Checking the timing diagrams for my Westbury Seagull engine
it seems ETW did not take into account the fact that this is a désaxé (desaxe, if the e-acutes does not come out on your screen) design. Is Top Dead Centre when the crankpin is at the top or when the piston is at its highest point (3.42° later)?
this is awquard to answer without the instruction sheet
here's the definition of TDC
In a
reciprocating engine, the
dead centre is the position of a piston in which it is farthest from, or nearest to, the
crankshaft. The former is known as
top dead centre (
TDC) while the latter is known as
bottom dead centre (
BDC).
More generally, the dead centre is any position of a
crank where the applied force is straight along its axis, meaning no turning force can be applied. Many sorts of machines are crank driven, including
unicycles,
bicycles,
tricycles, various types of
machine presses,
gasoline engines,
diesel engines,
steam locomotives, and other
steam engines. Crank-driven machines rely on the energy stored in a
flywheel to overcome the dead centre, or are designed, in the case of
multi-cylinder engines, so that dead centres can never exist on all cranks at the same time. A
steam locomotive is an example of the latter, the connecting rods being arranged such that the dead centre for each cylinder occurs out of phase with the other one (or two) cylinders.
with this example TDC is wrong
In a
reciprocating engine, top dead centre of piston #1 is the
datum point from which
ignition system measurements are made and the
firing order is determined. For example,
ignition timing is normally specified as degrees
before top dead centre (
BTDC) although a very few small and fast-burning engines require a spark just
after top dead centre (
ATDC
with this one it should be top center only
I would say if he's talking about ign timing what you have is good before TDC