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

 

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.

 

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

 

Check here:

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

 

***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. ????

 

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

 

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?

 

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.

 

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

 

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




sounds right to me.

 

If you have N rotors, yes.

 

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?

 

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.

 

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.

 

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

Thanks
RXDad

 

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.

 

***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.

 

'78 to '82 Front Counterweight:



RXDad

 

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

 

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?

 

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

 

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.

 

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

 

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

 

Just Jarrett.