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Little ole lady owned RX7 12a rebuild

Old 01-07-19, 04:57 PM
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Little ole lady owned RX7 12a rebuild

Long time lurker - first time poster.

I bought a 1982 about 6 years ago from a little old lady who was the original owner. The interior and body are in excellent shape. It had a vacuum problem they couldn't figure out so I took it on. After turning the Nikki into a Sterling Nikki, I believe now it to be a vacuum leak at the lower butterfly valve at the intake. I got tied up with other things and the car sat (and sat and sat). I'll deal with vacuum later. First I want to get the engine back to working order.

So the engine was factory rebuilt 15 years ago by Mazda (I understand they used to rebuild their own engines but no longer do that.) The rebuilt engine only has 3k miles on it. I have the engine out of the car and on my workbench. I'm ready to tear into it, but before I do, I thought I would see if anyone has any advice. I've considered everything from rebuilding it myself to trying to sending it off to source a 13b to replace it. I want to make the car a long commuter car if possible. Any advice would be appreciated.

Thank you in advance.
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Old 01-07-19, 06:56 PM
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I'd recommend installing a proven stock Nikki carb back in there on the bet that the 12A is fine and the problems are with the modded carb or associated vacuum plumbing.

One time I tore down a 12A that I should have just used as it was, there were no problems inside. Not one of my better moves.

Incidentally, I'm currently commuting my 83 Limited Edition into Atlanta and back each day, 110 mile round trip.

Great highway cars, those FB's!
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Old 01-07-19, 08:40 PM
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Well, when I started, the carb was original. There is a problem there. It would run but you had to hold the choke on. If you let the semi auto choke drop, it would die. I didn't do anything to the carb I can't undo, so I can reverse the rat's nest. I made block plates, etc. But that is why the carb was modified: I knew it was a vacuum issue but no one could find it. Removing as much of the emissions seemed like a logical way to get it back on the road.

But if it IS the lower butterfly, there is no reversible fix that I know of. I either have to replace it or drill it out.

Went to undergrad at GT. Great city, Atlanta.
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Old 01-07-19, 08:50 PM
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With only 3k miles, are there engine rebuild parts I WON'T need? I'm all about "while I'm in there", but with those few miles on this engine, I hate to waste money.
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Old 01-07-19, 09:41 PM
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Couple things...been a long time since Mazda dealers? rebuilt any rotaries,1st hand info on this,"factory rebuilt" would imply it was sent to Japan to be rebuilt? Do you have paperwork that shows who did what to it? Who was the "they" that couldn't figure out the vacuum leak?
Vacuum leak you describe likely a defective shutter valve,very common problem,easily diagnosed & repaired. Why would you remove a rebuilt engine with only 3k on it,was it locked up,did you check compression while still in the car,what's your reason for disassembling engine?

Take Ray's advice and rethink opening up that engine unless you have a valid reason. +1 on stock Nikki that came on the car not being the problem,unless it had a plugged idle circuit. I would assume you've cleaned and rebuilt it?
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Old 01-07-19, 10:25 PM
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I apologize for my missing information. I have a receipt from the Mazda dealership for a rebuilt engine so I assumed Mazda rebuilt it. Maybe that was a mistake and it was just the local mazda dealership. But it also has a plate on it which reads "remanufactured product - model number C FA30 39 - Serial Number CD 00525 06/03" Looks pretty official. Can't imaging a normal shop installing a plate like this. But maybe. What's that about assumptions making something out of me (and umptions)

Now it is locked up. At one point, I tried the ATF trick and it didn't work so I assume (again) the ATF has settled into the bottom and gunked up the rotors. If there is a way to get it freed, I'm all ears. Also, when I last tried to crank it, it make an awful screeching noise. I think it might just be the starter (I have a new one on the shelf), but it made me very concerned I was tearing up the housings.

When I bought he car, the lady met me at her mechanic's shop. He couldn't figure it out. I tried spraying parts cleaner, etc to pinpoint the leak but I couldn't figure it out either. I've rebuilt the carb. Yes - the agree the shutter valve is probably the culprit.

I've rebuilt piston engines (spitfires and land cruisers). I'm not a complete noob, but this is my first rotary. I appreciate the help.
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Old 01-07-19, 10:29 PM
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Also - the compression was fine when I last checked it years ago. But that was before it sat for a while and I heard the screeching. My concern for the housings made me think I had to rebuild. And now that the rotors are stuck...

Last edited by bmorgan5; 01-07-19 at 10:43 PM. Reason: Original post wasn't complete
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Old 01-07-19, 11:12 PM
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I just re-read your post, GSLSE - again, it's been some time, but I recall checking the shutter valve. I don't think that test failed - although it does seem easy enough to replace and in turn rule that out. I was thinking more that was the lower butterfly valve in the intake manifold. I read somewhere it can leak along the shaft and the only way to fix it is to drill it out and JB weld it shut. I'm anti making changes that can't easily be reversed, so I didn't do it.

Does this sound right? Could this be the original problem?
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Old 01-07-19, 11:38 PM
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"Locked up"? like the engine doesn't spin at all? But you wrote that it makes screeching sounds; so it moves?

Stop it with the atf... Just for now

Using the flywheel try rocking the engine back and forth (there is no timing chain/belt to worry about reverse engine movement). If you hydrolocked it with atf then you should be able to get it to squirt the excess oil out through both sparkplug holes and intake holes.

If you can get it free to turn then you can check the apex seals by turning the engine over and looking at them through the exhaust ports. (there are six seals between the two rotors). Check each seal for "springiness" with your finger. You just want to poke them with your finger and make sure they can move in and out a little bit.



You said you did a compression test, but what where the numbers on each face? One solid number followed by two lower numbers is going to be an apex seal failure (whether spring or actual apex seal you won't know till you crack it open) Spring failure sometimes can be resolved by working the apex seals (MMO and ATF have detergents in them which loosen up carbon; hence the "atf trick"). I use the term "spring failure" loosely, but you could just have a build up of carbon from not redlining enough.


I'd second cracking the keg as a last resort.
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Old 01-08-19, 12:07 AM
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Without having the car in front of me,but hearing described symptoms,three possibilities come to mind.
Plugged idle circuit in carb,not as likely as defective shutter valve,or leaking diaphragm in brake booster. My money on shutter valve-but no definitive test can be done without a running engine.

When the engine was still in car,did you try turning it by hand or only with the starter.
ATF not the best choice for putting in engine to break up possible carbon lock.
Marvel mystery oil,Seafom would be 1st choices.
If you can't turn engine by hand,no point in trying to crank with starter.

Have to wonder how poorly the engine was running to have that much carbon buildup in 3k miles? Or was/is there a mechanical problem causing lock up/screeching,maybe broken apex seal or some foreign material got into engine...

How many miles on car,what happened to the original engine that it had to be replaced? Manual or auto trans?

Regardless,if the engine cannot be turned by hand then it has to be disassembled to find out why. Repair whatever is causing it to not turn. Put it back in car,get running and diagnose the no idle problem. A quick test is to take air cleaner lid off and plug opening in air cleaner base temporarily where shutter valve gets its fresh air. Follow hose from shutter valve to bottom of air cleaner to know which tube to block off. Normally you can hear the sucking sound at that opening in air cleaner when shutter valve is defective.
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Old 01-08-19, 12:10 AM
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I would wait til engine is apart and problem identified before ordering any parts,gaskets,seals.
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Old 01-08-19, 10:54 AM
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Originally Posted by bmorgan5 View Post
So the engine was factory rebuilt 15 years ago by Mazda (I understand they used to rebuild their own engines but no longer do that.) .
Due to Mazda's patent rights on the Wankel engine they were not allowed to sell new engines, so they had a reman facility to rebuild rotaries and automatic transmissions

Originally Posted by GSLSEforme View Post
Couple things...been a long time since Mazda dealers? rebuilt any rotaries,1st hand info on this,"factory rebuilt" would imply it was sent to Japan to be rebuilt?
Mazda USA had a reman program, they were all done in the USA. they currently only reman the Rx8 engines (i think), the FD engines are new, and everything else is not offered as an assembly in the US

Originally Posted by bmorgan5 View Post
I apologize for my missing information. I have a receipt from the Mazda dealership for a rebuilt engine so I assumed Mazda rebuilt it. Maybe that was a mistake and it was just the local mazda dealership. But it also has a plate on it which reads "remanufactured product - model number C FA30 39 - Serial Number CD 00525 06/03" Looks pretty official. Can't imaging a normal shop installing a plate like this. But maybe. .
if its a Blue tag it is a Mazda reman.
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Old 01-08-19, 11:16 AM
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Qingdao: The engine isn't turning freely anymore but it once did. And the last time it did, it made a screeching sound. And actually, it wasn't just ATF - I also put some Marvel in there too. It's been sitting for way too long. I know - it's my doing.

I'll see if I still have the compression numbers. It was at least 5 years ago, so I don't remember. I just remember thinking the numbers looked good.

GSLSE: I don't know why the original engine was rebuilt. The car has 136k miles on it - the rebuild done at 133k. It's a manual. The day I bought it, my wife was driving it holding the choke on while i followed. We got within one mile of the house and the slave cylinder went out. I've only driven the car once since then (just after I replaced the cylinder.) That was in 2013.

Do you think there is any way to get the ATF / Marvel out without a tear down?

J9FD3S: Yep - blue label.

Last edited by bmorgan5; 01-08-19 at 11:18 AM. Reason: typo
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Old 01-08-19, 02:19 PM
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What's in the engine fluid wise is not an issue. Again,if you cannot turn engine by hand either direction with plugs out it will have to be disassembled to assess why.
Try to turn one direction then the other,don't force it. If it won't move at all either way it needs to come apart. At this point you don't know if it's carbon locking it or something mechanical damaged inside. If you can get it to move one direction a bit and it stops,try to turn it the other.
You may be able to keep working it back and forth to get enough movement to possibly turn it a complete revolution. As you're doing so stop and look thru exhaust ports at apex seals,there are 3 per rotor,total of 6. Push each seal down slightly,it should spring back to its original position. If there's loose carbon in the engine it will be around the apex seal area if you were able to free it enough to turn. If the engine feels notchy or not smooth,again,don't force it.

If time is on your side,pour some sea foam in intake and exhaust ports and let it sit several days and try again. Look for any debris or gouges in rotor face as each face rotates past the exhaust port. I have,with patience,freed carbon locked engines before. Some ran fine afterwards,some had to be disassembled for diagnosis/repair
You could get lucky...
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Old 01-08-19, 03:05 PM
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Thank you. Seafoam poured. We'll see.
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Old 01-08-19, 06:25 PM
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i hope that you get lucky!! shame on you for letting the car sit...these are to much fun to drive how can anyone let them sit.(i understand life gets in the way)
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Old 01-08-19, 09:23 PM
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I know. I feel bad about it. I hope the RX7 gods will forgive me. I'll do my best to make it up with the soon to be resurrection.

Too many projects. A wife and 2 year old. blah blah blah - excuses excuses. I'll do my best. I really appreciate everyone's help here.

I'm always surprised how willing people are to help total strangers. It's a good feeling.
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Old 01-09-19, 12:22 PM
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There’s a lot of good information on here. Someone will help you get it squared away.
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Old 01-12-19, 10:36 AM
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Stuck like chuck

Any idea where to get a rebuild kit? The Mazda folks near me say their catalogs don't go earlier than '86. Anything helps.
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Old 01-12-19, 11:08 AM
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Originally Posted by dcast122 View Post
Any idea where to get a rebuild kit? The Mazda folks near me say their catalogs don't go earlier than '86. Anything helps.
the catalog doesn't go that far back so you need to look it up yourself, they can still get the parts. we tell Mazda this is dumb, they don't see why. dumb part B is that this new catalog is flash based so it goes away next year.

dumb part c, parts list is here, from Mazda

https://www.mazdamotorsports.com/partslists/
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Old 01-19-19, 07:19 PM
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Not sure which rebuild kit you're looking for but if it's for the Nikki they are still available, although they've gone up about $10:

https://www.autozone.com/fuel-delive...60809_585426_0

https://www.rockauto.com/en/catalog/...epair+kit,5964
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Old 01-20-19, 12:02 PM
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Just a quick update: I had to go out of town for a few weeks for work so the engine is sitting with seafoam in it. Turns out my brother-in-law has an engine rack I can borrow so that might help. Right now it's just sitting on a workbench. I'm thinking of trying to put a heat gun to the bottom - not too much - just to warm it up (no open flame). It will be next week before I am able to try this.
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Old 01-20-19, 03:53 PM
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I had a 12A that was seized up in my silver 85 GSL after sitting a few years, couldn't break it loose with a 3/4" ratchet on the eshaft..

The 12A was still in the car so a bit easier to work on than yours, but if you can fix it to an engine rack that will help.

I did the seafoam thing, waited several days and then put a breaker bar on it, starting by gently working the bar back and forth and increasing the torque a bit each time.

Eventually it broke loose, the car started up and I put another 50,000 miles on that 12A before selling the car with 150,000 original miles.

And the 12A was still running strong.
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Old 01-20-19, 07:16 PM
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Exactly what I need - HOPE!!!!

Thanks Ray.
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