One of the most difficult parts of stripping down a rotary or doing an engine swap for most DIY’ers is flywheel removal. Unlike most engines, the rotary uses a single large nut to hold the flywheel on. This nut is 2-1/8”, or 54mm.
There are various special tools made to remove the nut available from rotary shops, but the easiest thing is a 300ft-lb (or greater) impact gun. As for the socket itself, the most commonly available outlet is your local Sears, which usually has them in stock for about $25. They come in ¾” drive, so you probably need a ¾” to ½” drive adaptor as well since most impacts are ½” drive.
IF you don’t have access to air tools and don’t want to take the engine to the local semi garage to get it removed, you can use a long breaker bar and do it manually. You’ll need to secure the flywheel from turning. There are mazda tools called flywheel brakes available for this, which bolt to the bellhousing bolt holes on the block, and mesh with the ring gear. Since most of you won’t have access to those tools, the quickest way is to get a 4 or 5 foot piece of metal tube/bar, drill 2 holes corresponding to 2 flywheel/pressureplate mounting holes, and bolt the bar to the flywheel adjacent to the floor so that it cannot spin when pressure is applied…you might still want to stand on the end of the bar to secure the engine while torque is applied.
Once the nut is removed, you’re only halfway there. Leave the nut threaded on the end of the shaft. Note that the shaft is tapered, it gets larger as it goes inward. This means that the flywheel’s material actually expanded around the shaft when the nut was previously tightened, meaning there is a lot of energy stored up there that must be relieved before the flywheel will separate from the shaft. I’ve seen many people use heat (torches) and big pullers trying to get them off, only to break the puller or have no luck with the heat. My first time it took me over 4 hours to get it off…in reality it’s a 5 second job once the nut is removed.
You need a solid 4-5lb sledge to do this. ON the nonturbo flywheels, there are raised pads, some of which contain dowel alignment pins, some contain pressureplate bolt holes, and some are blank. ON turbo flywheels, the whole thing is flat, but you still have dowels, bolt holes, and blank spots in between. The objective is to hit these blank spots with your sledge…the leverage and force of the blow will travel inwards and shock the flywheel off the shaft. This will not damage anything externally or internally if done properly. Lay the sledge against the blank spot you’re aiming for, being sure not to hit the friction surface of the flywheel or the ring gear. Swing back about 1-2 feet and hit it hard one time in that spot. Grab the flywheel to see if it was loosened, if so remove it, and the key behind it. If not, take aim for another blank spot on the other side and swing again, a bit harder. Usually 1-2 swings gets it loose.
To reinstall the flywheel, you don’t have to do anything special, other than torque the nut to 300+ft-lb. For most impact guns, this means holding it wide open for about 1-2 seconds.