02-07-2017, 09:37 AM
Here is how you set up the ignition without a degree wheel, dial indicator, protractor etc. Start with a five degree flywheel and an un-modified coil. Install the flywheel and then install the coil using a .012 spacer between the coil legs and the section of the flywheel with the magnets. With the coil leg screws slightly loose, rotate the flywheel/coil (they are stuck together by the magnets) in the clockwise direction to take up all the slop in the coil mounting slots and tighten the screws. Remove the shim and hook up your simple continuity tester for a timing light and check the timing by comparing the position of the raised line on the flywheel between the two magnets with the center leg of the coil. Adjust the points to cause the timing light to go off/on when the line on the flywheel lines up with the left edge of the center leg of the coil
For 99% of all Mac engines starting with the Mac 90/100 models and later, that setting is going to be 24 - 25 degrees BTDC if checked with any of the more precise tools. It is possible to get a goofy part from time to time... I have about 60 Mac flywheels here and I've probably checked another 40 over the last ten years and I have only found one factory screw up... I have a 9 degree flywheel and the key slot has not been messed with.. It is just a bad part.
I've played with static settings from 20 to 30 degrees btdc and have never found anything that works better than the 24/25 setting I described above. I have gone to great lengths to find ways to get a few ounces more spring tension but it was a waste of time too.
I usually get around 16 ounces out of the 91 style points and up to 20 from the 101 type. Both of those settings are plenty. Make sure to sand the point contacts to have a good clean contact across at least two thirds of the surface and you are good to go.
Use an Autolite AE901 or equivalent spark plug if you can find one... I think the current number is 411.
If you stick with the system I just described you will never hurt your motor with an ignition based tuning problem nor will you ever give up any meaningful performance gain.
Now... go work on the carb... that is where all the magic is anyway
Steve O'Hara
For 99% of all Mac engines starting with the Mac 90/100 models and later, that setting is going to be 24 - 25 degrees BTDC if checked with any of the more precise tools. It is possible to get a goofy part from time to time... I have about 60 Mac flywheels here and I've probably checked another 40 over the last ten years and I have only found one factory screw up... I have a 9 degree flywheel and the key slot has not been messed with.. It is just a bad part.
I've played with static settings from 20 to 30 degrees btdc and have never found anything that works better than the 24/25 setting I described above. I have gone to great lengths to find ways to get a few ounces more spring tension but it was a waste of time too.
I usually get around 16 ounces out of the 91 style points and up to 20 from the 101 type. Both of those settings are plenty. Make sure to sand the point contacts to have a good clean contact across at least two thirds of the surface and you are good to go.
Use an Autolite AE901 or equivalent spark plug if you can find one... I think the current number is 411.
If you stick with the system I just described you will never hurt your motor with an ignition based tuning problem nor will you ever give up any meaningful performance gain.
Now... go work on the carb... that is where all the magic is anyway
Steve O'Hara
Dave L.