"Mike wrote:

Here are a couple of photo's of Eisemann coils I have here, one has been rewound by a Aussie maggie repairer, also in the photo is the patented Eddie Bedwell coil testing wire I mentioned previously, part number EB2016, I think it's time you quit spending time on that maggy and either send it off to be reconditioned or buy a reconditioned unit because the bearings in your maggy will almost certainly need regreasing for future use and a used magneto you buy will be in the same condition, needing regreasing, yes they might spark out of the shipping box but how well and for how long, the bearings on the armature will fail.

I've had 7 or 8 magneto's reconditioned since 2008 by 3 different Magneto "Experts" who charge $180 - $250 for their services, one guy I discovered simply used old parts from other magneto's and I had the coil in my "reconditioned" RC-2Q magneto fail immediately on my RD6 and I still have the blisters on my hands from trying to start that pilot motor for the first ever time for 3 or 4 hours!!! The 2nd guy was a new kid on the block who had bought a reputable magneto repair business from a older gentleman and my Eisemann G4 Edition 3 failed after just a few runs on the 2 Ton and it was obvious when Eddie Bedwell took that maggy apart that the new kid had cut corners and not done a full recondition job letting me down, and he wasn't cheap either, the 3rd guy I'm with now seems to be the best of the lot but none are perfect, bottom line is you want to be able to forget about your magneto once it is fitted to the tractor other than the occasional points clean.

If a pilot motor will not start you do not want to be second guessing if the magneto is the cause because it takes hours to get at the maggy on a D2 and D4 to file and set points and muck around, life is too short for that drama of hanging upside down in the cockpit every few months and from my experience a weak spark outside the motor when testing the spark plug will often result in no spark under compression, don't ask me why, but it is just is a sad fact of life with magneto's.
Mike

that compressed NO SPARK thing is really common w/ 2 cycle moto motors... arg and no I can't explain it either...

What would be really interesting would be to eliminate the whole distributor and use a waste spark type of coil.

I think using a neon ignition coil would make for an easy install. Probably use a ballast resistor with it, but it would be interesting.

"mcbitchman" wrote:

that compressed NO SPARK thing is really common w/ 2 cycle moto motors... arg and no I can't explain it either...

I think it's because the density of the air increases resistance across the gap.

"cojhl2" wrote:

I think it's because the density of the air increases resistance across the gap.

now that makes sense....

"Walt wrote:

Many years ago, when I was an electronic technician, one of the guys in my department wanted to determine how a spark plug behaved at compression.

He made up a block of aluminum and drilled a hole for a spark plug, threaded of course.

He also drilled a hole for air to be inserted under various pressures.

Then where the end of the spark plug was he made up a Plexiglas plate so the actual spark could be seen.

At room pressure the spark acted as expected with whatever high voltage he applied (fairly low – like 1000 volts).

But when he added high air pressure, maybe 100 pounds pressure or more, the spark took far higher voltage to arc.

That is why the usual spark plug voltage it around 20,000 volts.

Interesting Walt, thanks for that info, just what many of us have found in real life, no doubt temperature and air moisture has some influence too.
regards
Mike

Used to market a "Sparkplug Cleaning Test Kit" which had a small sandblaster setup and the other port you screwed the sparkplug in and applied air pressure to with the same small viewing window. It had a potentiometer and a calibrated voltage meter to adjust and read the "Test" voltages. The guys said it worked 50% of the time as a plug may test out good but still fail/misfire under compression with fuel added into the equation.

JMVMOPAR, your diagram is probably right? (unless its a generic Internet one, then its 50/50) I just remember a couple of old cars where we laid the coil on the manifold troubleshooting spark issues and if you watched the coil in the dark you could see sparks jumping off its case.

"drujinin" wrote:

if you watched the coil in the dark you could see sparks jumping off its case.

That's interesting. If the field windings were grounded to the case, it shouldn't ever loose ground and therefore never create spark. I could see it sparking if the plug wire wasn't hooked up and it was arching through the case.

drujinin;189044 wrote:

Used to market a "Sparkplug Cleaning Test Kit" which had a small sandblaster setup and the other port you screwed the sparkplug in and applied air pressure to with the same small viewing window. It had a potentiometer and a calibrated voltage meter to adjust and read the "Test" voltages. The guys said it worked 50% of the time as a plug may test out good but still fail/misfire under compression with fuel added into the equation

That is exactly what my father had in his auto repair shop in the 50's--one of the jobs my brother and i did was pull spark plugs,sandblast and gap them, and then check them for spark--back in those days plugs always needed cleaning as they would carbon up quite bad