Truly meaningful TDC should be when the volume of the respective chamber is
 > at
 > a minimum IE when the flank of the rotor is up against the minimum radius
 > portion of the chamber. BDC should be when the chamber volume is maximum

--      flank

 > facing the max dimension. From TDC to BDC in a piston engine is obviously
 > 180 crank degrees. The equivalent travel of the eccentric shaft is less
 > obviously
 > 270 degrees - Just what degrees are being used in the quoted
specifications?
 > Vance J

I have a spark plug shell with a piece of brake line tubing soldered into the
center.
I build one rotor face and pack the apex, side and corner seals with bearing
grease. I press a piece of clear plastic tubing over the brake line tube. I
mount the engine "plugs up" (sorry) and fill the chamber full of ATF. With
the crank a bit off of suspected TDC. I have a piece of yard stick clamped to
the engine to support the plastic tubing. I rotate the crank to and past TDC.
I mark the highest point the ATF has gone in the plastic tube. I make another
mark on the tube about 1 inch below the maximum mark. The exact location is
not important. I rotate the engine until the ATF retreats to the lower mark.
I mark with a marker pen on the degree wheel under a temporary pointer (a
piece of welding rod). I rotate the engine back through TDC until the ATF is
again at the lower mark, and again mark the degree wheel under the pointer.
TDC is now half way between the two marks on the degree wheel. Count off the
number of degrees between the two marks and divide by 2. Make another marking
pen mark at that location on the degree wheel. Now turn the crank to move
this third (center) mark directly under the pointer. The engine is now
sitting dead nuts on TDC. Now loosen the nut holding the degree wheel in
position and rotate only the degree wheel until the TDC mark on the degree
wheel is under the pointer. tighten the nut (bolt). Now both the crank and
the degree wheel are at TDC.

   The reason for the rocking across TDC and making two marks instead of just
finding TDC with the oil column is because there is some dwell around TDC
that could allow some movement without moving the oil column.

    Now sight down across the stock pointer at the pulley you will be using.
There should be a mark or a notch with white paint in it to indicate TDC. If
not make a mark in line of sight of the stock pointer now with a triangular
file. Turn the engine backwards (counterclockwise) until the advance you want
to run is showing on the degree wheel. Maybe 25 degrees. Make another mark
and fill it with orange paint. Or whatever color your wife selects for you.
You could make additional marks with different colors at 20 and 30 degrees.
That way you can get a good guess going if you want to try a different timing.

 1. The bigger the diameter of the degree wheel the more accurate this comes
out.
 2. You only need to do this once, unless you change pulleys, or if you
change cranks. But the indexing of the keyway is very well done and is
probably OK.
 3. This sounds ten times more complex than it is.

Lynn

 
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