Wipac mag

[vhgmcbuddy]

Has anyone, or can anyone direct me to any manuals on a Wipac magneto fitted on the Gem 810cc twin. my neighbor has taken his apart to clean and dry it but has taken out the distributor cog.
I just need some guidance on how to re-fit. The drive cog has a witness arrow but the rotor cog has no marks.
Any ideas.

Phil

[trusty220]

The magneto type should be A955BZ if anyone has a service sheet for this model- unfortunately I’ve got everything but that one!

[charlie]

The A955BZ is for the Gem but is for single cylinder engine!
The Gem series IV with the 360 twin engine had an A1483HZ magneto other Series IV Gem had an A1137BZ. I have service instructions for both.
Do you mean the magneto drive gear or where the rotor arm is fitted?
There should be a plate on the magneto saying which type it is.

[vhgmcbuddy]

Yea Charlie, it is the A1483HZ but my problem starts with him taking the rotor arm out without making a note of where it should syncronise to. There is no mark on the rotor although there is a witness arrow on the small drive shaft, opposite the keyway. The rotor has been damaged in the past but it did work until he decided to leave it out in the rain, this is when he took it apart to dry it out, no problem “I’ll give it to Phil, he’ll fix it”?
Attached are photos of what I have. I presume then I can stick my finger in the plug hole, feel for the piston and time the points just before TDC.
Or at least that’s what I was thinking, not worked with this type of mag before.

Cheeers!
Phil

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[charlie]

Copy of service instructions attached. The rotor arm looks different to the one you have.

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[vhgmcbuddy]

The part in the diagram looks like a proper rotor arm and will just fit straight on to the main drive, where on this mag it is a round cog type rotor and this is where I can’t figure out how to fix the rotor back so the timing is true.

if I could find any witness arrows or mark to line up with the main drive, I don’t know if I am explaining this too clearly

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[charlie]

Interesting, that is different from what the service instructions show. I will have a look through what info I have and see if I can find that type of rotor arm. It looks as if te gears drive the rotor arm at half speed ie a 2:1 reduction, counting the number of teeth on each gear will confirm this.

[vhgmcbuddy]

Your right Charlie the drive is 13 teeth and the rotor is 26 teeth. 2:1 reduction.

[charlie]

I have had a look through all the Wipac information I have and cannot see a rotor arm like that anywhere. I did find a service bulletin showing a new type gear housing, see attached. All the multi-cylinder magnetos appear to have a conventional looking rotor arm.
Looking at the photos and thinking about how it works, if I understand the operation correctly. The external contact on the rotor needs to be in contact with one of the plug lead contacts on the distributor housing at the point where it will fire ie when points start to open. It should be possible to set magneto at a point where points start to open; then without moving magneto rotor shaft,attach distributor gear housing and set rotor arm to one of the plug lead terminals.
It may turnout that the witness mark lines up with the metal strip on rotor arm at this point.

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