View Full Version : unlocking a 13 b 6 port

03-04-2002, 09:22 PM
who out there has expierience in unlocking a used rotary after sitting for some time.

motor is stock, has over 100k, was always in a heated garage and ports were completly plugged.

motor made one revolution before stopping and now will not turn. even with a breaker bar and pipe it refuses to turn.
i've contacted a few people but still open to any ideas.

thanks in advance

03-04-2002, 09:35 PM
mazdagt3, I can't remember the exact details of what I read or where I read it but I'll throw out the general tid bit I remember.

Carbon chunks lossen up drop free & jam against something (intake & or exhaust ports). Seems as tho it was stated that some sort of carb cleaner or some other marine liquid stuff was poured through the plug holes & into the combustion chambers & allowed to soak to break up or disolve the carbon chunk.

If I remember wherI read about this I will post the info.

Have Fun

David Dewhurst
CenDiv Milwaukee Region Spec-7 #14

03-04-2002, 11:19 PM
I don't know where I got this idea, but I seem to recall someone many years ago suggesting that Automatic Transmission fluid MIGHT free one up. I had one that was frozen and never could free up. I guess if I tried the AT fluid thing, it didn't work for me.

This sound familiar to anyone else?

03-04-2002, 11:57 PM
Yeah, ATF is a commonly used trick to temporarily restore compression after flooding, but no idea if it'll dissolve carbon.



03-05-2002, 02:22 AM
I had the same problem with a 84 12-A that sat for 6-7 years,the fix is easy.Get about 5 gallons of diesel fuel and pour it down the intake till it's full to the bottom of the carb or the intake plenum,let it sit for 2-3 weeks then gently try to turn it over. If it's in the car try 5th gear and rock the car.If it is still stuck repeat.Once it frees up pull the plugs and spin the diesel out and change the oil.Install fresh plugs and start it up treat it like a fresh motor for the first 500 miles

03-05-2002, 05:02 PM
mazdagt3, the attached post is copied from the Mr Mazda (Felix Miata)site. The address is http://mrmazda.members.alantic.net/main.html

I can never get directly in through the address so I go through the Milwaukee Region site & link my way through using the CenDiv Spec-7 link. I am not saying your motor is carbon locked, but if it is this seems like good info.


:Why is my rotary engine locked up? It started just fine when I moved it out of the garage to wash it. Ever since I finished washing it, all the starter will do is click.

This isn't good for any engine, but you found the rotary engine achilles heel. You are playing Russian Roulette by starting a cold rotary Mazda engine and not allowing it to warm up completely before turning it off. If you do this often enough, eventually one of two things will happen. Far more common is that you will flood it. The relatively rare, but far more disastrous, possibility is carbon lock. Just don't do it. If you must start it cold without letting it warm up completely, let it run at least two minutes. The longer the better.
Carbon lock is just what the name implies. A piece of combustion chamber deposit, which is made primarily of carbon, has dislodged from the face of the rotor and wedged in between the rotor apex and the rotor housing, preventing forward rotation.

If the engine has carbon locked, the only direction to turn the engine is in reverse. In-car this should be done only one of two ways. If your bellhousing has a hole aligned with the ring gear teeth, you can pry the flywheel through the hole. Otherwise you must remove the starter to use the flywheel ring gear teeth to force the engine to turn in the reverse direction of normal. Mazda makes a special tool for this purpose, part number 49 FA42 065 for manual transmission engines. Any other in-car method will just compound the problem, further wedging the carbon between the apex and the housing.

Trying to turn the stuck engine with the eccentric shaft bolt will only do one of two things: badly overtighten the bolt, preventing its later removal when the engine needs to be disassembled; or, loosen it, again accomplishing nothing regarding the s tuck engine. Trying to turn the stuck engine by pushing or pulling the car rarely works either. You don't have any control if you have to force it that way. Once the engine is broken loose, you don't want to turn it very far without determining if it will again stick going that direction. Once there is some freedom, usually the engine has to be worked back & forth until the carbon breaks into small enough pieces to let the engine turn all the way around freely. Towing or pushing the car in either direction doesn't allow you the use of any finesse.:

Have Fun

David Dewhurst
CenDiv Milwaukee Region Spec-7 #14