Random stalling, trouble starting when warm

peterg

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I can start my bike with one or two kicks with the choke on when cold. It stalls randomly during warm up and when idling at a stop and I have trouble starting it when warm.

Today it stalled when warming up. It wouldn’t start again so I pulled a plug to see if there was spark. I used the push button without choke or throttle and she was on the verge of starting with one cylinder. (There was spark at the pulled plug). Replaced the pulled plug and it took many kicks and breaks to get it going again. Many kicks did not bring any sign of ignition.

Top end was rebuilt over the winter. Carbs are VM34s and I cleaned them at the start of the season. Float heights are at the middle of the range.

Any idea of what is going on?
 
Air, fuel, spark. Assuming you have air, was the plug you pulled wet or dry? Wet, spark problem, dry, fuel problem. I.E. more info? This is not a tongue in cheek response, more a request for more information.
 
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In pondering your issue, I needed to know what ignition you were running (searched threads) - also found out you're one smart fellow. So, issues starting and issues when warm: I'm going to jump to a wild-ass guess and suggest you check the PAMCO e-advance. I also ask what alternator and regulator set-up you have? (if my guesses are to become less wild) lol.
 
I would start with checking your timing with a strobe. If your timing is correct then time to look for carb or mechanical issues.

Has it been hard to start all along or is it a new issue ?
 
Thanks for the replies. Here is some more info.

The bike has never started while cold better than it is now.

Stalling and not starting while warm is a new issue this year.

After running the plugs are clean at the electrodes but a bit sooty on the rim. They are always a bit sooty after choke starting.

I did a complete tune this year - cam chain adjuster, valve gaps, timing. I will check again.

Over the years I must have removed the plugs hundreds of times trying to tune the carbs. At one point this year the bike was running on one cylinder. Turned out there was no cap to plug connection. I used contact cleaner and compressed air on the caps.

I have new caps on hand.

PMA charging to 14+ volts.

Last year most of the pamco wire connections snapped, resulting in 3 tows. All connectors were replaced.
 
What coils?
This one from XS650 direct. It came with the pamco/pma kit I installed when I built the bike in 2016/17. Running with only one spark working may have something to do with the issues.

I went for a city ride today for about 25 minutes - barely got into third gear. Started on the third kick. First two with the choke and the third without. Low 20s C/low 70’s F. Got home turned it off. Started with one or 2 seconds on the electric start.

Gremlins?

A83ABFB8-A0F2-4D4D-A2B4-1D5AD2F88542.png
2DB70E1F-476C-47EC-B930-2551C1CAD223.png
 
"No connection at plug cap" (unusual), cleaning.....yes, you know that could have compromised the coil. The XS Charge (not PAMCO) e-advance ignition is also a prime suspect ("snapped connectors" unusual). You refer to kick-starting mainly, but also electric start use (unusual). What battery type and/or capacitor are you running?

The whole damn thing needs checked "stem to stern".

Also, there's this recent thread, perhaps start at post#143 (it gets better toward the end)
https://www.xs650.com/threads/81-xs650-running-but-have-issues.61511/page-8
 
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Thanks jpdevol.

I’m worried the coil may be damaged from running the bike just for a minute or two with only one plug connected. It’s odd that the bike does start and runs the best since I’ve had it (due mainly to the top end rebuild I’m guessing) except on the odd occasion.

The battery is new this year Shorai lithium.

The ignition system is a real pamco. I’m not surprised that the wires snapped at the connectors, since they are only 22 or 24 AWG, after 5 seasons of riding on rough Toronto roads.

My plan is to check continuity on the coil when I remove the resistor caps to replace them with new non-resistor caps. I have a pile of resistor plugs to go with the new caps.
 
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In the past there has been a lot of trouble with the attachment probes on those coils. They come loose and have been known to fall out completely...........check them
 
I noticed today that the voltage reading at idle is bouncing around a bit but generally under 12 volts and maybe dropping below 11 at times. With the motor off and the head light on around 12 volts and with the head light off it’s just under 13 volts. When running over idle it’s just over 14 volts.

I think that low voltage at idle could be the reason for stalling (?). I haven’t noticed this low voltage ever before and I’m not sure what would cause this.

To recap the bike is equipped with a kit from XS650 Direct (mikes Canadian branch at the time of purchase) containing a pma, reg/rec and a pamco ignition with auto advance, a Motogadget m-unit, and a Shorai lithium battery. These components have been on the bike since I built it in 2016/17, except for a replacement battery installed this year. Here is a link to the mikes pma kit currently offered. I notice it states “not compatible with lithium products”. I can’t say if the note was there or not when I bought the kit years ago. Up until now I have not had electrical issues.

https://www.mikesxs.net/yamaha-xs650-xscharge-permanent-magnet-alternator-kit-pma-200-watt.html


Any ideas what would cause the low voltage?
 
I noticed today that the voltage reading at idle is bouncing around a bit but generally under 12 volts and maybe dropping below 11 at times. With the motor off and the head light on around 12 volts and with the head light off it’s just under 13 volts. When running over idle it’s just over 14 volts.

I think that low voltage at idle could be the reason for stalling (?). I haven’t noticed this low voltage ever before and I’m not sure what would cause this.

Any ideas what would cause the low voltage?
I have no personal experience with the PAMCO or the XS charge. The voltage drop (12 key-on to <11 @ idle) indicates excess draw from ignition or weak (perhaps) PMA. Current idle rpm? Good ground(s)?

Hope someone with specs for those components for chime in.....
 
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I’ve set the idle a little higher than spec. It’s around 12.5 or 13k. Pma seems to be charging when above idle. Grounds are good as far as I know. There are just 2. Direct from battery/m-unit and one from the loom to the frame at the coil mount.

wiring diagram - black brat - updated 2022 01 23.svg.png
 
Your idle voltage sound normal and shouldn't be the cause for stalling. At idle, I see high 11's (lights on), or high 12's (lights off). The lights are a big draw at idle, gobbling up a volt or so. At speed, I notice little, if any, change in voltage output on my voltmeter when switching the lights on and off.
 
Please do not take this wrong. I am relatively new here and have been sorting a new to me bike. Some minor charging issues, some needed updates and carb jetting that was WAY off. As I got the carbs pretty good I started feeling proud but still had an erratic idle. I discovered the sync was the problem and now my idle is very steady when warm. Is it possible your sync has drifted? This represented maybe 1/2 turn out of sync.
20220708_125318.jpg
This represents smooth even idle
20220710_120119.jpg
 
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Your idle voltage sound normal and shouldn't be the cause for stalling. At idle, I see high 11's (lights on), or high 12's (lights off). The lights are a big draw at idle, gobbling up a volt or so. At speed, I notice little, if any, change in voltage output on my voltmeter when switching the lights on and off.
Perhaps my reading of OP's description is wrong, but I'm understanding at least a full volt drop from just ignition at idle with a 200W PMA and PAMCO.?

Is there a dedicated ground to engine?
 
5twins. Thanks for the reassurance. I don’t think there is a difference at speed with the lights on or off but that’s just an assumption since I get 14+ volts with the lights on. I can’t turn off my lights once they are on without turning the key off. With the m-unit they (head and tail lights) turn on when pressing the electric start. They don’t come on automatically when kickstarting but a flick of the beam selector turns them on once running. I wired up a warning light/relay to indicate when my lights aren’t on to remind me to turn them on after starting with the kicker.

TeamWicked. Thanks for the input. I haven’t used my manometer yet this year but will do so. I’m constantly checking the carbs’ sync with a a hex wrench (best thing in my tool kit to use) and hands-feeling-exhaust method.

Jpdevol. With switch and lights on but motor not running I have 12+ volts. When running and lights on I have 11ish volts. So yes, running the engine causes a voltage drop. The main ground is from the battery to one of the electric start mounting bolts at the engine. I will double check the connection. I rebuilt the motor over the winter but had my mechanic install it.
 
Could be carb or other issue, however, the issue "when warm" and the curious voltage readings would have me focusing on electrical, and specifically ignition, issues to conclusion before moving on. See, you're running a PMA - no field coil to power - so that part of running engine should normally draw less wattage @ idle. The output on the stator should be ~15VAC @ idle (between output wires). That brings you back to coils, plug caps and PAMCO: are there issues causing too much draw that gets worse when warm (increasing resistance)?
 
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I got around to testing the existing coil.

The readings are:
Primary 5.5 ohms
Secondary 26.4 K ohms with resistor caps. Approx 16k ohms without

No connectivity between primary/secondary/ground.

My Haynes manual states resistances should be:
P 2.5 +/- 10%
S 13k +/- 20%

Pamco instructions state:
P 2.5 to 4.5
S 15 to 20k

The numbers tell me that my primary resistance is too high.

I have 2 coils on hand.

An XS650 coil
P 4.5
S 13.2k

Unknown bike coil
P 3.5
S 15k
This seems to be the best bet although I’ll have to make a bracket since the connection holes are too close together for the frame.

I also noted that will starting the bike today that, as before, with no lights and not running the battery reads around 13.2 volts.
After each kick the voltage randomly changes. Sometimes it was reading 13.2. After other kicks it was 12.

Any suggestions on the coil reading and the wonky voltages after each kick?
 
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