Stall at idle

[Blurredman]

Hi guys,

Had this problem a few years so tearing what little hair I have left out..


At idle, waiting at traffic lights, my etz250 just straight up stalls. Over the years I've changed the points and condensor (and i've tried two types of electronic ignition), i've changed the coil. The bike is charging nicely and the battery is pretty decent with overnight standing voltage of 12.5v. Of course ht lead and spark plug has also been changed in this time.


The bike behaves perfectly well with no mis-fires or stutters when actually riding. Idle is set to 1300 and is stable and doesn't faulter. But on occasion when at traffic lights etc the engine will just stop without any warning or spluttering. Ignition lights stay on.

I have relayed two new wires to the generator, one from the capacitor to to the coil negative, and the regulator charge signal wire. I do intend one of my next steps to be to replace the three black phase wires. But.. I'm a bit lost now- please can anyone input?

[Puffs]

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[Blurredman]

Yes, of course it can still be a poor contact. I have already replaced the fuse box and checked continuity there when manipulating the pins.

The battery was only a few weeks ago used constantly with my 251 which does not have stall issues. More over, I've tried two batteries. Of which the one currently on the bike isn't a problem on my 251.

On this occasion yes both the left indicator and headlamps were lit.

I can't seem to re-create the problem when I am at home/work. I have been able to sit with a bike running with full load on various directions for a timed 10 minutes without a problem.


Do we definately think it is an electrical fault?

[Puffs]

No I don't, not necessarily. Swap carbs (or cheapo chinco)?

[Blurredman]

That's a good idea, and i've already been talking to someone who says about slide wear. It could be a possibility that wear is letting in too much air at idle, but I actually have the carb set 1 notch richer on the main jet needle anyway.

But swapping with another carb (from my other bike) is a possible tree to go down.

[nice2day]

Hi Blurredman. What you have to remember is that the red charge lamp does not show if the coil is getting any power or not, so the coil supply might have failed but the red light still glows. You need to have an easy reference to see if the power is getting to the coil when the engine stops. If you are intent to find the fault perhaps you could wire an LED from the coils LIVE side and to ground ...You will need a 500 Ohm resistor in series with the LED which must be connected with the correct polarity...short leg=cathode to negative (earth) . If the LED is out when the engine stops you can be certain that the connection from the switch has failed, this is likely to be the switch contact or similar..
Note do not use the earth side of the coil as this goes to the contact breaker and will be open when the points are also open.
If you don't have an LED you could always use a small wattage filament bulb of course

Les

[Puffs]

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[nice2day]

Hi Puffs...The coil supply light only needs to be there to act as a short term fault detector. If blurredman can look down and see the light as soon as the engine stops in traffic, he can know instantly whether the coil is still receiving power or not.

Of course there might be a fault WITHIN the coil but I have a way to monitor this in real-time too should we need to.... or simply do a substitution.

Whatever the outcome, the tell tale lamp can be removed afterwards.

PS: regarding the illumination flicker or not...No... the tell-tale LED or incandescent will be receiving fully battery DC voltage, this is why I said do not use the contact breaker side of the coil for its earth.

Les

[Blurredman]

Hi Les,

Thank you- that might be interesting to look at. I will go through my bags of electrics to see if I can rig something up on the fly.

The charge light is never on when riding/idling. It doesn't even come on dimly- It does of course light as soon as the engine has stalled. Which is standard illumination behaviour.

[nice2day]

Hi... you could always use small crocodile clips for the connections as long as they won't fall off. As said, you can use a filament bulb...just solder on the wires to a 12v pilot bulb (5W) and use duck-tape to hold the thing to where you think is convenient location.

Les

[Blurredman]

I like to do my wires properly, les... Proper ring connector with soldered on wire from the coil + to the bulb where I can instantly see it. I would probably use LED light as then I can easily solder it all together. So long as I have 500ohm resistor. I think I only have like 10 or 15 though- Either that or 1k. If I can't find, i'll use the small bulbs that go into the clocks. I have spare bulb holders etc..


As an aside- I am able to restart the bike Immediately after stall and first time too without any throttle/choke input..

Edit:
In fact.. it might just be easier to commandeer the neutral light for this purpose.. so.. in the one clock I can see that if the two lights are on just after a stall then one test has been passed...it could also allow me to see any flickering occurs just before stalling maybe if I always look down at it at lights.

I only need to run one wire from coil positive to the appropriate spade connexion In the headlamp bowl..

[nice2day]

That's good. I only added the quick and easy route as many are put off by doing electrics, soldering etc. Sorry to offend

Yes you would know that using 2x 1K Ohms in parallel makes 500 Ohms....not critical though, it just limits the current to avoid burning the LEDS out or being too dim.

The idea of using the neutral light is excellent (wish I had thought of that) Yes you need to run the wire from terminal 15 on the coil and use a small connector block to the neutral wire....BUT NOTE: you need to remove the bulbs original supply within the headlamp shell (black wire) as the bulb needs the supply from the coil terminal 15 and then you have to earth the same black wire at the headlamp....so maybe do my original idea...it might well be easier

Yes its weird that you can restart so easily but to find out where the problem is you need to eradicate the possibilities one step at a time. What ever remains will be the culprit as Sherlock Holmes would do.

If it is a fuelling problem, I would suspect dirt in the pilot jet circuit. ...Here is a possible phenomena.

At tickover, the fuel flow is maximum through the pilot jet as the vacuum at tickover is maximum (apart from when on the overrun) so if there is a tiny piece of debris this might be drawn into the jets hole. When the engine stops the debris simply sinks down and the flow through the jet can continue and the bike will start. Then after another spell at tickover the dirt reaches the jet hole again and again stops the engine. The cure, as you would know, is to clean out the carb thoroughly by removing the jets and clean carb in ultra-sonic bath.

Les

[Blurredman]

Hi, I just thought the one wire solution might be quickest and neatest to set up Les No.. I didn't take offence- I was just stating that jobs should be done properly with proper connections. It's just connection crimpers are my pet hate I'm afraid- and they fail if not properly done.

I don't doubt there could be crap in the carb.. It's been known and happened to me before. But cleaning the carb (many times) was a process I've already gone through over the years. The fact that the stall/misfire is so sudden at a consistent RPM is what made me wonder more if it was electrical.


Well last night I started wiring up a telltale light, but quickly realised that I couldn't use the neutral light. It's always powered anyway, so it doesn't light until the neutral switch itself makes the earth and completes the contact. So instead I used the high beam bulb. Yes I know about resistences, but I only had 1x 1k resistor.. I do have a broken VHS player I have been meaning to remove all the electronics from....


I didn't really want to use the high beam bulb because for a start it's less wattage (to save it annoying/blinding yourself when using it in the dark country), and not as close to the ignition light so I worried that I might not be able to see it.
But also because I have an MOT on saturday. But on reflection, my MOTs are not standard, shall we say, so that wouldn't be an issue.


But anyway. On the way to work it was fine. But I actually managed to reproduce the problem when I got to work- which is odd because i've never been able to before. Headlamp on and left indicator, and several minutes of idling with it in gear (and clutch lever pulled obs), the bike would misfire every now and then. But not actually stall. On this misfire I could see the ignition (charging light) light brightly for a split second when the misfire occured, but the high beam (coil + ) didn't turn off at all. I then tried right indicator and at first I thought we were grand and it might just be a strange left indicator bulb connection but then it stalled outright with the right indicator. Hi beam bulb didn't turn off at all immediately before, during or after stall.


I did notice that after a while of idling with lights + indicator on, the idle slowed after quite a while to 1200 rpm, and the high beam bulb was having power drawn from it by the indicator relay (fading slightly when the indicator blinks). When the bike was misfiring, and the idle was lower, turning off the indicator stopped the mis-fire and idle increased gradually to 1300.


This points towards the battery it seems (or maybe an overheating/breaking down relay?- I could swap the relay with my other bike to rule that out I suppose. I do recall that I put the current on in around the same time as I started having this problem- could it be? that will be my next test I think...)- i'll have to do another standing voltage test. But my 251 doesn't have this problem. Maybe some variables like different regulators may play a part in this, but with full load at idle both bikes hover around the 10.5v mark, of course the cheap voltage displays they have aren't quick enough to keep up but that's the lowest I've seen and that's perfectly normal for an old vehicle with a full load of accessories.. And actually, I've gone through two batteries whilst this has been a problem.

[Puffs]

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[nice2day]

Hi Puffs. All I was trying to prove was the basic question "Is the coil supply suddenly loosing its supply voltage"?....that's all. My suggestion was to have an easy instant check light. I covered the further testing by saying this:

Of course there might be a fault WITHIN the coil but I have a way to monitor this in real-time too should we need to.... or simply do a substitution.

...I also said let's check one step at a time, I wasn't going to write up a complete page of instructions ....just one step at a time.

A standard LED typically has a forward on voltage of around 2 Volts....Your 12V versions also have a built in resistor...As LEDS can be made to work at any voltage above their forward voltage one usually calculates the dropper resistor value. The 12V ones are designed for 12V and also have a built in dropper resistor. They are more expensive but you could use one of course.

Wiring the LED across the coil would work but then the points have to also pass the current of the LED too.
The reason I said use a proper solid earth is simple...If you wire across the coil terminals and the engine stops and the light is off....how can we tell if the engine has simply stopped with the points OPEN? This is very likely to happen (about 50% chance) and will give no guaranteed indication if the POWER has failed to the coil.....As I repeat....I wanted to find the problem methodically one step at a time. Having ambiguous results will not get to the source of the problem very quickly.

Les