F12 magneto timing

[martinautry]

I usually have trouble finding the timing mark on the bell housing so I usually crank the engine to where the number one piston is at max position on the compression stroke. Then I set the magneto to that engine position. Is the timing mark usually appear at the max number one piston position?

 

[rustred]

I usually have trouble finding the timing mark on the bell housing so I usually crank the engine to where the number one piston is at max position on the compression stroke. Then I set the magneto to that engine position. Is the timing mark usually appear at the max number one piston position?

exactly , thats how its done, at top dead centre. and what unit is this on ?

 

[Fritz Maurer]

Among other things, it says "1-4 TC" on the rim of the flywheel. To be positioned at the center of the hole in the bell housing. Hard to see in bad light. Wipe the marks on the flywheel with gasoline, then paint the area with a paint marker. Reach in there with sandpaper on a stick and sand off the excess. The lines can then be easily seen and you will be able to time with pin-point accuracy.

 

[Fritz Maurer]

Unless you're using a dial indicator on the piston, you can still be off about 10⁰ either side of TC, before the piston moves noticeably, if gauging this by eye.

The danger in this is, if the impulse snaps on the advanced side of TC, you have lost a large degree of safety that the impulse coupling provides by winding the impulse spring as the engine approaches TC, and tripping at a point where it is impossible for the engine to kick back. The timing coupling is capable of ridiculously minute timing increments. There is no reason that ignition should be anything but spot-on.

It makes no difference what position the spark lever is in ; the spark occurs when the coupling trips.

The spark lever is not operational until the engine speed is sufficient to keep the impulse coupling disengaged.

 

[martinautry]

F12