ultimatejay

iTrader: (1)

I just got done searching for .5 hrs and could not find any info to really help.

Can someone please post some pictures of a 12a front counterweights from pre 83 and one of 83-85 manual transmission. I just tore my 12a apart that I bought second hand and I have the lighter 83-85 rotors for sure and an 81-82 rear flywheel. I have no idea what front counterweight I have. I want to buy a new aluminum flywheel and want to get the right front counterweight for the 83-85 rotors. Here is a pic. of the front counterweight that I have. Thanks

Jarrett

waysrx7

This probably wont help but here is a pic I just happened to have on the computer. I'll try to take some more tomorrow. It's from on 85 I believe.

ultimatejay

iTrader: (1)

So it looks like mine and yours are the same. So I am thinking that the older, heavier 12a rotors would have a larger front counterweight? Mine looks to be 1/4 circle. What does the older front counterweights look like? Thanks

gsl-se addict

iTrader: (3)

Check here:

https://www.rx7club.com/1st-generation-specific-1979-1985-18/identify-these-rotors-708362/

David Dewhurst

iTrader: (2)

***I want to buy a new aluminum flywheel and want to get the right front counterweight for the 83-85 rotors.***

When a person changes to a lighter flywheel one changes the rear counter weight...... I don't know all the is & outs of a rotarty motor but I have never head of anyone changing the front counter weight. I was of the impression the front counter weight is to balance the e-shaft with zero respect to the rotors. ????

Jeff20B

iTrader: (13)

ultimatejay, you have an '81-'82 front counterweight. waysrx7 is '83-'85. Look closer.

ultimatejay

iTrader: (1)

I can't really make out any differences. It looks like mine might be smaller?

So if I want to use the 83-85 rotors then I need the front counterweight that is pictured by waysrx7?

trochoid

iTrader: (6)

Simple, install the auto tranny counterweight that matches your engine, along with the lightweight flywheel, done. Light flywheels have a neutral balance so all one needs to do is match up the front/rear cws with the rotors.

ultimatejay

iTrader: (1)

Thanks for the input, but here is my problem and why I started this thread. I bought a 12a bridgeport used and the rear apex seal blew. So I tore the motor
down. I have mixed matched parts all over the place. That is why I need to know what front counterweight I have because I have a flywheel out of an 81-82 and it appears that I have a front counterweight out of and 81-82- as mentioned by Jeff- but I have 83-85 rotors. See my delema? I want to make sure I have the correct front counterweight for my 83-85 rotors so that I can buy the right flywheel with correct rear counterweight for 83-85.

So tell me if I'm wrong here but it appears that all I need is a front counterweight for 83-85 and then order my flywheel and rear counterweight for 83-85? Thanks

waysrx7

The 83-85 counterweight looks more like a triangle with a straight radius yours has a curved radius.




sounds right to me.

trochoid

iTrader: (6)

If you have N rotors, yes.

ultimatejay

iTrader: (1)

Thanks, perfect. That's what I was looking for. I can really see the diff. in the pic you provided. Thanks for your help too Jeff, and trochoid.

Anybody know where I can get a front counterweight for an 83-85?

ultimatejay

iTrader: (1)

Yes I have the N rotors F and R with the "N'" on both of them and confirmed they both weighed 9.5 lbs- the lighter ones.

Jeff20B

iTrader: (13)

I'd offer you mine, but I'm down to my last two and still have two 12As to build. If I play my cards right, one will be a stock port or '74 spec port and go into a front wheel drive project (gasp FWD!) and the other will be a 6 port 12A using a set of RE-SI (super injection) side plates. As you can see I have big plans for my '83-'85 12A stuff. I also have big plans for my '71-'73 twin dizzy 12A - it's going into my baja. The KEP kit arrived today.

I still have two or three 4 port 13Bs to build, but they're becoming somewhat routine by now. The real action is the 12As.

RXDad

iTrader: (2)

Any chance we can archive this? This is an important but not often covered topic.

Thanks
RXDad

waysrx7

This thread will be complete when we get a picture of a pre '81 front counterweight, the one that looks like a half circle. I don't have one but if someone else can post a pic of one this would actually be a good thread.

David Dewhurst

iTrader: (2)

***Simple, install the auto tranny counterweight that matches your engine, along with the lightweight flywheel, done. Light flywheels have a neutral balance so all one needs to do is match up the front/rear cws with the rotors.***

I was aware of correct auto counter weight for the motor while I guess assuming the correct front weight is in place. Thanks, learned something new to be aware of.

ultimatejay, I have a counter weight & flex plate for 83/85 motor. Please pm if interested. I'm changing to race Spec Miata. I also have some other RX-7 stuff including a 82 RUST FREE that's stripped & ready for a cage. Five transmissions, a couple drive shafts, two motors, the early good intake, Blaster coils, Auto Meter gauges & more.

RXDad

iTrader: (2)

'78 to '82 Front Counterweight:



RXDad

Howco

I know this has nothing to do with nothing. But is your name Jay Jarrett?

Jeezus

iTrader: (4)

Since we are on the topic of counterweights, I just so happened to look through my stash of parts, and found this. Is this the rear?

waysrx7

^^ That sure looks like the pre '81 front counterweight, thanks for the pic.

Jeff20B

iTrader: (13)

That looks like GSL-SE because it has a 45° angle on the outer edge. But yes, it is a half circle like the early 12A. All 13Bs have a half circle.

ultimatejay

iTrader: (1)

Cool, anyone else have any front counterweight pics. We should archive this and identify all the front counterweights for various rears.

rx7learner

85 counterweight and N rotors with MT (in process of a rebuild... still scrubing my rotors....)

ultimatejay

iTrader: (1)

Just Jarrett.