No Start - Voltage Drop While Cranking

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bkellis1

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I picked up a non-running 81 XS650 back in January 2022, and spent the first six months working on it to get it running. Got it running by June (thanks to many of you on this forum) and had a ton of fun on it all summer long and into the fall. When it got too cold for me to ride, I parked it for the winter. That's when a similar "too cheap to pass up" bike turns up so I turn my attention to that one. I steal the battery from the XS to start playing around with the other bike. Recently had a warm day, so snagged the battery back to put into the XS. It fired up and I rode around for the afternoon and again parked it for winter to pass. Went to the garage the other day, tried to start the XS and nothing, just cranked and cranked (electric start) until I ran down the battery. Thought "that's weird", I was just on this damn thing a month ago. Threw a battery charger on it and moved on. Went back, same thing. Thought it might be the carbs, so shot some ether to it and it fired up for a brief second. Ok, guess it is the pilot jets in the carbs, even though had rebuilt them the first time around getting the bike running. No dice, still didn't start after another carb rebuild. Confirmed I had spark - yep. So then I just started going down the list: 1) fully cleaned/rebuilt the carbs again 2) adjusted the cam chain tensioner 3) adjusted the values and then went on to adjust the timing. Thought maybe the Boyer Bransden rotor might have spun in the cam since it's only held in place with the all-thread and tension from the nuts. Started making the expected adjustments (put the dot in the hole while at full advance), added timing light to see where it was hitting and cranked it over. Timing mark seemed to be jumping all around - that doesn't seem right! This reminded me of the threads I had read here about the Boyer Bransden being sensitive to voltage, so added my multi-meter to the battery leads. Voltage before hitting the e-start button: 12.x volts. Hit the starter and the volts quickly drop to 11, then 9, then 8, then 7. Pretty sure that's why it's not working properly, BUT why such a drop in voltage? Is the starter causing too much of a drag on the system? Do I have a short in my starter switch or somewhere between the switch and solenoid/starter/battery? Or is it just the battery needs to be replaced (too many charging cycles due to troubleshooting or maybe overcharging since I never checked the PMA after getting it running the first time - just rode the hell out of it over the summer)?

Here's the specs on the bike:
Boyer Bransden ignition
PMA (not sure from where)
Bike completely rewired by me based on wiring diagrams on this site and others (simple/minimal chopper wiring, not even keyed, just on/off switch to power up the bike)
New battery from first build efforts (but multiple discharges and recharges from troubleshooting this bike as well as the other piece of crap I just bought)

I did recently buy another battery for the other bike so I wouldn't have to swap them out. Tried that new battery with the same results. No start but significant drop in voltage while cranking. Maybe crappy new battery or should I be looking for a short or something else altogether? Any other information needed to help troubleshoot?
 

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I would charge the batteries let them sit a day and measure Voltage
Then install a battery and kick start measuring charging Voltage across battery

Since you have tried 2 batteries they are most likely OK unless the charger kills them.
Then we take it from there
Please provide a Schematic if Known of the wiring

Not heard much of starter shorting but a lot of Charging regulators on PMA
 
Normally, I'd say the battery is the prime suspect; but two? If you think you've properly charged the newer of the two - and it's a (the) ETX15L - and still having the issue I'd be checking and cleaning connections - grounds too. Curious; what gauge wire are the battery leads and the starter cable?
 
I’m with JPD on the connections but it’s easy enough to trace the voltage across the components Which you say is just a toggle switch but that may be losing ground as well or a loose starter cable.
 
I've never had any luck trying to kick start the bike. Maybe I had the timing too advanced - sometimes it would kickback pretty hard.

To clarify, that first image was of the first battery I used. The newer one is a cheaper battery from Amazon - screenshot attached
 

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I’ve used those Mighty Max batteries in several bikes and never had an issue. No problems with using the e-start.
 
Here's the wiring diagram I used. You'll notice the post-it note where I had to add a hot wire but I don't remember exactly where that was spliced in. This came from a couple different diagrams here and there and this was me trying to make sense of it all
 

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If I remember correctly I used 16 gauge wire for the entire thing except for the cables going to the battery and those are the normal heavy duty cables
 
Looks as there is Power on the R/R as soon the battery is connected regardless how switches are set
I have no experience on the internals of those PMA regulators
But there is a risk there.
 
I think that battery is a little light @ 12Ah, standard is 14Ah: these bikes like 220-230CCA.

16ga is fine on the normal wiring, but battery cables, engine ground & starter positive cable should ideally be 8ga min.
 
I am thinking inspection of the relay circuit push button ,and wires to Starter
 
I can't say I really understand any of it. I just cobbled together diagrams for the different systems from various sources and tried to write it down in a way that made the most sense to me to the best of my understanding. Obviously I didn't get it right the first time around, hence the post-it note to myself 🥴

I've read about connecting 2 separate batteries so you have one just running the BB ignition. I just don't know where to connect another battery into the equation. Any thoughts there?
 
bkellis1 said:
I can't say I really understand any of it. I just cobbled together diagrams for the different systems from various sources and tried to write it down in a way that made the most sense to me to the best of my understanding. Obviously I didn't get it right the first time around, hence the post-it note to myself 🥴

I've read about connecting 2 separate batteries so you have one just running the BB ignition. I just don't know where to connect another battery into the equation. Any thoughts there?
Click to expand...

Since I am not so experienced on these -- But lets try the battery charging first according to #2
Or take them to a shop or garage having them test.
This was a running bike if I understand it right So the mean demon sneaking into the garage.
Trashing it all Aeehh..hhh l

Try batteries first then we can think if some clever disconnecting Starter ?? can be done
How many fuses inside the box ?

Would help if it can be Kick started measuring Charging--- Boyer is sensitive for Voltage but with fully charged battery it can be better.
 
Last edited:
As luck would have it, when I swapped to the new battery, I put the old one on the charger overnight. It's been over 24 hours since and I just checked it and it reads 12.74 volts. Going to take it to a parts store tomorrow for a load test. I'll report the results afterwards.
 
bkellis1 said:
Auto parts store just ran a load test and confirmed the battery is good. Troubleshooting continues...
Any suggestions for next steps?
Click to expand...


How many fuses in Box ?
Again I am not really experienced on these -- I would look into
Install the battery which i charged and OK -- test se if the problem is still there.

I would look into measure currents in wires I rarely do that ..but open the starter feed before the Relay
or after
First at key on and then then when cranking note if the meter can take it

and measure the current going through

Skärmbild från 2023-03-16 00-04-02.png


I would consider to disconnect the wire feeding lights for the moment


Skärmbild från 2023-03-16 00-10-37.png



Then if nothing is found measure in those two

Skärmbild från 2023-03-16 00-12-47.png
 
Okay here's the latest...
After confirming the battery was good, I get home and thought, well I will try to kick-start it so that all of the power of the battery is going straight to the ignition. Nothing. So then I thought, well maybe it is the carbs, so I shot some ether to it and try to kick-start again. Nothing. Frustrated, I decide to take out the plugs to make sure I'm still getting a spark and again nothing, no spark. Well that's crap, I had a spark earlier, I wonder what's going on. I disconnect the two leads that you can touch together to force a spark from the Boyer Bransden, and nothing at first. But I could hear a clicking sound, so I continued to do it, and then at least one of the plugs started to spark, but not the other. I ended my testing there and wanted to bring it back to the forum here. Does that mean I have a bad coil or is the ignition box going out?
 

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