visible