Puch VF/VZ50 setting the timing

Two-stroke timing has to be set right not only for the best performance, but also so the bike will run in the right direction!
The bike manual should specify what the timing should be, it might be specified as a piston distance below top dead centre (TDC) or the number of degrees of crank rotation before TDC.
On the Puch VF/VZ50. The manual states that the spark should occur
0.8mm -> 1.2mm before TDC and the contact gap should be 0.4mm.
The process is simple enough and only slightly difficult because some of the work has to be done through the flywheel.

A process is needed to determine when the piston is 0.8 ->1.2mm below TDC and also determine when the points are just open.

Checking when the points open is a matter of running a continuity test across the points. When the continuity is broken, the points have just opened, and this is the instant the spark is generated.

With the spark plug removed, a simple mechanical depth gauge can be used with a Vernier caliper to find the piston position. As an alternative, a depth micrometer can be used to make the same check.

The tool used to check the piston position is shown on the left. A spark plug body with an extended brass top. The moving part was a loose fitting rod with a locking collar. An alternative could be a Meccano rod with a zip tie.
As the Puch timing was 0.8-> 1.2mm a 1mm thick washer was added to the depth tool where shown.

The spark plug should be replaced with the depth tool body.

The points gap must be set first by rotating the engine until they are fully opened and then setting the gap to be 0.4mm via the pinch bolt shown above.

For checking when the points open, the point wire shown should be disconnected from the condenser. This is most easily done by removing the flywheel but then the flywheel needs to be replaced.

Then the depth rod can be inserted along with the 1mm spacer washer.

By rotating the engine and "rocking" it about the TDC it should be possible to find the position where the depth rod sticks out the most. This is TDC for the engine.

With the depth rod touching the piston top, the sliding collar should be pushed down to touch the spacer washer and the grip screw tightened.

Without changing the collar position the washer can then be removed to leave a 1mm gap under then collar.

Then the engine can be rotated backwards until the collar touched the tool body again. The piston is now 1mm before TDC.

A multimeter should be connected between the points wire and earth, and the ignition turned one. The three stator plate screws should be slackened.

Using a screwdriver as shown it should be possible to rotate the stator plate to find the position where the continuity is just broken. This is when the spark will fire. (Flywheel not shown for clarity but will need to be fitted for this to work).