KG7 Scintilla coils

[Robert Neymeiyer]

Hi there, I’m moving along on my 2 Merc winter projects but I have a question, I purchased 2 coils that are NOS Mercury chainsaw coils. The secondary pin is not on the bottom. Have any of you successfully modified any of these so the plug wire can connect at the bottom? I was thinking soldering a brass strip but afraid of it grounding/arcing to the magneto plate.

Thanks!

–bob

[jeff-register]

Yes Bob,
There are several coils that fit your Bendix mag. In the past I used old military coils with the same problem or some coils have two outputs. You need to remember about 1.5″ clearance or insulate with something.
Back in the 50’s T.V.’s had an arcing problem from the high voltage flyback transformer. The industry came up with some liquid insulation called “Corona Dope” it insulates very high voltage & can be found online at M.G. Chemicals. A guy can get a small 2oz vial with an app brush for $15 or so. Also I used fiberglass cloth for model airplanes, very thin cloth. Glue the cloth on with the corona dope & sandwich with saturated cloth.
Also the secondary winding of the coil (or transformer actually) wrapped on the outside of the windings so your additional wire has the same potential as the coil so no worries.
Only thing is capacitance leakage from being close to a grounding surface. Electrical energy always has magnetic “flux” energy around the conductor. That will be a loss of energy for your spark plug but very little. Just try to keep clearances when you can.
At any rate look up M.G. Chemicals just for some data on insulating designs. Others have used it too,
Good luck!!

[jeff-register]

P.S.
Bob,
Looked it up & they use the term “dielectric” Don’t let it confuse you. It means the better the die the better the insulating factor is all.

[Robert Neymeiyer]

Makes perfect sense Jeff. I understand magnetic flux and mutual induction very well. (I teach Applied Electricity.) I will just need to insulate the secondary (plug wire) connection. It lays right on top of the insulating saddle but not covered by it. Thank you. If you can provide any other advice I would welcome it!

Have a great night. You guys are great!

[jeff-register]

Bob,
Iv’e always been interested in electrical. My Dad worked at NASA in design & built firecrackers, Me I built A bombs. There are very many that know much more than me here & wiling to help, Super site. Ever work with a neon transformer? They change voltage & current all by themselves On E bay are more coils that fit too. Use a dual fire coil for a hotter spark.
Only item that comes to mind is replace the capacitors or load test them. Let me know & I’ll send a ckt to build for testing. I have it SOMEWHERE!!!
Be very careful soldering to the output. It overheats easy.

• This reply was modified 4 years, 1 month ago by jeff-register.

[mercuryman]

Many of us have used the Military Surplus coil which is the same a chainsaw coil. Don’t use a brass strap , I use a small insulated wire and run under coil on top of rubber insulator under coil. Then I put a few strips of electrical tape on bare metal nest to coil. I have never had a problem with spark grounding. I have tested the two spark coil and single spark coil both would only jump the same size gap about .2 inch.

• This reply was modified 4 years, 1 month ago by mercuryman.
• This reply was modified 4 years, 1 month ago by mercuryman.

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