Grounding the head

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acadian

acadian

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Question for those of you running a DT alloy head steady, what's your solution for grounding to the head?
 
I have one of JimC's alloy ones, and I ran a common ground all the way back to the battery.
 
gortnipper said:
I have one of JimC's alloy ones, and I ran a common ground all the way back to the battery.
Click to expand...

From the head steady mount or between the head and the steady itself?
 
To one of the front capscrews that holds the spring assembly mount to the headsteady (one continuous wire goes from headlight shell, to frame at coil mount, to headsteady, to battery, to taillight).
Ta.
 
To get away from the vibration that commonly breaks the wires connected to the head, I would suggest running a new wire from one of the oil filter attaching bolts up to the ground connection in the battery box.

Just tape the wire that went to the head back to the harness, out of the way. It just goes back to the ground connector in the battery box and forward to the headlight shell. Jim
 
comnoz said:
To get away from the vibration that commonly breaks the wires connected to the head, I would suggest running a new wire from one of the oil filter attaching bolts up to the ground connection in the battery box.

Just tape the wire that went to the head back to the harness, out of the way. It just goes back to the ground connector in the battery box and forward to the headlight shell. Jim
Click to expand...

Spark plugs need a direct and good connection to the head and the head directly into the earth circuit. Oil filter bolts are separated from the head by a multitude of joints, gaskets, maybe paint, etc. If vibration is a problem for the shop-bought earth wire to the head then add a dedicated wire with a single loop into the wire (the loop absorbs the vibration between the head and frame/earth ).
Ta.
 
acadian said:
Question for those of you running a DT alloy head steady, what's your solution for grounding to the head?
Click to expand...


I used one of the suspension spring bracket bolts.

Grounding the head
 
needing said:
comnoz said:
To get away from the vibration that commonly breaks the wires connected to the head, I would suggest running a new wire from one of the oil filter attaching bolts up to the ground connection in the battery box.

Just tape the wire that went to the head back to the harness, out of the way. It just goes back to the ground connector in the battery box and forward to the headlight shell. Jim
Click to expand...

Spark plugs need a direct and good connection to the head and the head directly into the earth circuit. Oil filter bolts are separated from the head by a multitude of joints, gaskets, maybe paint, etc. If vibration is a problem for the shop-bought earth wire to the head then add a dedicated wire with a single loop into the wire (the loop absorbs the vibration between the head and frame/earth ).
Ta.
Click to expand...


Where did you get an idea like that? The tiny amount of spark currant is not affected by the length of the path. Jim
 
Is this really necessary, I have never had a grounding lead from the head on any of by bikes. Grounded the engine elsewhere but not on the head. ??? Never had an issue.
JUG
 
jug said:
Is this really necessary, I have never had a grounding lead from the head on any of by bikes. Grounded the engine elsewhere but not on the head. ??? Never had an issue.
JUG
Click to expand...
Yes, this is just a matter of convenience because it's up under the tank near assessable wires and what not. You mention any of your bikes. I only know of this issue being one of the many Commando's issues, with the engine being isolate by it mountings.
 
comnoz said:
Where did you get an idea like that? The tiny amount of spark currant is not affected by the length of the path. Jim
Click to expand...

Oh dear.
Of course resistance increases with path length (high school physics)!
Ideally, the earth should be to the spark plug body (ugly). Less ideal, to the head itself (more discreet). Even less ideal, to something that bolts metal to metal to the head. Worst scenario, to the engine cradle potentially separated by, say, coated composite head gasket, thread lubricated head bolts, paper barrel gasket, grease/oil/paint/powdercoat between cradle and engine joints, oil/grease/paint/powdercoat under the oil filter mounts, etc. The spark plug has enough air gap resistance to overcome without adding more via a convoluted earth pathway.
Ta.

My earth is like L.A.B.s. His wording is succinct.
 
needing said:
comnoz said:
Where did you get an idea like that? The tiny amount of spark currant is not affected by the length of the path. Jim
Click to expand...

Oh dear.
Of course resistance increases with path length (high school physics)!
Ideally, the earth should be to the spark plug body (ugly). Less ideal, to the head itself (more discrete). Even less ideal, to something that bolts metal to metal to the head. Worst scenario, to the engine cradle potentially separated by, say, coated composite head gasket, thread lubricated head bolts, paper barrel gasket, grease/oil/paint/powdercoat between cradle and engine joints, oil/grrase/paint/powdercoat under the oil filter mounts, etc. The spark plug has enough air gap resistance to overcome with adding more via a convoluted earth pathway.
Ta.
Click to expand...


So check the currant flow over a spark gap. Then measure the resistance from the head to the rear of the cradle. Find out how many volts drop there will be.

By the way, Check the resistance of the path through the original ground wire on the head to the ignition coil. See if you can find a gauge accurate enough to measure the difference in the two paths. Jim
 
Hi Jim.
Agreed. Difficult to measure at fresh assembly but a cold, wet, miserable night 150km from anywhere will find a failure in your earth path soon enough. It is difficult to gauge your path in these circumstances: to the head or headsteady - easy.
Ta.
 
Neither the head nor any part of my engine is grounded to anything.

What am I missing, and why does everything electrical function perfectly for many years now without this grounding?
 
1up3down said:
Neither the head nor any part of my engine is grounded to anything.
What am I missing, and why does everything electrical function perfectly for many years now without this grounding?
Click to expand...

That first sentence is a mystery that defies science on this planet.
Ta.
 
needing said:
Hi Jim.
Agreed. Difficult to measure at fresh assembly but a cold, wet, miserable night 150km from anywhere will find a failure in your earth path soon enough. It is difficult to gauge your path in these circumstances: to the head or headsteady - easy.
Ta.
Click to expand...


Actually, if the wires broke off the head you wouldn't even notice a difference in the way the engine ran. There is going to be enough engine grounding though the the cables and chain or the proximately of metal parts to complete the ignition circuit -even if the spark needs to jump a gap of a mm. Of course if the engine was completely isolated and the spark was jumping a gap somewhere from the engine to the chassis you might get a surprise when you touched the engine.

But if both red wires separate from the eyelet then you might loose the grounding in the headlight shell. Jim
 
1up3down said:
Neither the head nor any part of my engine is grounded to anything.

What am I missing, and why does everything electrical function perfectly for many years now without this grounding?
Click to expand...


Well if you have two separate ignition coils then all you need is enough ground to flow around .02 to .05 amps. A drive chain or clutch/throttle cable will easily supply that.

If you have a single coil then you don't even need that to run correctly -although a ground would be a good idea to prevent electronic ignition module damage if you have an open plug wire. Jim
 
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