Motoplat CDI - pickup gap?

[Jordan]

I think there's a specified air gap for the trigger sensor, rotor to stator, for the Motoplat.
There is some play available for setting this, as the stator is slightly smaller diameter than the housing.
I can't find the figure at the moment.
Can someone please tell me if they know what it is?

[Jon Pegler]

Neither the Motoplat handbook or the Mototrans handbook give a figure for an air gap for the Motoplat electronic ignition pick up on a Ducati single.
I would just fit it and strobe time afterwards.

Jon

[Jordan]

Thanks Jon.
I did read, somewhere, some spec for the Motoplat pickup gap on Ducati singles.
Variation of the gap has an effect on the trigger waveform shape, which could then vary the advance range.

[CaptonZap]

Since you are dealing with an electro-mechanical device, you have to make allowances for two different sets of variables. The coils produce a standing magnetic field, which the reluctor disturbs when it passes through. So the closer the reluctor to the pole of the electro magnet, the stronger the effect.
On the other hand, the reluctor, being metal, can expand and contract with temperature changes, and loose bearings and balance factors can induce bending of the components involved, no matter how minute, and manufacturing tolerances may not be conducive to the assembled units to all have the same clearances, so you have to allow some fudge factor. Ideally, you would want zero to one thousandth clearance, but due to the afore mentioned reasons, you can not rely on the clearance remaining at that point during a run cycle.
If your bearings are good, and the circumference of the rotor is concentric with the main shaft center on rotation, three or four thou would work. As a point of reference, Yamaha calls for 7 thousandths clearance on their ignition pick up coils. They will run with much greater than that, but as was mentioned, the timing may shift a bit. Can you detect one or two degrees difference in timing?

CZ

[Jordan]

G'day CZ,

There seems to be a lot of variation amongst the various gaps from different makers.
On mine, it can be between approx 0.25 and 1 mm. I set it at 0.35, about 14 thou which seems to work alright.

Strictly speaking, the Motoplat doesn't have a reluctor. Its rotor has a magnet in it.
Any centrifugal or thermal effects are probably too small to matter much.

Thanks for your thoughts.

Jordan