ultimatejay

iTrader: (1)

On a 12a is the front and rear rotor different or are they interchangeable. And if they are diff. how do you tell them appart?

Thanks, I have searched but could not find anything.

waysrx7

If you look at the pic you see the combustion bowl, if you switch a front rotor with a rear rotor, the bowl will be upsidedown.
Not interchangeable.




To tell if it's a front or rear rotor you have to know which side the gear is on.
I can't remember off the top of my head by I can let you know tomorrow unless someone else already has.

Jeff20B

iTrader: (13)

You have an '83 to '85 rotor sitting there.

waysrx7

Sure do. It's an '85. I don't think I've seen pre '83, what do they look like?

twistystraw

sorry for the noob question but how can you tell?

blwfly

iTrader: (4)

iirc
combustion bowel is a little narrower
and the "f" "r" lettering is diff.

Jeff20B

iTrader: (13)

It has an N and a large cast R. The N means '83-'85.

waysrx7

This is a rear rotor. The gear is on the right side so when it is rotating in the engine the bottom or larger part of the bowl reaches the combustion chamber first.
A front rotor will have the gear on the opposite side.

ultimatejay

iTrader: (1)

Thanks guys for the help. I am tearing down my first rotary tomorrow. So the larger bowl is always facing down towards the oil pan.

twistystraw

Woah sweet i never knew they put imprints into the bowls. Is it typical to have that much build up on the rotor?

dj55b

iTrader: (2)

acumulated over 22+ years yes ... take the rotor face onto a wire brush attachement on a grinder and should take care of it all. Make sure the wire bruch is brass to not hurt the surface.

ultimatejay

iTrader: (1)

Just got done Dissasembling my 12a. Took about an hour. The front hub bolt was a little tight and the rear stat gear was a biotch to get out. Took one hour and that was fighting sticking components like the dowl pins- I need to make a tool for that.

Quick question. I only have one apex seal spring for each apex seal. Is this normal on 12a's? On the 13b's I know they have two springs- one small and one larger one for each apex.

Jeff20B

iTrader: (13)

3mm seals use one spring.

ultimatejay

iTrader: (1)

Thank you. I figured as much because there is only 1 ridge on each side of the seal but I wanted to make sure.