MTFCA Forum

Currently disassembling the Bosch DU4 magneto and came up with some questions.

The instructions all over the internet don’t include this info it seems; but when reassembling, how do you align the gears? I notice there’s an A and C which I assume is clockwise and anti clockwise, and there’s an A and C on the interrupter housing. I’m guessing when the cutout on the interrupter is over the A or C that’s the alignment there, but where do I turn the distributor gear so that they correlate?

Second question is in regards to timing while driving. I notice on the forum there are those with a linkage to adjust timing on the fly like a normal spark control, and those that do not have them (They have the arm on the magneto…but no linkage on the car.). So is it as imperative to adjust spark while driving like original, or is a DU4 more of a set it where it works best and get away with it? With the side drive I’ll most likely use my starter a lot, but I still want to be able to hand crank if necessary.

It’s cleaning up nicely:

Also here are some pics of linkages and such I found searching for reference. Also, I’m curious how I will run wires with my headers in building :

Page 23 here:

https://oldcroak.com/magneto-service-ma ... osch-1928/

Being able to adjust the advance while you’re driving is a good thing.

John E. Guitar wrote: ↑

Fri May 20, 2022 8:49 am

Page 23 here:

https://oldcroak.com/magneto-service-ma ... osch-1928/

Being able to adjust the advance while you’re driving is a good thing.

Man I looked everywhere on that website I can’t believe I missed that! Thank you, that’s going to be very helpful when I reassemble!

Idk how I will get a linkage for the timing advance though, especially with race headers, not mention I may need longer spark plug wires. Perhaps I can reroute throttle to over the block like the adaptor for a model A to use NH, and use the hole in block for the timing somehow.

Jacob,
I believe your timing rod still come around the front of the block, similar to the
conventional Model T timer. There should be no need to re-route that.
Harry

Indeed, I think I can make something relatively easy after looking at a lot of pictures with some bolt on parts! First thing is to get the mag working well lol.