Briggs FH Coil Issues Still

[Havasu Dave]

Background: I got the motor running, but cycled the kill switch a bunch of times to keep it from overspeeding while attempting to adjust idle down. Engine died, wouldn't restart, no spark. I assumed I'd fried the coil by cycling kill switch. (No points/condensor)

Ordered replacement coil, adjusted flywheel gap to .010 and still no spark. Verified spark plug as good with another motor. Kill switch wire disconnected.

I checked continuity from the kill wire tab on the coil to ground. It is grounded via the case of the coil mount with no wire on it. Both coils are like that. I thought the act of grounding that tab via kill switch was what caused the coil to stop making spark.

Am I missing something here? Am I supposed to cut whatever piece of copper is shorting the tab to the coil frame to electrically isolate it? Such a simple system, but it's kicking my ass. Thanks in advance for any enlightment on the subject.

 

[Neck]

Do a continuity test with an OHM Meter from the spark plug lead to ground then one from the spark plug lead to the kill wire lug

 

[Havasu Dave]

Do a continuity test with an OHM Meter from the spark plug lead to ground then one from the spark plug lead to the kill wire lug

Thanks Neck, coil reads 4.8K to both the case and the ground lug, both of them, "but" I just put it back together with the new coil and got it started.

Also got a PM from 125crazy who informed me that billet flywheels require a little more tolerance (gap) so I need to push it out to .030 and try. I'm going to do that. I hear a noise coming from somewhere in the shroud, but at least I got it running.

I am going to assume the first coil died when it vibrated too close to the flywheel, but is in fact still a good coil.

Weird that the kill switch lug would be shorted to case ground, yet require a switch to ground to kill the coil. What's sad, is that I was an aircraft electrician for 30 years and am still baffled by a one-wire system! LOL!

 

[Havasu Dave]

Just adjusted to .027 (tried for .030) and it purrs like a kitten! Not sure on the original coil issue, but it's running, so I'm going to drink beer and stare at the chain and tensioner I need to install. :thumbsup:

You smart engine guys- don't sell these hotrod engines to the likes of me, because I have a hard time knowing what the hell to do with them! Thanks for your patience 125cc!

 

[old-timer]

Lol, It's always the somewhat simple things that kick our butts. I've had many similar things happen to me and I spent years building Briggs FH open motors for kart racing :shrug:

Glad you got it figured out ok :thumbsup:

Vic

 

[Neck]

Weird that the kill switch lug would be shorted to case ground, yet require a switch to ground to kill the coil. What's sad, is that I was an aircraft electrician for 30 years and am still baffled by a one-wire system! LOL!

Technically, it's not shorted, but connected to it by a really long piece of wire wrapped around an iron core, thus the 4.8k ohms. A short would read 0

 

[Richard Trotter]

sometimes it's just a bad ground. Make sure the surface on the posts are clean and the bolts aren't corroded.

 

[Havasu Dave]

Thanks guys, if you read above, I got it. Clearance was too tight for an aluminum flywheel, and most likely was barely rubbing enough to ground out the coil.

The back of the coil has a tab that is used for wiring the kill switch to ground. It was "that" tab that was shorted (0 Ohms) to the case, and when installed to the motor, grounded to the frame. I'll measure the coil again later to ensure I kept the meter on the right scale, or if indeed I was reading through the coil windings and seeing a zero because I was at the 20K ohm scale.

Thanks again for the input. :thumbsup:

 

[Bill Ellerby]

Hey Havasu Dave thats why we called electricans in the Navy "lighting rods", a one wire with negative potential.

 

[Havasu Dave]

Hey Havasu Dave thats why we called electricans in the Navy "lighting rods", a one wire with negative potential.

I would have been what you call an "AE" on the USMC Herks. Yep, a one-wire and a jar head! LMAO! After I retired, I worked ten years for the DOD as an electronics tech doing proprietary PC boards, radar, satcom, etc. So yeah, it figures a ONE WIRE system would kick my ass! :thumbsup:

 

[Bill Ellerby]

Don't feel bad I was a "nose picker" for the navy for 26 years and an aircrewman for 20. Now I'm just a retired grandpa with 7 grandchildren.

 

[Havasu Dave]

Don't feel bad I was a "nose picker" for the navy for 26 years and an aircrewman for 20. Now I'm just a retired grandpa with 7 grandchildren.

:thumbsup: We've lived parallel lives! I did a lot of flying as crew throughout Asia. Also retired. I miss the travel, but not the job. Lots of friends in the P-cola area, a few of them were with the Blues.