Strange stalling issue - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 42 (permalink) Old 07-18-2019, 06:46 PM Thread Starter
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Strange stalling issue

Evening all,

The Bonnie has developed a new issue; occasionally when I pull up at a junction, she stalls. Once kickstarted again (which may take a few tries) she will tickover perfectly well and off we go. She might be ok at the next junction but she might not, it's a lottery...

Now, this seems to coincide with the point when I replaced all the control cables, as I didn't have this feature before (at least when she was warmed up). To do this I removed the flat bar that braces the carbs together, removed the fuel banjo on one carb and loosened the clamps on the large rubber pipes that connect carbs to head. This allowed me to rotate the carbs outwards so that I could remove the carb tops, without removing the carbs themselves. I replaced the throttle and choke cables, put everything back together, then carefully set the carb-top cable adjustments so the slides were perfectly in sync and refitted the air filters and air box. I also adjusted the choke cables so both had exactly the same small amount of play to ensure that when the choke was off, the plungers would seal to the enrichment circuit (even with the handle bars on full lock) and that they would both move at the same time with the choke lever. So, all should be as it was before, but I now have the stalling issue.

This is almost definitely fuelling. Apart from the fact that everything on the ignition side is new/high-quality stuff, she splutters when she stalls (as though she is running out of fuel) and occasionally I can catch the stall by feathering the throttle. I have tweaked the idle speed a little higher (around 1100rpm) and adjusted the mixture screws to 1 full turn out from the point where screwing them in starts to drop the idle (which is around 2.25 turns out from fully in). This seems to have reduced the problem a little but she still splutters a little at some junctions and a little less occasionally than before, still stalls.

Any ideas please? What could have changed?
Ian
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post #2 of 42 (permalink) Old 07-18-2019, 07:30 PM
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First, Iíll tell you I donít believe in coincidence , so something you just did has changed the hot idle . Second, Iíll tell you they still happen whether I believe in them or not. You sound as if youíre pretty meticulous, but anyone can miss something. Make sure your carbs are level, and spray starting fluid around the manifolds while idling to check for an air leak. Make sure the carbs are properly seated in the manifolds and that you didnít overtighten, creating an air leak. I would remove the mixture screws and spray some carb cleaner in each, just to be sure something isnít plugging the passage. I would run some carb cleaner through the fuel system. Are you sure you have adequate fuel flow and you didnít kink a line when you moved the carbs around ? How old are your spark plugs ? Might they be due for a cleaning or change ? Make sure the spark plug wires are ok and plugged in well on the caps and coils. If you have a spark checking gadget, use it. If youíre not getting consistent fire on both sides, find out why. Do you keep the bike on a maintenance charger ? They dont generate a lot of juice at low rpm and a charged battery will help them run in stop and go traffic. I run my idle around 1200 rpm.
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post #3 of 42 (permalink) Old 07-18-2019, 07:59 PM
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Iíve had problems stalling in traffic, but when the temperature is really hot and so is the engine. I have fairly worn out Amalís, so I know thats part of it. When I had the problem I was parking outside and getting a little moisture in the fuel that collected in the float bowls periodically. Iíve loosened up my valve clearances a bit, and installed a Podtronics regulator with the built in capacitor. Weíll see.
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post #4 of 42 (permalink) Old 07-20-2019, 06:01 AM Thread Starter
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Thanks for the reply. Checked all that out last night and there is nothing obvious but left the battery charging. The strange thing is this only happens when I come to a halt. I can pull the clutch in whilst riding and she settles to a stable idle as I freewheel along but pull up at a junction and she stalls.
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post #5 of 42 (permalink) Old 07-20-2019, 08:07 AM
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Quote:
Originally Posted by Boggie View Post
Thanks for the reply. Checked all that out last night and there is nothing obvious but left the battery charging. The strange thing is this only happens when I come to a halt. I can pull the clutch in whilst riding and she settles to a stable idle as I freewheel along but pull up at a junction and she stalls.
Hi Boggie
It seems to me that the only difference between pulling the clutch in while riding and coming to a halt, is the brake light is on during coming to a halt.
I am wondering if the battery is low, or you already have reduced voltage at the electronic ignition through poor connections, that putting the brake light on drops the voltage further.
Low voltage on an electronic ignition tends to advance the spark, maybe to the point that you are losing power at tickover.

You should have a 3 phase alternator fitted as standard equipment on a 79 T140E.
If you lose one connection or diode in the rectifier you are left with low a single phase output. Enough to run the bike without lights, but not enough to keep the battery charged.

I think I would be tempted to confirm the voltage at the electronic ignition supply point, with and without brake light on.

There is a small chance that this is the problem, but it is easily testable to eliminate it from your enquires.

Regards
Peg.

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post #6 of 42 (permalink) Old 07-20-2019, 09:26 AM
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You know, this occurred to me too. I was thinking seriously of installing an LED taillight bulb . Obviously if you have an electrical issue that should be addressed first. The lower draw may be enough to keep the bike from stalling if insufficient current is the problem. $20 but if it stopped the bike from stalling at lights it would be worth it. Iím putting the Podtronics on with the hopes of charging my battery better. If it does stall Iím hoping the capacitor will help it start better when Iím sitting there in 6 lanes of traffic !
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post #7 of 42 (permalink) Old 07-20-2019, 07:30 PM Thread Starter
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Oooh! You might ave nailed it there and charging was something I was suspicious of. I was thinking of replacing the charging system, ideally with the best available / highest output option in the future. It is on the list of potential areas of improvement that I would inevitably pick the collective Rat forum brains for candidates. As a cause of my recent stalling issues this potential suspect makes a lot of sense for the following reasons:

I always ride with my headlight on. It gives the Volvo divers something to aim for.
On my recent ride with headlight on, the indicator lights (neutral, oil etc) were rather hard to see. I had initially put that down to bright sunlight.
I generally brake at junctions, so there will be additional 21W of demand upon the battery.
I hooked up my "intelligent" charger last night and was expecting to come down to a fully charged battery in the morning. However, whilst admittedly in "recondition Mode" (which adds an extra stage to the process) it took until early this evening to complete the cycle, i.e.20hours. So, this seems to indicate that the battery was rather low...

I will take it for a ride tomorrow to see if the fully charged battery has resolved the issue and measure battery voltage Off, running and running with lights. Will report back, thanks!
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post #8 of 42 (permalink) Old 07-20-2019, 10:42 PM
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You can get approx. 300km highway/country riding [I've done 340km but it was missing by the time I stopped] with a healthy/good battery and no charge if you don't use your headlights indicators or brake light. It was illegal, but I disconnected the brake light switch so I could use my brakes....but I was in the country and careful not to brake suddenly with other vehicles behind me.

So I'm thinking that your battery is either not getting a charge or is 'past its use by date'.

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post #9 of 42 (permalink) Old 07-21-2019, 03:41 AM
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Hi Ian,

Quote:
Originally Posted by Boggie View Post
I was thinking of replacing the charging system, ideally with the best available / highest output option
I hooked up my "intelligent" charger last night and was expecting to come down to a fully charged battery in the morning. However, whilst admittedly in "recondition Mode" (which adds an extra stage to the process) it took until early this evening to complete the cycle, i.e.20hours. So, this seems to indicate that the battery was rather low...
Mmmm ... ime, that's more-likely the battery turning up its toes, less-likely a charging system problem. Do you have the kit to load-test it or do you remember the quick-'n'-dirty 'load test' from an earlier thread?

Your bike originally had a 3-phase stator as standard (individual wires out of the black insulation out of the primary are White/Green, Green/Yellow and Green/Black), albeit the 'low-output' version (10.5A/120W @ 5,000 rpm, 85% @ 2,400 rpm), 3-phase square plate rectifier and either a single Zener across the battery or a strip of three, one connected to each alternator phase.

When Lucas developed the 3-phase alternators, afaict it was primarily to address the increase in requirements and desire to ride lights-on all the time even at low engine rpm since the succeeded RM21 and RM23 had been developed. So there wasn't any increase in the rated Amps @ 5,000 rpm over the previous single-phase, just an increase in percentage of rated at lower rpm. I'm not saying the high-output 3-phase isn't a nice-to-have, just be careful you aren't treating a symptom of a fault or PO change elsewhere?

It's possible the rotor has lost enough magnetism if the PO left it out of the stator or keepers for a long time while he did the work on the engine. I'm guessing you know how to check for DC Volts rising with engine rpm and stator Amps with either an AC Ammeter or a load resistor and AC Voltmeter? If not, I'll be pleased to run through the processes.

Digressing slightly, absent failing components, the only substantial improvement available is a high-output (14.5A @ 5,000 rpm) 3-phase stator; if you bike has a single Zener, you'd also need a reg./rec because the 'three Zeners' strip is NLA.

Quote:
Originally Posted by Boggie View Post
I always ride with my headlight on.
On my recent ride with headlight on, the indicator lights (neutral, oil etc) were rather hard to see.
I generally brake at junctions, so there will be additional 21W of demand upon the battery.
As I say, when Lucas developed the 3-phase alternators, it was primarily to address the increase in requirements and desire to ride lights-on all the time even at low engine rpm. So your bike shouldn't have a problem, bar a fault (assuming you aren't chugging it around like a Hardly? ).

By the time the Co-op built your bike, thankfully they and Lucas had finally given up on the execrable BPF bulb and lens/reflector; your bike originally had a 45/40 P45t bulb and decent lens/reflector - the bulb hasn't been changed for either a 60/60 non-qh or a 60/55 qh?

Because the (original) lens/reflector is so good at focussing the headlamp light, fwiw when I dispatched and commuted on Japanese bikes that used the same bulb, I fitted them with a 20W quartz-halogen pilot bulb and used that around town - lower current draw and a wider spread of light; other road users are more likely to see it before they're directly in front of the bike? That said, those q-h bulbs aren't so easy to get these days, and others have posted on forums that they don't last too well on 'big' twins; if the headlamp bulb is correct, maybe consider the suggestion that @rambo has posted a few times, of a 10W or 20W Eagle Eye LED in place of the pilot bulb and holder?

Hth.

Regards,
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Stuart

Last edited by StuartMac; 07-21-2019 at 08:11 AM.
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post #10 of 42 (permalink) Old 07-22-2019, 05:14 PM Thread Starter
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Thanks All,

After a full 24h charge, I took the Bonnie for a ride with the headlight off. No stalling issues at all! Now I just need to find time to see if this is the battery or the alternator. I have all the test kit I need but have not had the day-time to look.I can't run the bike in the evenings as with 1.5" headers and straight-through Norton pipes it is rather loud and I don't generally get back from work until kids bedtime.

So I hope to get a chance this weekend to get her up to temperature then measure the charge voltage at various RPM and load-test the battery. The battery is fairly new (late last year) and according to my "intelligent charger" the battery is good but I have a proper battery analyser / load tester that gives comprehensive reports on battery performance and life expectancy etc so I will get back to you.

I would potentially still be interested in fitting a higher-output alternator or perhaps LED main/dip bulb if there is one suitable for these old girls...

Ian
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