Gain access to the ignition system by prising off the aluminium casing from the side of the engine. This will reveal a heavy brass flywheel with access holes for checking points.
The contact breaker points are housed beneath the brass cap (see image) whose retaining arm must be swung sideways to open the cap. With a little careful manoeuvring, the cap can be removed through the access holes in the flywheel and the points gap can be checked and adjusted. The gap should be checked (probably 0.015”) and adjusted using the threaded adjuster and locknut as required.