Lynn:

Is something missing; or do I not understand; see note below:

 

Remove all of the spark plugs.

 

Turn the engine in the direction of normal rotation until you can see an apex seal in the center of the trailing plug hole of the number one rotor housing. The rotor housing furthest from the prop. The upper plug is the trailing plug.

Removing the plug will reveal the hole.

 

Mark a flywheel starter tooth under your temporary pointer. Use welding wire or a coat hanger for a pointer, so you can bend it as needed. It needs to be well mounted and snug.

 

Once you have marked the tooth under the pointer with a paint drop, or chalk, or scrap of tape, do not move the pointer any more.

 

turn the engine backwards about 30 degrees, looking into the leading plug hole for the next apex seal to come to the center of the hole. The leading plug hole is the one on the bottom of the number one rotor housing. Once you have that apex seal centered make a second mark on a flywheel tooth or valley between teeth, whatever is under the pointer.

 

Half way between those two marks, make a third mark. This mark will be the TDC mark, accurate to about a degree. Clean the tooth with a fine file and paint it red. Count the teeth on the flexplate/flywheel.

This puts the apex seal at TDC.  What we want is the combustion chamber at TDC. The center of the indent on the rotor face is 60 degrees from the apex seal.  Rotating the E-shaft 180 degrees puts the rotor face at TDC.

 

Let us say that you find 106 teeth. divide 360 by 106 and get 3.39 degrees per tooth. So, for a timing mark at 24 degrees (for example) you would count off 7 teeth while turning the engine backwards. Mark whatever is under the pointer a different color than red. Make it bright like white or yellow. You can move the red dot back under the pointer. Remove the wire pointer and make up a permanent pointer to point at the red mark. So long as the engine is not turned during this process, all will be well. If you install more than one timing mark stamp what each is for on the spacer plate, with the correct paint dot by each line. 

 

Use only a clip on inductive timing light. clipped onto the leading plug wire of the number one rotor housing. 

 

Lynn E. Hanover

 

 

Good point. That 25 number it turns out was how many years ago I could remember anything.

 

So this morning I went out and assembled some pieces and took pictures. I used a late 12A rotor housing. 

 

13B and Renesis rotor housings will/may be different.

 

The stock housing has the apex seal over the leading (bottom hole) at 118 degrees Before Top Dead Center.

 

The apex seal is centered over the trailing (upper plug hole) at 100 degrees After Top Dead Center. ATDC

 

So the crank would be turned 218 degrees (in this case) in order to see the two apex seals. Also this gave me an error of 9 degrees in the advanced direction. The original question from years back had been how to start a fresh engine so the distributor or crank angle sensor had been removed and reinstalled. So this is close enough to get any rotary to start and run. Ideal for distributor engines, with the rotor button pointing at the number one plug wire, just drop it in.

 

Over the years Mazda has moved the plug holes up and down and increased and decreased the distance between them. Mostly so they can sell cars in the Peoples Republic of California.

 

So this system gets you a different result based on the iteration of engine years

 

I determine TDC with a fixture and dial indicator with the engine apart. Pictures and instructions available for free.

 

For assembled engines if you are after deadly accurate timing marks, In order to tune the engine, here you go.

 

Make up an empty plug. Use an old Non Mazda plug. With a big punch drive out the porcelain. Push in a length of plastic (Food Grade) hose from Sears. Seal with silicone. Remove the trailing plug and squirt in some motor oil. Turn the engine over a few times to wet the side seals with oil. Turn the engine to the position you suspect is close to TDC number one housing. Screw in the special plug into the trailing hole. The top hole of number one housing.

 

If nobody is around to watch you, put the end of the hose against the under side of your tongue

 

Gently rock the engine back and forth over TDC. Notice that there is a distinct null where there is no suction, but the slightest movement in either direction generates suction. That null is TDC within about one degree.

 

Or if this seems gross to you, wipe a bit of dish detergent across the hose end and watch the film for a null.

 

Want to get closer?

 

Neck the hose down to a piece of 1/8" brake line. Connect a smaller diameter clear hose to the brake line.

 

Stick the end of the small hose into a clear container holding a small amount of ATF.   Turn the engine a bit past TDC to draw up some ATF into the small hose. As the engine turns past TDC the column of ATF stops moving higher in the small hose. That is TDC. 

 

Here is a graphic and photo of the TDC finder.

 

Lynn E. Hanover