When I went to startup my bike today, I noticed sparks shooting out from the right side of the seat. I removed the seat and see that the sparks are coming from where the negative battery cable is grounded to the frame. The sparks occur when I start the bike (bike does start). The ground was slightly loose, so I replaced the ground screw (1/4-20x1 self tapping with washer) and tightened it back down. Connections did not look corroded. I still see sparks when hitting the start button.
Bike is a '93 Fatboy with 96,000+ miles and I've never replaced the battery cables. I did install a new battery this year.
Can someone please explain what causes the sparking?
Also, if anyone has any ideas on what to check/replace to fix this.
Maybe I just need to run a wire brush on the connectors and frame connection area to really clean this up?
TIA

 

Your cable is not grounded correctly, these are usually grounded to a big fat bolt so you might want to make a decent ground terminal.

 

You have a bad connection. Remove and clean all paint/rust from the connection. I wouldn't think that a connection with a self tapping screw is your main ground connection.

 

Try using a star lock washer as well. It will help in the connection....

 

What they all said. And remember that the ground is just as important as the hot.

 

"(1/4-20x1 self tapping with washer"

This part don't make sense to me
Should be a threaded bolt I'd think

WP

 

ALL OF THE ABOVE!
Something ain't right there.

 

Damn that can be a little unsettling, see sparks shoot out from under the seat.

 

Maybe I installed the parts in the wrong order. See attached picture.
Is the order of the parts:
screw (#2, which is HD part #939, self tapping screw)
clamp (#26)
negative battery cable
star lock washer (#18, HD part number: external tooth 1/4" lockwasher)
then into frame?

 

Any chance of you getting a look at a similar bike to compare. Yea that maybe a little tuff to do but the idea of using the bolt you describe to secure a ground that important is just to much of a reach. If it came that way OEM something needs to be Fixed.

imho WP