I thought I had most of my engine parts assembled and ready to install when
I saw in one of my manuals a TDC sensor.  I guess the PO did not install it
when he rebuilt the motor.  Anyway, I have the following questions.... What
is the TDC sensor? What does it plug into?  From what I can tell, it is
installed in the right crankcase half.  Are these expensive?  It seems like
every time I turn around, I find a missing part.  Any help with this
question will be appreciated.

Thanks in advance,

Scott

BTW...This is an 81 Westy.