Author Topic: Lucas Mo1 bearing insulator cups  (Read 272 times)

Offline mikeb

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Lucas Mo1 bearing insulator cups
« on: 28.10. 2017 06:58 »
can someone clarify if there are supposed to be 'paper' insulator cups under each bearing on a Mo1L?
currently, the bearing at the drive end shows a short with the housing - ok or not?

also I'm trying to get the one at the points end to fit but have ripped it. what's the best way to fit these things - i tried cup and bearing inserted together into housing and drifted in... hence the rip... arrg

is any ripped 'flower petals' bad or can i live with a few?

advice please! thanks
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Online beezermacc

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Re: Lucas Mo1 bearing insulator cups
« Reply #1 on: 28.10. 2017 08:05 »
All magnetos have an earth brush which allows the HT current to complete the circuit back to the armature. This is why, on a K2F, you often get an indentation on the earth track of the armature where the earth brush electrical contact has eroded the armature. The bearing insulation cups are there to prevent the HT circuit earthing back to the armature via the bearing, particularly when the earth brush gets oily or greasy. Theoretically, if the earth brush/armature surface is good, and the bearings are greased you could argue that the insulation cups weren't necessary but, as electrickery always finds its easiest route home, the HT current is bound to track through the bearings at some stage. Tracking through the bearing will wreck the bearings quite quickly so electrical continuity between the outer bearing and the body is highly undesirable.
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Offline mikeb

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Re: Lucas Mo1 bearing insulator cups
« Reply #2 on: 28.10. 2017 08:22 »
ok, so that confirms - yes - paper insulators are used at both ends/bearings and there should be no circuit between each outer race and the magneto housing...?

any tips on how to drive the outer race into the housing without wrecking the paper cups?

ta

EDIT: ok there's this: http://brightsparkmagnetos.com/condensectomy/drive_end_bearing_oil_seal.htm
probably worth a try. the lucas service sheet just says press them home which ripped the insulators
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Online chaterlea25

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Re: Lucas Mo1 bearing insulator cups
« Reply #3 on: 31.10. 2017 20:26 »
Hi Mikeb
The paper washers are available in different thicknesses
Trying to fit a thicker one than needed will cut them ,
That said they can be a pain at times *problem*
Relieve sharp edges on the housing, 
The most recent ones I bought are shiny on one side,
I found it best to fit the shiny side to the housing, a smear of grease will help
I made a "pusher" from a piece of "wooden" curtain pole machining a step on one end that's a
tight fit in the bearing race, this makes it easier to centre the race in the bottom of the housing

John
1961 Super Rocket
1963 RGS (ongoing)

Offline mikeb

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Re: Lucas Mo1 bearing insulator cups
« Reply #4 on: 31.10. 2017 22:33 »
John - good idea to make a centering 'pusher' - I'll try that.  i think your point about sharp edges is relevant. After ripping one I noticed that the drive-end housing had been peened a little around the bearing outer, presumably to hold the bearing in. so it had sharp edges. I've carefully filed those sharp points away and have ordered a few more insulators from brightspark (both sizes) and await another go.

I also noticed the points-end bearing had been 'shimmed' in the housing with a flattened piece of multi-strand electrical wire and had tape insulation only on the 'round' sides of the bearing outer. hence intentionally earthing the bearing outer. why i don't know. interesting what's been done to these poor old bikes over the years. hopeful it will run better once I've had my turn at it.
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Offline kiwipom

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Re: Lucas Mo1 bearing insulator cups
« Reply #5 on: 01.11. 2017 04:14 »
hi guys, Mikeb when i did my mag i drew up and printed my insulators from a different type of material, i made the tangs a little longer so they could be bent over the edge of the bearing hence not doing damage, cheers
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Offline mikeb

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Re: Lucas Mo1 bearing insulator cups
« Reply #6 on: 01.11. 2017 05:58 »
Thanks Kiwi.
what a good idea making them long enough to fold over the top (and trim later I presume). what material did you use?
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Offline kiwipom

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Re: Lucas Mo1 bearing insulator cups
« Reply #7 on: 01.11. 2017 08:13 »
Hi mike, it was a thin white plastic type electrical product, cheers
A10.G.Flash(cafe racer)Honda 250 vtr. Yamaha Virago XV920.

War! what is it good for?Absolutely nothing, Edwin Star.
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