H4 magneto question

[grandpa Love]

A friend called today, has an A with an H4 magneto. He wanted to know if he can fine tune it like a distributor? Loosen the bolts and turn it back and forth to adjust the timing a bit........i may be wrong on this but I don't think a magneto works the same as a distributor. I told him to time it correctly to start with and he won't have an issue.

 

[Devin Down South]

Absolutely you can. That's the reason for the slotted bolt hole on the bottom.

 

[grandpa Love]

Absolutely you can. That's the reason for the slotted bolt hole on the bottom.

The slotted bolt hole is actually there so you can set the timing .......

 

[DaveBN]

Set the timing mark with number one cylinder ready to fire and the magneto rotated so that the top of it is as close to the engine block as possible. Then rotate the top of the magneto outward until the impulse trips, you'll hear a click sound. Then tighten the bolts. Turn the engine over two revolutions and check that the magneto impulse trips exactly as the timing marks line up.
Yes the magneto can be rotated to adjust timing but that should not be necessary and usually will cause a problem such as low power or overheating.
Dave

 

[Powered By IH]

A friend called today, has an A with an H4 magneto. He wanted to know if he can fine tune it like a distributor? Loosen the bolts and turn it back and forth to adjust the timing a bit........i may be wrong on this but I don't think a magneto works the same as a distributor. I told him to time it correctly to start with and he won't have an issue.

Yes he can.
I think it's around 300-400 RPM that the impulse kicks out, so as long as he runs it above that he should be fine.
Is that the correct way to do it? No. Can it work? Yes.
The "correct" way is to verify the impulse coupling is working correctly, points are set to the correct gap, and it is timed to trip at or right after TDC. As you probably know, those can all affect timing.

 

[grandpa Love]

Set the timing mark with number one cylinder ready to fire and the magneto rotated so that the top of it is as close to the engine block as possible. Then rotate the top of the magneto outward until the impulse trips, you'll hear a click sound. Then tighten the bolts. Turn the engine over two revolutions and check that the magneto impulse trips exactly as the timing marks line up.
Yes the magneto can be rotated to adjust timing but that should not be necessary and usually will cause a problem such as low power or overheating.
Dave

 

[grandpa Love]

Yes he can.
I think it's around 300-400 RPM that the impulse kicks out, so as long as he runs it above that he should be fine.
Is that the correct way to do it? No. Can it work? Yes.
The "correct" way is to verify the impulse coupling is working correctly, points are set to the correct gap, and it is timed to trip at or right after TDC. As you probably know, those can all affect timing.