Grounding Spark Plugs

[daveo]

It's a Good Thing to ground the high (secondary) side of the coils when cranking with plugs out, the secondary voltage needs to discharge to ground and if it can't go through the plug wire they have been known to arc right through the coil case..... electricity will arc 1" for every 1000V, so a coil that puts out 35KV can do some arcing and damage

[argonsagas]

Oh. The place I read it was from was an old Clymer manual for GS 400's from 1977-1978.

But I'll believe you guys anyday.

Bottome line is that if I want to be real careful, I can get a friend to ground the other plug.

Great idea.....it gives you a check on the output of the coil, as well. Just get the friend to hold the wire with one hand, without the plug, and have him place his other hand on the engine as you turn on the starter.


Even better, do this with the love of your life......just wait until you see the 35K spark in her eyes.

Of course, knowing an average woman's temperament, that may be the last thing you see for a while...... 8O 8O :roll:

If you plan to do this, be sure to send us an address for the get-well cards.

[UncleMike]

To be more specific, I think I'll clamp both plugs to the fins when checking compression.

[jimcor]

[quote="earlfor"]Spring clamps are just metal clamps that resemble a giant clothespin. You can buy them at any hardware store or home depot, etc.

Earl


...or head shop where they are called roach clips.
Another way to ground them plugs is to clip their wings when they're young, right out of the box.

I gotta stop this...

[UncleMike]

...or head shop where they are called roach clips.
Another way to ground them plugs is to clip their wings when they're young, right out of the box.

I gotta stop this...

I feel like I'm taking crazy pills.

[jimcor]

...or head shop where they are called roach clips.
Another way to ground them plugs is to clip their wings when they're young, right out of the box.

I gotta stop this...

I feel like I'm taking crazy pills.

Relax, that's normal. 8O

[Anonymous]

Unclemike, yer startin ta scare me! 8O

[Hotblack]

You could also..... disconnect the juice to the coils instead of grounding the plugs, the plugs should be right under the gas tank.

I was putting a new carb on my car once, and flushing the fuel pump out by letting the line shoot into a metal mixing bowl placed under the hood. Of course you don't want the car to run while doing this, so you need to disable the ignition, they say to disconnect the hot lead to the coil, but of course I couldn't be bothered with that so I just yanked the secondary lead and left it well away from the bowl (at least a foot). While cranking the motor I heard a "snik snik snik" sound; just as I was thinking "hey that sounds like the sound of electricity ar - POOF! the bowl went up! I got the fire out, but only after a) grabbing the fire extinguisher from inside the car, pulling the pin and.. the pin breaks off in the trigger rendering the unit as useless as *@%^$*@%^$*@%^$*@%^$ on a boar :x The running at light speed into the kitchen and returning with THAT fire extinguisher. This all happened in probably ten seconds. Anyway what was the point of this story? Oh, just how far coil voltage can arc.

[Anonymous]

People too often under estimate the volatility of gasoline fumes. :roll:

[Hotblack]

Yeah, once was enough for me.

[Anonymous]

The bike is going to start on you if you've got the other 3 plugs connected. You're checking for spark and if they spark it will start :roll: .

Steve

[UncleMike]

I've only got two plugs in mine.

I'm checking for compression.

[argonsagas]

I've only got two plugs in mine.

I'm checking for compression.

Mike....remove all plugs before you do a compression test.

Connect the plugs to the wires and sit them on the head or any other metal part of the bike.

It does not matter if they are clamped there or not.

You turn the engine over for 3 seconds for each cylinder.

(You gain nothing by doing it for a longer time.)

When doing the test, hold the throttle wide open.



There are no other major concerns.

[UncleMike]

Perfect.

[saaz]

Agree with argonsagas. I always remove all plugs to reduce the load on the starter and get consistent results. Ground out the plugs, as the voltage from the coils will try and go somewhere.

Don't check compression too much otherwise you may worry