Timing the magneto




Untighten the magneto :

-          - Remove the timing cover,
- Undo the magneto armature nut in the centre of the timing unit. After loosening, the nut will tighten and begin to withdraw the timing unit from the armature.

Insert a small block between the projections of the front plate and the back plate on the timing unit to wedge them apart.

Adjust the contact point gap :

-          - Insert a 3 mm gauge and adjust to get an easy passage, since the actual figure, expressed in inches is slightly larger.
- Check that the 4 mm gauge is too wide. If not, reduce the gap.

Bring the piston to the right timing point, 38 degrees full advance for all models but original MSS (36 degrees).

First one need to carefully find the top dead centre (TDC) with both valves closed :

-          - Remove the spark plug,
- Go close to a TDC. Check it's the right TDC, with closed valves, by turning the engine alternatively and feeling with a finger in front of the spark plug hole that there is some air exhausted,
- Attach a timing disc to the driving side mainshaft and fix a pointer. I personaly use a home made disc which gets close to the dynamo cover fixing pin, which makes a good pointer,
- Go on rotating the engine using a spanner on the dynamo, the belt being well tightened,
- Put a 10 cm long pin in the sparkling plug hole and hold it loose,
- Rotate the engine forwards and backwards to very precisely find the two contact positions between the piston and the pin (which must not move at all),
- Adjust the timing disc to get the same reading at both contact positions. The length of the pin is optimised when the common reading is between 30 and 40 degrees,
- Not holding the disc, rotate the engine to the zero mark on the disc : the engine is just at the TDC,
- Rotate the engine backwards (clockwise) to the 60 degree mark on the disc,
- Now rotate the engine forwards until the disc shows 38 degrees (36 for an original MSS) : the engine is ready for the connection of the magneto.

Get the contact points to the opening position :

-          - Insert a cigarette paper between them when open
- Facing the points, turn the magneto clockwise until contacts close
- Go on turning very slowly while maintaining a light pull on the cigarette paper
- As soon as the paper withdraw from between the points stop moving
Nota : If not well experienced, it's advisable to do the operation several times to confirm the right position. Actual cigarette paper is mandatory.

Refit the automatic timing unit :

-          Tighten the nut on the automatic timing unit while firmly maintaining the points with the left hand. There is very little risk to accidently turn the engine but more to rotate the magneto armature ! If this happens, one need to resume adjusting the point opening with the cigarette paper. At last the engine start to rotate, together with the magneto. Select the second gear and put a foot on the brake pedal. Go on firmly tightening. The automatic timing unit being always at risk of loosening don't hesitate to hardly tighten (stop before breaking something, of course !).


Refit the timing gear cover, at least provisionaly before starting the engine. If not refitted be sure to get oil spread over your parking place several meters away. More dangerous : tappets are not lubricated.

The engine should start at first or second attempt. If not, in addition to the usual advice, and especially after a carburetter overhaul, check the throttle position. If in doubt, slightly open it.




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