electronic ignition

[38plymouth]

RE: 71 Bonneville with Boyer Brandson Ignition
Is is OK to remove one spark plug lead while the engine is running while tuning the carbs.
If so, should the lead be grounded or not?
Thanks
Sam

[BoschZEV]

It must be grounded or you risk permanent damage to the coil due to internal arcing.

[38plymouth]

Thanks, should I start it on one cylinder or will it be ok to pull the lead and ground it as soon as it starts?
Sam

[BoschZEV]

Thanks, should I start it on one cylinder or will it be ok to pull the lead and ground it as soon as it starts?

It's not OK to pull the lead off when running. For one thing, doing so without shocking yourself isn't easy. At a slow idle of, say, 300 rpm that coil will rise to maximum voltage 5 times if it only takes you 2 sec. to pull the lead and ground it. If the internal insulation breaks down it will form a conductive carbon track and that track will only grow in time.

If you feel brave enough to pull a lead off, but you can't start the bike on one cylinder, it would be perfectly fine to have one end of a wire connected to ground and once it was running to attach the other end of that wire to the plug cap to short it to ground. Personally, having touched the outside of a damp plug wire once nearly 50 years ago I'll never forget the experience and definitely would not want repeat it. I'd start the bike with the lead already grounded.

[38plymouth]

It's not OK to pull the lead off when running. For one thing, doing so without shocking yourself isn't easy. At a slow idle of, say, 300 rpm that coil will rise to maximum voltage 5 times if it only takes you 2 sec. to pull the lead and ground it. If the internal insulation breaks down it will form a conductive carbon track and that track will only grow in time.

If you feel brave enough to pull a lead off, but you can't start the bike on one cylinder, it would be perfectly fine to have one end of a wire connected to ground and once it was running to attach the other end of that wire to the plug cap to short it to ground. Personally, having touched the outside of a damp plug wire once nearly 50 years ago I'll never forget the experience and definitely would not want repeat it. I'd start the bike with the lead already grounded.

Thanks again. I usually shoot first and ask questions later.
Sam

[Shaky Jake]

BZ speaks the truth. Years ago I ruined a good original BMW magneto coil this way. I still feel bad about it.




Kevin

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