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Slick magneto dimensions

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Flyguyeddy

Well-Known Member
Joined
Jun 9, 2018
Messages
440
I am looking for the dimensions of the common slick 4300 series mag used on these volkswagens.

I need the mounting depth from the flange to the face of the impulse coupling, basically how deep it mounts into an accessory case. I want to make a magneto drive for my 4220 magneto.
 
Trying to get this to work. Need to know what the dimensional difference is between the 4300 and the 4200

https://imgur.com/gallery/WqwDfsY
 
The Slick manual is floating around on the internet somewhere. Maybe it has the dimensions. I downloaded it a few years ago but don't have access to that computer at the moment. I'll look when I get the chance.

Ed
 
I measured my spare 4316, and the distance from the mounting face of the mag to the front face of the impulse coupling is 1.062". The tangs on the impulse coupling add another 0.226" or so. Externally, I don't think there is much different dimensionally between a 4216 and 4316 mag.
 
Awesome, thank you Fred. The magneto i have is a 4220 military surplus unit that is found on air cooled generators. I had to open up the bore of the mount to get it to fit, and it is visually much shorter than the pictures of the 4316 i can find on the net. Scott casler of hummel engines has been using these magnetos for 15 years he says with no issue.
 
The only "problem" with the 4220 mag is that its impulse has only 15 degrees of lag, while the 4216 and 4316 mags have 25 degrees of lag. So, if you set the timing at 28 degrees BTDC, the 4220 impulse will fire at 13 degrees BTDC rather than 3 degrees BTDC. This can be a problem if you are hand propping. Marty Roberts, who used own Great Plains Aircraft Supply before he died, would remachine the 4220 case to move the impulse stop pin so that it would end up with 25 degrees of lag.
 
If he just moved the pin, that doesnt seem all that hard to do. Is it really necessary though?
 
It is if you are going to set the timing at 28 degrees BTDC, and hand prop it. If the impulse fires the engine at 13 degrees BTDC, the prop can snap backwards and hit your hand. Don’t ask how I know (it really hurts).
 
I had Marty set the timing on my 4220 to 25 deg so impulse fires at 3 deg BTDC. I've got about 45 min of engine time and it's working very well. My only issue on initial start-up was that the numbering of the wires from the magneto per the GPASC instructions wasn't correct. To get numbering right, I removed the spark plugs, and, with wires attached, laid them on top of the engine so I could see which plug sparked as I hand-turned the prop through TDC. I renumbered the wires, reinstalled them and the engine started right up.
 
Related to the impulse timing modification, I found this posted on Nov 17, 2013 on the Eaglers Nest, a forum for the Legal Eagles.

I tried to copy/paste it directly here, but the graphics did not show. So, I made it into a pdf and attached it.

Hope it comes through properly, and that it helps.

Tom H
 

Attachments

  • Slick Impulse Mod.pdf
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