To Start Engine

  1. Partly open throttle by means of hand lever on steering column.
  2. See that petrol is turned on.
  3. Crank engine round about four or five turns.
  4. Switch on magneto and coil ignitions, making sure that the ignition lever is retarded as far as possible.
  5. The engine should then start up by itself as soon as the coil ignition is switched on.
  6. Advance ignition and switch off coil.

If the engine has not been run for a long while, or the petrol has been turned off, the carburettor should be slightly flooded by raising the needle valve in the float chamber.

If the float chamber of carburettor floods, look to the following probable causes:

  1. The float may have been punctured and become totally or partially filled with fuel, and therefore incapable of lifting the toggles which operate the needle valve to shut off the petrol.
  2. There may be a little grit under the needle valve. This can be removed by raising the needle valve off its seat, thus allowing the fuel to flood through and wash away the obstruction.
  3. The needle valve may require grinding in, which should be carefully done, great care being taken, when grinding, to see that there is no grit on the seating or it will be ruined. The best grinding medium for this is jeweller’s rouge or Globe polish. Emery must on no account be used.

Petrol will not feed to the Carburettor

  1. Disconnect filter bowl, turn on petrol, and see that there is a plentiful supply. Should the filter appear starved, disconnect pipe feeding the filter and note if there is a plentiful supply here. If the supply is all in order, then the stoppage is actually in the filter itself – not an uncommon occurrence.
  2. Should there be a poor supply of petrol feeding the filter, it next remains to disconnect the pipe – tank to filter – entirely, and thoroughly cleanse; at the same time check tap on petrol tank, and make certain there is no obstruction here. A petrol tap is just as likely to choke, in fact, more likely, as the petrol feed starts from here. Should everything appear in order, then the next point to receive attention is the feed from filter to the carburettor.
  3. When starting to replace petrol feed system, always start at the tank end, and note as you go along that the petrol feeds freely through each pipe.

Popping in Carburettor

  1. Failure to turn on heating tap.
  2. Opening throttle suddenly before engine is thoroughly warmed up.
  3. Ignition too far retarded.
  4. Valve spring broken.
  5. Tappets adjusted too close, preventing valve from seating.
  6. Petrol supply to carburettor choked.
  7. Petrol jet choked,
  8. Water in petrol.

Stoppage of Vehicle or Engine on the road may be due to :

  1. Petrol supply choked.
  2. Switch accidentally knocked “Off.”
  3. Petrol tap jolted closed.
  4. Petrol too low in tank.
  5. Over-heating through lack of lubrication to the various bearings.
  6. Brakes adjusted too tight.
  7. Bell-crank of contact-breaker seized in fibre bush, see “Contact-Breaker”-Magneto notes, page 13.

Engine will not start

If the petrol Feeds to the float chamber satisfactorily and engine will not start, it may be due to:

  1. Choked petrol jet.
  2. Throttle insufficiently open.
  3. Coil Ignition not working.
  4. Switch not being on.
  5. Throttle too far open.
  6. Sparking plug points too far apart. See notes under “IGNITION.”

Engine will not accelerate

This may be due to:

  1. Ignition being too far retarded.
  2. Contact-breaker points of magneto dirty and out of adjustment. See note under “IGNITION.”
  3. One or more sparking plugs missing fire. This should be checked occasionally; to do this, start engine and open compression taps alternately, accelerate engine and note there is no break in the succession of explosions.

Explosions in Silencer

This is probably due to faulty ignition. Check firing.


  1. Insufficient water in radiator.
  2. Fan belt loose.
  3. Unnecessary running of machine on the lower gears.
  4. Engine short of oil.
  5. Tappets badly adjusted, not allowing valves to close.
  6. Ignition too far retarded.
  7. Clutch slipping.
  8. Carburation difficulties, mixture probably being too strong.
  9. Misfiring.
  10. Petrol too hot from water jacket.
  11. Water circulation at fault.

Engine knocking

  1. Ignition too far advanced. If ignition has been retarded and knocking still continues, it may be due to pre-ignition. In other words, the carbon deposit requires cleaning off the piston heads. Sometimes an engine will fail to stop when ignition has been switched off. This Is also due to pre-ignition or self-ignition through over-heated sparking plug points.
  2. Connecting rod or shaft bearings may be worn.
  3. Missing fire on one or more cylinders.