12a Rebuild Experience
 

Ok, I asked the question a few weeks ago if rebuilding a 12a is a serious project. I had several members respond that if I had some experience rebuilding engines it should not be too much of a problem. Well, I have some limited experience, but I’m not a mechanic. For those of you that are asking the same question below is my answer.

I have an 85 RX7 that has a street ported 12a and a standard carburetor, but the engine developed a serious stream leak after only 16,000 miles. I determined that the leak was located between the front housing and the front rotor housing. Rebuilding or disassembling the engine was the only option to correct the problem.

1st, if you have no experience rebuilding engines buy the Atkins video or something similar to guide you through the rebuilding process. In my opinion, attempting to rebuild a 12a or 13b without a video will cost you in the end. 2nd, setup a TV with VCR and follow the video step by step to ensure that you do not make any mistakes. Even though the Atkins video is excellent I would recommend watching the video a couple time before attempting to rebuild your engine. 3rd, make sure that you have all of the required tools to complete the job. Don’t waste your time thinking you can get by without the 2 1/8” socket or any other required tools. Buy what you need to get the job done. 4th, after you disassemble the engine complete a thorough inspection and cleaning of all parts. If you find damaged parts (housings or rotors) replace as needed. In my situation all major components were in great condition, so replacing side seals and gaskets was all that was needed. Check out you apex seals and springs and if you have any wear, replace. As a precautionary measure label the rotors and housings to eliminate confusion. You really have to look hard to find the small F & R on the rotors to determine the front from the rear. Last, after you assemble and install the engine the biggest hassle is starting up the engine. Before you attempt to start the engine pour approximately 8 ounce of oil down the primary and turn the engine rotors manually with your NEW spark plugs removed. Some members recommended adding oil to both bottom rotors. Either way, make sure you add oil to the rotors. After addign the oil I rotated the engine rotors 20 times manually and waited overnight. Attempting to start your rebuilt engine with the starter could burn out your starter. After you rebuild your engine you will find that it is very hard to turn over. Take some time to work with the engine to free up the stiff seals and lubricate all internal components. If you can spin the engine with limited force you should be ready to go. Lubricating the rotors is very important, because you don’t want to attempt to start the engine with dry rotors. Oh yes, verify the all belts have the correct tension, install your NEW plugs, verify correct oil level and anti-freeze, because once your engine fires up and is running allow it run without interruption at least
1½ hour’s. At startup you will hear various noises that you may question, but let it run. If you followed the instructions in the video the engine will have not problems to address.

Overall I would recommend rebuilding your own engine. I paid someone the first time and it cost me twice. If you have time and interest in learning more about rotary engines don’t pay someone else to rebuild your engine. The 12a engine is very simple to rebuild and you will invest approximately 3 hours in time to complete the rebuild. One person can do removing, rebuilding and reinstalling of a 12a engine with no assistance from anyone (other than the Atkins video) throughout the whole process. No question, if I can rebuild a engine anybody can. I know that I missed explaining a lot of steps in the process, but I attempted to hit what I considered to be the trouble areas. I searched and found several messages that provided some of the required information, so hopefully this message will help someone down the road.

Thanks. I've been kicking around the idea of getting a junkyard 12a and doing a rebuild. This helps. I forgot to add tools into my budget.

I know this is an old thread, but a 12A is still a 12A.
Thank yo.

This makes me want to try a rebuild on my own with my brother on his FD lol

Wow I didn't know this threat was that old..

2nd, setup a TV with VCR

Hahaha does anyone have the Atkins video on Betamax? Old but the advice is still solid.

Having bought all THREE DVD Rebuild video tutorial sets (they all say 13B, but no real diff) - I can say, with all due respect to Atkins, the mazdatrix one is the best value; certainly more up-to-date and better produced than the Atkins version. 3rd set (of 3 DVDs!) is the New Zealand one, which is really excellent if you are OK springing the $110-ish for it vs $30 for the Mazdatrix. $110 is small change for your time and the cost of the rebuild bits.....

AND-
some fabulous, FREE prep and build video tips on the Pineappleracing.com site with Rob Golden



Stu Aull
80GS
Alaska

How did you retorque the flywheel nut back to 350lbs? That's what has been holding me up on trying to rebuild one of my own. I don't have an impact or air commpressor. Nor can I find a torque wrench that goes that high

If you don't have an impact gun and a high volume compressor, you can use a three + foot beaker bar. Each foot equal 100 pounds. Make sure to secure the flywheel with a stop. And don't make the mistake I made by only using one bolt on the rear iron to secure the flywheel stop. I broke the rear iron doing this. Some people use a long bar bolted to the flywheel with the other end hitting the ground. Checkout Mazdatrix, I think they have pictures of several different flywheel stops.

The Mazdatrix DVD is excellent. Very good advice, well organized, and very detailed.

For the 350 ft lb rear nut, use a flywheel stop from Mazdatrix, the correct size socket and a breaker bar. Slide a steel pipe over the breaker bar and hang 100lbs of weight exactly 35" from the center of the nut. Having my 100lb girlfriend hang on there worked perfectly, and she got a kick outta it. Clean the threads with Acetone, use a dab of blue locktite and a new locking washer.

So I first got the Atkins video. Viewed it, well maybe I can rebuild the 12a, but I have many more questions. Got into a conversation at the auto parts store. Me "Thinking of rebuilding 12a in 84 Rx7" Clerk "1st gens: kings of drifting" Me (Drifting?) Googled drifting and up pops Drifting.com. Ordered the video. Then I read everyone is recommending the Mazadatrix video. What, now I need to buy another video? It arrived today in the mail, and it is the Mazadatrix video. This may be possible after all.

I know this is old but I figure I should mention this before anyone reads this and gets the torque wrong. It needs to be 3.5 feet not 35 inches. 35 inches is only 2.92 ft. 100lb*2.92ft=292lbft so if you did that you might want to look into fixing that, although if its not been a problem 350 may be unnecessary. Also it should be noted that this method only works if your lever arm (in this case your wrench and breaker bar) is exactly parallel to the ground. Otherwise you're only gonna get a fraction of the force being used to turn the nut.

The Harbor Freight electric impact is cheap and works well for tightening the flywheel nut.

True about the lever arm being as parallel to the ground as possible. I had to reposition the flywheel and socket a few times during the process of hanging concrete blocks (102 lbs.) on the end mark at 3' 5 1/4".

And this is why I love this forum. Great advice.

Meh. Just put it at the highest reading of your torque wrench (probably 150 ft lbs) and give the bolt a few more good tugs.

Well I'm not certain how important it is to be accurate so that may work... Then again that kinda thinking causes train crashes so I'll avoid it.

I didn't see those pictures before. That sir, is a beautiful set-up.

Here's some better advice; don't use an impact gun in any part of engine assembly. It's wrong technique, and you risk damaging parts.

Do it right.

I did use the reverse setup for removing the nut, the second time.
Please note the steel angle coming out of the base of the engine stand, with its end on bricks and a block of wood. Without this to stabilize the engine stand, the whole thing would have flipped over.

Something about necessity and mothers of invention.

Yeah that was a typo, 3.5 foot long bar and 100lb girlfriend hanging from it. But.... I bet it would worked the other way around 35" cause u know how girls lie about their weight :lol:

Or a one foot bar and a 350 pound girl friend.

Classic!