Grounding the Motor

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highdesert

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Jun 17, 2009
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Grounding the motor to the frame has invariably resulted in vibration fracturing the connection for me.

I am interested in some suggestions, pictures would be very helpful.
Thanks
 
How about a grounding strap instead of a wire. We use thick braided wire or straps on aircraft, to prevent such an occurance.
 
I would suggest a ground wire from one of the oil filter mounting bolts up to where the battery ground wire goes- usually under the rectifier mounting bolt. Why put a ground wire to the head when that is the area of most movement and vibration. There is very little vibration at the rear of the cradle and the wire is hidden and doesn't fail Jim
 
Jim, I like that idea!

And I have no idea why the head is traditionally grounded. Jim's solution proves the head does not need to be grounded.

So then why ground it?

If the wiring loop is grounded, why is further frame grounding needed?
 
highdesert said:
And I have no idea why the head is traditionally grounded. Jim's solution proves the head does not need to be grounded.

So then why ground it?
Click to expand...

The plugs and points need a ground return connection back to the battery, via the frame and/or harness ground wires (the electric start 850 MkIII being the exception and needs a heavy duty direct wire), as the Isolastics make poor electrical conductors, but the connection need not be at the cylinder head, it's probably just the most covenient location to add a wire, but note the early Commandos had a ground wire close to the side stand pivot.
 
ludwig said:
Because of the isolastic system , the engine ( craddle) needs a dedicated ground , for the plugs .
In my experience , in case of an electrical problem , ground connections are among the first suspects ( suffer more from vibration ? ?)
so I like to have them where they are easily checked , not hidden .
Click to expand...


I would rather have it where it doesn't break. With points ignition it's no big deal. The ground wire breaks-the bike quits and you fix it. With electronic ignition it's a different story. If the ground breaks the bike continues to run just fine- until the ignition amplifier dies from voltage spikes from an open ground. So use both grounds to be safe. Jim
 
Can you not just do it here?
Grounding the Motor
 
dunno, I was just thinking from there to under the cradle (or on mine under the e-start) up to the battery box area somewhere
 
My guess is that the ground wire to the head was because of it's close proximity to the wiring harness.
 
pelican said:
dunno, I was just thinking from there to under the cradle (or on mine under the e-start) up to the battery box area somewhere
Click to expand...

If it is an electric start model, then don't connect any light gauge wire directly to the battery positive terminal and don't connect any other light gauge harness wire to battery positive-even though one is shown on the MkIII wiring diagram it's not advisable to fit it, because it could result in a harness fire during starter motor operation if the heavy gauge cable had developed a bad connection. Only connect the heavy gauge starter positive wire to the battery positive terminal if the starter motor is operational.
 
I use the exact point Pelican shows in his photo. Because I have a Mk3, the ground cable is substantial, 4 gauge marine cable, and it connects directly to the battery. Still in break-in mode after 14 months, so I can't vouch for its robustness, but the cable and terminal are truely massive.
 
Dave,

Ground loops are only important in rf circuits. There are no circuits of high enough frequency on a commando to cause this concern. Ground away.
 
rick in seattle said:
Dave,

Ground loops are only important in rf circuits. There are no circuits of high enough frequency on a commando to cause this concern. Ground away.
Click to expand...

Thank you.
 
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