ok i just bought a 80 rx7 yesterday night guy said its bin sitting for a year after he put the following street port 3mm apex seals 2 new housings racing beat intake mani with holly 750 racing fuel pump with manuel regulater new aftermarket radiator ok my problem was the guy says that to start the car u need to put oil in the carb or it wont start so i go to buy it he puts oil and starts rite up smokes like a bitch tho but runs at 2,000 rshared_pm then would slowly idle lower till it died so my cuzin did some work on the carb and made it idle at 1500 and idle steady not die any lower and it will die u turn the car over and it wants to start but wont untill dat oil hits it ran a compression test 100 psi in the first rotor 60 in the second closest to the tranny my guess is the rotor is fucked with is wat my uncle says and he states he built rotorys b4 and he said the rotor was fucked up b4 the compression test if any good mazda people have gone thru or kno please let me kno ur opinion

 

i would say start with a rebuild but iono im not pretty new to rotarys as well but on a compression test that sounds pretty sucky to me

 

yea but the last thing i wana do is open it up and ive heard rotors are expesive and the guy said the shop that built it said the old rotors have to seat with the new housings then it would b ok

 

Sounds to me like home boy got you. The front has 100 and the rear rotor is only pulling 60? How long does it need to seat in? Its not a piston engine..... Cides why would the engine need new housing? Simple answer.... cuz he f%^&*d up the apex seals wich scared the hell outta the housing.... which explains the 3mm seals... or he butchered the port.... in which case, he' have to start over...

Anywho, it sounds like the rotor itself is toast in the rear.... which could run you a pretty penny pending what you wanna put in it. The next trick is getting a rear rotor that will balance with the front rotor. they have weight codes stamped on em, and mazda or some of the rotary shops will be able to tell you which codes match up. You may need to get the new rotor, or slightly used rotor machined to balance out. Get on RX7club.com and throw up your issue in the 1st gen section and then go to the for sale section and try and hunt down 12a rotors... Still may be the housing thats messed up... but with a 3mm seal, i would say its the rotor. Could be something as simple as dude not putting the seals in properly, or could be a f%^&d up rotor... either way, you gotta open the keg to find out.


food for thought, while your contemplating what to do, find a matching set of 13b rotors that are still in spec, and put them in the 12a. Look around on 7club and google and you'll understand what im talking bout. I think you'll like the benefits of that better than rebuilding what you have now.

 

just put this instead and yell be much happy with the results haha

 

ALL ROTARY ENGINES BEFORE 1986 ARE 3mm apex seals. I think it's got used seals or something.. rotor could be fine. I'd open it up, MEASUER EVERYTHING, and replace all the worn parts that need to be replaced. BTW, I want to say about 75 psi is the minimal # for compression. 60 is definitely low compression, but you may have more useable parts than if a seal was blown & you were reading 0 - 0 - 0. BTW- was it 60 & 100 on ALL ROTOR FACES?

have fun.

 

^ interesting.. i didnt know 3mm was standard on the FB's. Thats good to know. Im assuming the rotor is damaged since he needed new housings.... but i could be wrong. But the common theme here is that you gotta open it up to see whats going on.... And people re use apex seals alot. I have even heard of guys re using bent apex seals after they hammer em back out... So, get in there and see whats going on. Also, there are 3 seals per rotor, as landon was getting at, you should check compression on all three sides of each of the 2 rotors. That will give you a better indication of the seal being bad.

 

Sounds like a rebuild with used seals! These engines are very touchy when disassemble and assembling If the rebuild has brand "NEW" housings the car will never show 60 psi unless the apex seal were reused.The only time you can reuse Apex seals is if they come from the original housing. So say you have a 12a never open, when you take that engine apart the three apex seals go with the original housings it comes from. Rotors are not supposesd to be interchanged from front to back cause then balance of the engine will be gone! Rotors rarely go bad usually when you break apex seals or Rotor bearings go out thats when Rotors can get damaged.....

 

If the engine is smoking really bad without putting oil to start on then car the your oil control rings are bad (oil seal on the rotors)! Most likely were also reused

 

^ Sammy i believe the car wont start without the oil being added? But maybe i misread that?