Blowing 20 amp main fuse

Shipper said:
Don’t know if you got this but battery charging at 13.58v
Click to expand...

Got the message charging voltage looks right if it is with lights on and a little higher rev-
The gentlemen who knows this year model are coming with suggestions
To sum it up
Ignition appears --- emphasizing appears to be right new parts and the same coils.
Charging are giving the right voltage. --.appears emphasizing appears to be right
Lower rpm makes the fuse hold at little longer.

I shall look at the schematic see if I can figure something out. Later tonight.
But more fuses would be way forward I have 4 on my 1980
Ignition / Signal / Headlights / Main.

Depending on the Circuit there can be a Possibility to draw own wires from Battery to function and from function to minus on battery.
Bypassing the harness entirely .In a stage of fault finding.

I am still at the charging circuit and it would be there I inserted the first extra fuse.

By the way a stupid question of Course since i Always had Crap Bikes always kick starting by the Schematic there are a Starter motor with relays and stuff.
That starter motor has a direct line from battery. --- Is it connected and Used and not have any strange behavior. Working as intended and starting the bike
Which would be a first. I ever I heard of that.
?? Disconnect and Kick start ?
 
Thanks again Jan for sticking with this, its really got me baffled.
1. your assessment of the situation is accurate with a couple of additions. This all started after I replaced the points and pulled and cleaned the timing/advance cam.
2. The electric start has never run better but it kick starts just as well.
3. The charge rate I gave you was at idle. I will turn on all lights and rev for a check and get back to you.
4. Was breaking down at top end prior to points replacement and new static time but it runs and starts better than ever now - until the main fuse blows of course. (5 to 20 minutes of running).
 
It appears you're not charging? Rate should change and be higher when revved. Although I'm not sure why no charging output would blow fuses.

If you have the original mechanical voltage regulator, it can be adjusted. I rode my '78 for the first few years I had it with a charging voltage lower than optimal (mid 13's revved). I had no battery issues or fuse blowing though. When I finally discovered I could adjust the regulator, I did so, turning it up so I got low 14's. But around that time I also installed a means to monitor voltage on the bike. That's when I noticed the mechanical regulator's output was very erratic. It would sometimes drop low even while I was cruising down the road at 3500 to 4K. Maybe yours is doing the opposite? Spiking too high from time to time? It might be time to consider the VR115 swap. I did it and now get nice stable charging in the low 14's, no bouncing high and low like before.

But if you are getting no charging output, you've got other things to check, namely your rotor. But you should probably also check your rectifier. That open air original can get all crusted up hanging under the battery box like it does.
 
Shipper said:
Thanks again Jan for sticking with this, its really got me baffled.
1. your assessment of the situation is accurate with a couple of additions. This all started after I replaced the points and pulled and cleaned the timing/advance cam.
2. The electric start has never run better but it kick starts just as well.
3. The charge rate I gave you was at idle. I will turn on all lights and rev for a check and get back to you.
4. Was breaking down at top end prior to points replacement and new static time but it runs and starts better than ever now - until the main fuse blows of course. (5 to 20 minutes of running).
Click to expand...


I would also expect changes in voltage when revving unless it is already an electronic regulator

Are we ready for fuses. ?
So if we shall go with the flow and Jim
At the Circuit --> https://thexscafedotcom.files.wordpress.com/2012/01/75-xs650b-wiring-circuit-diagram-2.jpg

Going into the Coils are a Hatched line red and white -- one to each coil as 12 V .Someone will protest surely if wrong
But one 10 A Fuse on each of those 2 wires Into the Coils and we can discard the ignition if the 20 A fuse burns and not any of the 2 pcs -- 10 A .

But given the no change in Charging Voltage i am still at the Charging Circuit.
Ill look into the Schematic later and get back unless someone else does it before me where that fuse goes.

Slip Ring resistance ?
 
5twins said:
It appears you're not charging? Rate should change and be higher when revved. Although I'm not sure why no charging output would blow fuses.

If you have the original mechanical voltage regulator, it can be adjusted. I rode my '78 for the first few years I had it with a charging voltage lower than optimal (mid 13's revved). I had no battery issues or fuse blowing though. When I finally discovered I could adjust the regulator, I did so, turning it up so I got low 14's. But around that time I also installed a means to monitor voltage on the bike. That's when I noticed the mechanical regulator's output was very erratic. It would sometimes drop low even while I was cruising down the road at 3500 to 4K. Maybe yours is doing the opposite? Spiking too high from time to time? It might be time to consider the VR115 swap. I did it and now get nice stable charging in the low 14's, no bouncing high and low like before.

But if you are getting no charging output, you've got other things to check, namely your rotor. But you should probably also check your rectifier. That open air original can get all crusted up hanging under the battery box like it does.
Click to expand...


Well this is a bit different. Charges at 13.10 to 13.58 at idle and as high as 13.98 at rev but blew 2 fuses at high rev!! Thoughts?

PS I changed out the old rectifier with a Mike's replacement a couple of years back but did notice its getting pretty greasy.
 
Shipper said:
Sorry for the miss-read on voltage but it is somewhat irregular.
Click to expand...

I am all set to do Jim's coil check this afternoon. Good a place as any to start unless the blow at high revs triggers something with you guys. Three of four blown fuses on the road were also at high load.
 
I assume you mean you replaced the original separate rectifier AND regulator with the combined unit from Mike's. I would never do that. They're very expensive and I have no faith in their long term durability. Maybe yours has gone bad. If you still have the original components laying around, I think I'd put them back on and see if that solves the fuse blowing issue.
 
Shipper said:
Well this is a bit different. Charges at 13.10 to 13.58 at idle and as high as 13.98 at rev but blew 2 fuses at high rev!! Thoughts?

PS I changed out the old rectifier with a Mike's replacement a couple of years back but did notice its getting pretty greasy.
Click to expand...

Rectifier and grease does not sound right.
Could be interesting to know the current.
If you are able to connect the ampere meter in series with the fuse.
Measure at idle ..lights off take a reading
Switch lights on new reading.
Pull the brakes Se if something spikes.
And lastly rev Se what happens if it increases. Slowly or suddenly spikes.
The voltage per se is right but it is possible that it overheats and at some point gives to much
High revs is also more vibrations. Moving a loose wire
 
5twins said:
I assume you mean you replaced the original separate rectifier AND regulator with the combined unit from Mike's. I would never do that. They're very expensive and I have no faith in their long term durability. Maybe yours has gone bad. If you still have the original components laying around, I think I'd put them back on and see if that solves the fuse blowing issue.
Click to expand...

You assume correctly. Sorry for confusion. The bike ran great up until earlier this year when I started breaking down at high revs.

I believe I have the originals but like stated earlier, they’re pretty crusty.
Jan_P said:
After looking at the schematic the fuse for the charging circuit
Now you don't have a stock charging unit so please take that into consideration
But at the Schematic.
---> https://thexscafedotcom.wordpress.com/2012/01/12/xs650-75-xs-b-76-xs-c-wiring-diagram/
Into the regulator goes 3 wires.
Black Earth -
Green that goes to the rotor winding.
Brown that is Power IN

I would put the 10 amp fuse on the Brown IN
Click to expand...

OK, I will do so and let you know. Thank you. Additionally, I removed the regulator/rectifier and cleaned the dirt and oil off and replaced. Ran the bike at idle and got 13.48 +/- but when I reved to 3500 got 13.85 +/- but when I switched the headlight on - blown main fuse. So, your advice fusing the regulator may show results.
 
So, 10 amp fuse on left side regulator, brown "in" wire. Bike starts, revs well, put headlight on and 20amp main blows.
 

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Switch it to hi beam before you turn it on and see if it still blows.
 
Yes Sir this is progress
As I understand it you have a fuse on the regulator brown
How about the ignition Coils ?
But you can now reproduce the fault
GGary had a theory of rubber grommets worth inspecting.

What about the road trips ..was the lights on or off
If on try one with lights off.
Low and High rev.

A natural thing to do is to open up the connector for the lights.
On the handlebar for inspection
Maybe do some connection outside that connector.

I shall look at the schematic ..another 10 A fuse on the Lights Circuit
can be the next step.
Might not be directly i have time but I will do it.

It can be the lights circuit but we are not out of the Woods yet
The lights circuit can be fine but the sum of Current use gets to high when another
consumer is switched on.
 
Headlight power comes from the iggy switch (red/yellow) and goes into the headlight on/off sw.
Comes out of the on/off sw. on a blue wire going to the instrument lights, the park position on the iggy sw. and back to the tail light.
Another blue-green wire comes out of the on/off sw. That goes to the hi/low sw. Somewhere that power is shorting to gnd.
Start with the easy stuff... disconnect the tail light?
d 75_76_XS650 B&C Wiring and Key Updated 3a.jpg
 

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