I had a mag on a DW21 pup engine that wouldn't fire unless it was turning over very fast. The impulse drive was not working and it was a real pain until I replaced the spring inside. You mentioned using a drill, it should fire turning it by hand, once the latch releases. I just scrapped a rough old 200 Lincoln welder because of no spark and it was just a sticky latch on the mag drive. Maybe I'm barking up the wrong tree but I thought I'd mention it.Phil

Hello Phillip
Any ideas are most welcome.I think that the mag needs to be remagnetized as you need a good magnet to get the high voltages required to produce a good spark.It produces a fair spark when coupled to a battery drill,but should as you state produce a spark when turned by hand.As I have replaced most parts, it points to the weak magnets.
What do you think.
Cheers
Martyn

You didn't mention if the impulse coupling was working or not, or if your mag has one. I found my Servicemens Reference book which details complete disassembly of the mags used on the D326 and D337 engines.

It states "The primary function of the impulse coupling is to permit the ignition spark to be intensified at low rotative speeds in order to facilitate engine starting without the aid of an auxiliary ignition system. Through its construction, it also automatically retards the ignition spark during the starting period, reducing the possibility of damage to the engine or danger to the operator by back firing. It automatically disengages when the magneto reaches a speed of 180 RPM and then acts as a positive drive only".

I believe it should latch twice for every revolution it takes(2 cyl) and may require an adjustable wrench to complete the turning process. If you take your coupling apart remember the orientation of the parts. Phil

Checked my parts book on impulse coupling,it does not have one. Will get the mag serviced as to remove it,or to even remove the cap,the fuel filter assembly has to be removed. Bit of a pain.
Has any one replaced a wire pull start cord on one of these machines,mine has snapped 4 inches from the pull handle?
Martyn