Blowing 20 amp main fuse

Shipper

Shipper

XS650 Addict
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Just finished installing new points, removed and replace timing/advance cam for polishing and lube, static timed bike ('75 650xs) - now starts and runs better than ever - for five to twenty minutes before blowing 20 amp main fuse. Removed tank and covers searching for that illusive bare wire to no avail. Any suggestions before I rip the whole harness apart?

Thanks,
 
As I understand it the bike ran fine before service and nothing else is done.
No other symptoms ... misfiring ? ?
I am not sure but there should be a Ignition ( 10 A ) fuse and if I understand it correctly
it does not blow.
But since you mention the new Point .I would start there
To much lubricant ??
All washers there in place. ??
Defect Point ??
Is it clean under the points cover. ?
A blob of grease short circuit one point when heat comes on after a short ride. ?

I Would also check the charging Voltage across the battery .. Since I Once had a faulty regulator
That gave to high Voltage Causing the electronic ignition to malfunction.
 
Jan_P said:
As I understand it the bike ran fine before service and nothing else is done.
No other symptoms ... misfiring ? ?
I am not sure but there should be a Ignition ( 10 A ) fuse and if I understand it correctly
it does not blow.
But since you mention the new Point .I would start there
To much lubricant ??
All washers there in place. ??
Defect Point ??
Is it clean under the points cover. ?
A blob of grease short circuit one point when heat comes on after a short ride. ?

I Would also check the charging Voltage across the battery .. Since I Once had a faulty regulator
That gave to high Voltage Causing the electronic ignition to malfunction.
Click to expand...


Was running well prior to new points with exception of breaking down at top end. Also replaced the condensers. That’s why I pulled the tank again looking for pinched wires.
 
If you pulled the tank, there's a good possibility you disturbed the harness going into the headlight bucket. Look see if there's a cracked/missing grommet in one of the holes and a wire chaffing. Is the 20A your only fuse or do you have a separate ignition fuse?
 
Jim said:
If you pulled the tank, there's a good possibility you disturbed the harness going into the headlight bucket. Look see if there's a cracked/missing grommet in one of the holes and a wire chaffing. Is the 20A your only fuse or do you have a separate ignition fuse?
Click to expand...


20 amp only. Been in the headlight bucket once already searching for the problem and found nothing. Likely start there for a second look tomorrow morning. Thanks Jim.
 
I just think these old dry rotted harnesses should be replaced. They're not safe. Starters draw a lot of amps by usually a fumey, leaky, flooded carb. Replace fuse box and all. Plastics, rubber, insulation just goes bad over time. I understand wanting something original too. this is expensive and labor intensive. If there's tape around the harness, heat shrink, you're still not gauranteed it's ok. Put some current thru that old wiring.... I have a 2010 Triumph with wiring issues. Not old just not the best engineered. I sound over opinionated but hey, I've had a fire or two.
 
Last edited:
Shipper said:
20 amp only. Been in the headlight bucket once already searching for the problem and found nothing. Likely start there for a second look tomorrow morning. Thanks Jim.
Click to expand...

Could maybe/hopefully have found it! Rear power wire from condenser bare spot and touching barely the casing. Will know shortly.
 

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JRay77 said:
I just think these old dry rotted harnesses should be replaced. They're not safe. Starters draw a lot of amps by usually a fumey, leaky, flooded carb. Replace fuse box and all. Plastics, rubber, insulation just goes bad over time. I understand wanting something original too. this is expensive and labor intensive. If there's tape around the harness, heat shrink, you're still not gauranteed it's ok. Put some current thru that old wiring.... I have a 2010 Triumph with wiring issues. Not old just not the best engineered. I sound over opinionated but hey, I've had a fire or two.
Click to expand...

Hear ya JRay. My history is with British. Lucas electrics are a nightmare.
 
Hate to point this out, but that's a ground wire. It's supposed to be shorted. Sorry.
 
Shipper said:
Was running well prior to new points with exception of breaking down at top end. Also replaced the condensers. That’s why I pulled the tank again looking for pinched wires.
Click to expand...

How about putting back the old Condensers ?? As a test

I found a schematic for a 75 Circuit
Points go to ground but Condensers also do that . And should not be a difficult switch
Not in comparison with finding it in the wiring elsewhere with only one fuse.
 
Dih
Jan_P said:
How about putting back the old Condensers ?? As a test

I found a schematic for a 75 Circuit
Points go to ground but Condensers also do that . And should not be a difficult switch
Not in comparison with finding it in the wiring elsewhere with only one fuse.
Click to expand...


New condenser going in tomorrow. Thanks.
 
Zoom out a bit and take another pic. The condenser should be case grounded.... no ground wire. The two wires out the ends tie into the points.

Untitled.png
 
The case/bracket that holds the condensers is the ground. There is no ground wires attached to the condenser pack. The 2 wires coming out of it tie the coil and points together.... 1 for each side. If those 2 wires are attached to ground, the condensers aren't doing anything.

Untitledbb.png
 
Last edited:
Shipper said:
Thanks Jim. Good info - makes perfect sense but different than how mine is wired and run for 2 years now. Working on it.

Thanks again
Click to expand...

PS, want you to know what I started with and where I am today,
 

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