Hi Paul and All

On the issue of TDC, where is it on a rotary?
At min chamber position (max compression)?

Steve Izett
Perth WA
Building Renesis 4 Port Glasair SIIRG

It is when the front rotor has minimum chamber volume
adjacent to the spark plugs.

It can be detected in several ways. If you fill the chamber with
oil and connect a transparent tube to the chamber through the spark
plug and slowly turn the e-shaft the oil in the tube will
rise and fall. When it is a minimum that is top dead center.

Here is another way of checking it if the engine is apart.


Paul Lamar


Thanks Paul

Steve Izett

Paul, I assume these builders are looking for the mechanical TDC point on an
engine that is not running preventing the use of the timing light. I read
recently that the keyway on the front of the e-shaft is in alignment with
the high point of the eccentric on the shaft. If this is true, then standing
a short length of keystock on end in the keyseat gives a pointer. Remember
that with the front bolt out the thrust bearing is not restrained, so no
spinning the engine with the starter etc.

george grimes