I have been having a fun weekend trying to get a reliable spark out of my mag for my D318 off my d6 I just put the clutch in was planning to test the clutch. the mag that comes off it is a bosch MJK 4/2 360C-410. I can only seem to get a weak spark not much more than a1/8". I changed the points setting from .014-.018 and everywhere in between. the only thing I haven't change is the coil. could I steel a coil out of an MJK 4/2 180B-311?  they are both of the 3A serial numbers. the right mag should be part number 7F9937 for the bosch MJK?  Does anyone have the part number change over of parts number to make and model of other mags? would the inside of a d2-d4 pony be the same as coil size or parts?  

is the spark nice and blue or is it yellow. i was told they only like the factory points gap. but try increasing the plug gap slightly say 28thou instead of 25. also clean and lighty file dress (if needed) the mating surfaces for the mag and clean the plug seat area rub a little 2b graphite pencil on them it will help with the return path giving better spark. a old mechanic showed me and it does work hell it might just put off that mag rebuild a bit longer.

Clean the inside of the cap. Dirt or carbon from use can cause a late/weak spark cuz the spark is going everywhere inside the cap.Only use copper plug wires. The gap in the points and the gap in the plug AND the gap in the cap/button needs to be clean and free of whiskers (debris). One thing that has got me more than once is the fiber contact of the points on the cam lobe on a mag/distributor gets dry from setting and will shorten itself in just a few revolutions changing the point gap instantly.

mog5858 wrote:

 I have been having a fun weekend trying to get a reliable spark out of my mag for my D318 off my d6 I just put the clutch in was planning to test the clutch. the mag that comes off it is a bosch MJK 4/2 360C-410. I can only seem to get a weak spark not much more than a1/8". I changed the points setting from .014-.018 and everywhere in between. the only thing I haven't change is the coil. could I steel a coil out of an MJK 4/2 180B-311?  they are both of the 3A serial numbers. the right mag should be part number 7F9937 for the bosch MJK?  Does anyone have the part number change over of parts number to make and model of other mags? would the inside of a d2-d4 pony be the same as coil size or parts?  

Humm good question....  Looking... at firs glance I'm thinking so but let me look later tonight..

Get a resistance reading on the coil secondary, should read approximately 6200 ohms.
Yes, coils are interchangeable.

thanks for all the great info. I will let you know what I find. I will say I never thought to check the spark plug gag.

check the simple things first it can save you a lot of time and money. and stop you looking like a fool.

 after I got my head out of the clouds and got things timed right well I hope. I did not find the MAG marking on the pony flywheel at first only the TDC mark and had timed it to TDC and not MAG. the pony motor running for about 45 seconds -1 minute then died.  so checking things I could see it sparking out inside the mag.  so I pulled the coil back out and you can see where it been leaking spark out the front. after changing it out for another coil from a parts mag I now have a good spark that will jump 3/8 when you trip the impulse.  it starts and will idle low nicely but is rich and will not rev up when I try to rev it up it pops and backfires. it still is very rich as I see black smoke from the exhaust. I went through the carb last weekend in the drilling out the brass plugs and making sure everything was clean with a pipe cleaner. but still runs very rich. I think I still have a timing problem and not a fuel. when I had the pony running last year it would not turn much more than 1/2 max rpm but was able to get the main fired off with a little summer in a can. I can roll over the pony flywheel and hear the impulse fire when TDC comes up to the top each time for both cylinders. I could try moving the timing gear a tooth the two M's will never meet up when turning 44 teeth and an 18 to re time all the timing gears I will have to pull the pony to get the side plate off. one side not is the pointer is missing off this pony motor so I was using eye reference to where it should be from some of my other ponys and what the serviceman reference shows in pics.  I know this maybe doesn't make much sense and should be simple and straight forwards but this welder playing mechanic needs help. 

Hi
to re-time the M marks carefully remove the circlip holding the tang slotted magneto drive gear on to it's shaft, remove the gear and reinstall it aligning the M marks, reinstall the circlip and you should be good to then install the magneto after first aligning the chisel mark on the magneto arrester plate/body and the mating chisel mark on the coupling/tang drive--as outlined in the grey Operation and Maintenance Book.
Cheers,
Eddie B.

Hope you're still having fun...