Idling speed

[Guest]

HI,
I have just started this thread to get some comments and experience from the other memebers.
Yesterday I left my lights on, on my small van and the battery went down. After jumpstarting it the idle was quite rough, untill I realised that the load on the alternator charging the battery was being felt by the small engine. After a short trip everything was back to normal. A 60 or 90 Amp alternator pushing out high current to a flat battery does put some extra load on a small 100hp engine. On some vehicles the idles also drops slightly if you put all the headlights on drawing about 20 Amp and then also touching the brakes and adding a few more.

I have had personal experience where my bike idles at just under 1000rpm when hot, such as riding a short distance at 20-60km/h. Then I do a 15 kilometer run at 80 to 100km/h and the bike idles just under 1200 rpm. I did put this down to engine temperature, but was wondering about alternator load to a partially flat battery and then to a fully charged battery.

On the forum I have seen some comments on rough idling and batteries/charging systems being bad. Someone recently posted that after replacing his R/R the bike idles better.

The first question now is:
Is there a heavier load on the GS engine during idle caused by the alternator/stator if the battery is discharged or if the R/R is faulty and loading the stator?
Second question:
Will this be noticeable to the rider?

Someone my have experienced this.

[rustybronco]

HI,
I have had personal experience where my bike idles at just under 1000rpm when hot, such as riding a short distance at 20-60km/h. Then I do a 15 kilometer run at 80 to 100km/h and the bike idles just under 1200 rpm. I did put this down to engine temperature, but was wondering about alternator load to a partially flat battery and then to a fully charged battery.

The first question now is:
Is there a heavier load on the GS engine during idle caused by the alternator/stator if the battery is discharged or if the R/R is faulty and loading the stator?
Second question:
Will this be noticeable to the rider?

1. No the alternator on your bike is not like the alternator on you vehicle, your vehicle has a "adjustable" field coil that provides the magnetic field for the stator, this will vary the load the alternator places on your engine.
your bike has a permanent magnet for the magnetic field, thus the "load on the engine" will remain constant for a given rpm. the excess wattage not used is given up as heat in the r/r.

2. No

[mikluha]

....your bike has a permanent magnet for the magnetic field, thus the load will remain constant for a given rpm. the excess wattage not used is given up as heat in the r/r.

I would disagree. Even with the permanent magnet the load on the engine depends on the load on the stator (it a simple energy conservation law) unless there is an excess that is dissipated in the r/r. But as far as I know r/r kick in only around 2.5 k and there is no excess at low rpm.

[rustybronco]

amended my statement from load, to "load on the engine"

The alternator is a wattage output device, the loads are the battery, lights and the electrical devices on the bike.
what wattage is not used to recharge the battery and run the devices on the bike is given up as heat.

[Matchless]

1. No the alternator on your bike is not like the alternator on you vehicle, your vehicle has a "adjustable" field coil that provides the magnetic field for the stator, this will vary the load the alternator places on your engine.
your bike has a permanent magnet for the magnetic field, thus the "load on the engine" will remain constant for a given rpm. the excess wattage not used is given up as heat in the r/r.

2. No

What brought up this thought was that when I was at school I had an old handcrank telephone generator with an armature and permanent magnets and if you shorted the output the handle was harder to turn and I would have guessed that at maximum current it would be harder to turn. If the bikes alternator is always pushing out "maximum" current, either to the load or shunted to ground then it would then only idle faster if the regulator or stator is faulty and the current is going nowhere?
Thanks for the reply.

[Matchless]

OK, if the load on the engine is constant then pulling the 3 leads from the stator should disconnect the load and get the idle to rise or have I missed something? I wonder if this will be noticeable? Unfortunately my motor is apart and I cannot do a practical test.
Thus back to the original issue, if the regulator is not regulating properly or intermittently or a connector is not making good contact then theoretically the idle can be affected?

[rustybronco]

Thus back to the original issue, if the regulator is not regulating properly or intermittently or a connector is not making good contact then theoretically the idle can be affected?

at low rpms the electricals are running mostly off the battery, I don't think you would be able to notice the difference.

[Matchless]

OK, thanks I think that puts that thought to rest.