John Pritchett said:

Hi all, I have a 1969 500L. I have found that the distributor on it is from a 500R or 126 with offset keyway on the cap. It had a 500 round rotor arm which it shouldn't have, so I replaced it with the correct type 126 rotor arm. Now the centre electrode in the dizzy cap has almost worn away. I'm totally confused as the 500 type rotor shouldn't work in a 650 cap looking at it, but the correct rotor is wearing out the cap in a short time. Any ideas?

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Toshi 975 said:

From memory the distributor caps are not interchangeable as the locating key you refer to is in a different place. Is it a 499cc engine? Could be that someone has built a hybrid distributor from parts. If you can measure the height from the top of the body to the top of the rotor arm I can check it against a 126 distributor. If you are located near any other forum members then there may be a possibility of comparing distributors.

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John Pritchett said:

I'm totally confused as the 500 type rotor shouldn't work in a 650 cap looking at it, but the correct rotor is wearing out the cap in a short time. Any ideas?

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fiat500 said:

I just tested a 500 rotor in a 126 distributor and the engine worked as usual. A 126 cap fits a 500 distributor but the reverse is not true. The 126 cap has a more slender carbon-brush which seems to protrude less than the 500.........doesn't answer your problem but here's the images....126 on the left (except last image):

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John Pritchett said:

Should my distributor have a spacer between it and the block do you know?View attachment 202072

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Vitesse said:

Yes is the answer. I ran one in my 500 for years without a spacer for years with no problem but it was only when I upgraded to a 123 that I realised the difference.

Have a look at this thread it was discussed in here before. https://www.fiatforum.com/500-classic/461949-need-help-123-ignition.html?p=4362722

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John Pritchett said:

Thanks for that, I wonder if the lack of spacer is having an effect on the dizzy shaft and wearing out my cap?

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Vitesse said:

I assume you saw the picture of my dizzy on the other thread and you can see the wear on the gear at the bottom of the shaft only on one half. I would imagine that this one allow a certain degree of ‘slap’ on the shaft as it wouldn’t be fully meshed, so I suppose it could account for the wear?!

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John Pritchett said:

Yes saw the pics thanks, took the dizzy out today, no wear on the gear. There is about 3mm movement if you pull the shaft. Is that excessive? My cap is now in a bad state so put the original on and 500 rotor arm.

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John Pritchett said:

Yes saw the pics thanks, took the dizzy out today, no wear on the gear. There is about 3mm movement if you pull the shaft. Is that excessive? My cap is now in a bad state so put the original on and 500 rotor arm.

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Vitesse said:

I checked my distributor if I pull it from the gear end there is zero movement up and down. If I do it from the rotor arm end there is about 1-2mm movement.
It has the round rotor arm fitted and there is no excessive wear on the cap.

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