Why do XS11s have ballast resistors?

[Incubus]

This question is more out of curiosity than anything else and I've wondered about this for some time. I can rewire my bike, but I still consider electricity to be nothing short of magic....

Stock coils on my '79 Standard are 1.5 ohms and there are 1.5 ohm inline ballast resistors. I know adding the resistors cuts down on the amount of draw on the electrical system, but doesn't it also cool off the hot spark generated by the really hot 1.5-ohm coils? And, if this is the case, why didn't Yamaha go with 3.0-ohm coils to begin with, like it did with the later models. I haven't known Japanese bike makers to unnecessarily add to production costs, so I figure there had to be a reason they chose to use these coils with resistors when they could have gone with cheaper (?) coils and no resistors saving a few bucks on each bike.

Any electrical gurus who can help me understand the benefit?

Patrick

[Incubus]

And what would happen if I tried to run without the ballast resistors? Just problems charging, or would there be other bad side effects?

[crazy steve]

That was really kind of a holdover from point ignitions. When this bike came out, electronic ignitions were the 'latest thing' and their thinking was still tangled up with the older ignitions. The reason for the ballast resistor was to have a hot spark for starting, but if you had points, the higher current reduced point life significantly so switching to running the coils through the resistor helped. In this case, the TCI box couldn't take the higher 'starting' current for more than a few minutes. A lot of the early electronic ignitions worked this way. But they found that degradation of the spark was nearly non-existant over time (unlike points which wore) so this 'boost' during starting wasn't needed. Ballast resistors joined their cousins points in the obsolete parts bin...

'78E original owner

[cowboybob998]

And what would happen if I tried to run without the ballast resistors? Just problems charging, or would there be other bad side effects?

I would like to know the answer to this question myself, someone here on an earler post stated you could just unplug the ballast risstor and plug the wires together, not brave enought to try this yet without more information, dont want to fry the tci.

[natemoen]

I think if you unplug the ballast resistor and run the bike over a long time like that you will burn out the coils and or the TCI. From what I understand you can unplug it for a short time to see if it is the problem but you can only run that way for a couple minutes max.

[DGXSER]

Thinking abut it from my logical viewpoint (however logical that is), the ballast resistor offers of course reistance to the flow of electrons going to the coils. creating the total of 3 ohms between the two. During starting, the ballast resistor is bypassed and the full flow goes to the coils.

So, yes, it will run for a short time without the ballast resistor as it does eveyr time you start it. But I would suspect you will burn out the coils running it like that for a longer period of time. I am not sure how it would effect the TCI, as it is upstream of the ballast resistor and the coils anyway.

[crazy steve]

And what would happen if I tried to run without the ballast resistors? Just problems charging, or would there be other bad side effects?

If you have the 1.5 ohm coils and disconnect the ballast resistor, it will kill the TCI if you run it very long. When not in starting mode, the coil/ballast resistor combo has a total resistance of 3 ohms, so draws half the current the coils alone draw. Switching to 3 ohm coils will allow you to eliminate the resistors.

'78E original owner