Well you can have one!  And in your K75 too, I suppose.  Of course you can have a 50 amp from a later bike, but I wanted a bit more...

How to mod a K1200 alternator to fit a K100

I replaced the 32A on my 1993 K1100 using the same method but used the front case from a 50A 1995 K75 Alternator which didnt need the spacers.
I bought the 60A knowing it didn't fit but was thinking of making an adaptor ring then found the K75 unit from a burnt out bike and got it for $10 so I got a 60A unit for less than $100AUD including postage from US for the 60A unit.

We have a Seattle area forum member who does the 'upgrade' alternators for K bikes quite frequently. Try K Bike Parts Seattle for details (I'm not affiliated). But I am attempting to mod an R1150RT's higher output alternator from various other bits 'n' pieces for my K100, at the mo'. I reckon the jump from a bog stock, dim bulb 33 amps to a radioactive nuclear glow of 60 amps ought to do the trick quite nicely. 400 Watts up to 720 Watts will be overkill but it's nice to have it.
 

Let me pose a question from one who finds electrons pretty mysterious.  Does this upgrade have any downsides? Excess heat? Danger to regulators or batteries?
It seems incredible that such a huge upgrade could be had so economically... without any downside whatsoever.  

The downside is that it takes more engine power to deliver 60amps instead of 33.
but how often do you need that ?
personally i find the sandard 33amp. Generator quite sufficient. 

K-rider

Regards dangers, electrons, etc., remember -- an alternator delivers power based on the load.  It doesn't just crank out a bunch more amps because you bolt it in.

I've had this argument with a few people over the years.  Bumping up the amp rating of the alternator doesn't require any change to the balance of the electrical system IF the demand is NOT changing.  If you do intend to add load, you need to make the pipes match the flow along the path to that load.

Generally, it's a good idea to replace the feed to the battery and the ground strap, as most loads get wired in downstream from the battery.  If you increase the load from a component, for instance installing an 80w/100w headlamp, then you should upsize those supply and ground wires, and if the circuit lacks them, install fuses and relays.

A larger alternator operating at higher loads will generate more heat, but the location on the K allows for decent airflow, so cooling should not be an issue, at least not in my local climate.  We seldom exceed 90f, one or two weeks in the summer we might see upper 90's or low 100's.  The primary time for higher load is at night (lights) or in cold weather (heated gear), so extra heat from the alternator is compensated by cooler ambient temps.

I didn't do this out of need, I did it because I wanted to, and for the fun of creating the solution.  Next project, how to convert a top case into a 12v beer cooler...   

Like I always say, if it ain't broke, fix it 'til it is...   

I put it on because I run a 100w high beam and 2 x 100w driving lights which gives good light and considering the animals on the roads where I live I need all the light I can get.

Great Mod!!  I liked your link showing great pictures and descriptions of what you did....

I understand about needed lighting, I run extra lights for Deer/Critters as well as for cages wanting to T-Bone me all the time...  In the US we have this thing in October where we go from Daylight Savings time to Standard time, and in the Bay Area, Cage Drivers go nuts for about a month after this...

This past October I was on my airhead, with low wattage output, (I run 2 lights, normal 60W Hi Beam and 55W driving light) and was doing 55 down the super-slab on an on-ramp to another super slab (880 Southbound to the 238 East Bound for those who know), and a fool that was abeam the last chance to make this from the 880 South, slowed, got into the median separating the 2 freeways, and was doing a 90 degree cut from the #1 lane of the 238 freeway on ramp (traffic was stopped behind a big rig who had to stop to prevent from slamming into this fool. and I in the #2 lane barely missed him (Odyssey Mini Van), and I was convinced my lights was the only thing that stopped him halfway thru the #2 lane...

Had to pull over and let the adrenaline go on that one for a bit...

Too bad I wasn't in a big rig, and had taken him out, one less fool behind the wheel sharing the roads with us...

Been riding for 45 Years and that was one of my closest ones yet....

Moral of the story, if I could put a nuclear reactor on the back of my bike, I would, and load it down with lights to it's capacity fore, aft and sides!!!!

Thanks again for the great article and pictures....

I see your point about a nuclear reactor and lots of lights but the flaw is that to see you first of all they have to be looking and like the hens in the hen house there is a distinct pecking order and we are well down the list.
some times I think a rocket launcher would be the best way to deal with them and have an "auto find idiot" function.

Think I might have the answer to that.
Check out YouTube for 'BMW K1600GT hidden function'

That video is very impressive - now I understand why you fancy a K1600 

Yeah, think BMW gets the arm in for the replacement missiles though.

Comberjohn wrote:Think I might have the answer to that.
Check out YouTube for 'BMW K1600GT hidden function'

That was what I was thinking of when I said that John, I really liked that but if BMW has sole rights to rearm then as far as I am concerned it's a one time function. The rearm would be a bit like the O-ring for a space shuttle.

Ringfad wrote:That video is very impressive - now I understand why you fancy a K1600 

One can scroll through the K16's menu for hours and still find new functions. Just one more click of the twisty knob and the radar-operated field mouse counter pops up. Though it too helps relieve boredom on long rides by keeping a rider's road-addled brain engaged, it's a bit less dramatic.
 

ts888 wrote:Well you can have one!  And in your K75 too, I suppose.  Of course you can have a 50 amp from a later bike, but I wanted a bit more...

How to mod a K1200 alternator to fit a K100

today i put a 50A alternator from a 1992 K75 into my 1985 K100RS. had to mod the harness, see picture. the later alternator weighs more, but is way better built, and the modded harness is a much better design. and most of all, my "battery" light no longer comes on whenever i use the brakes or turn on the driving lights. perhaps new brushes and a cleaning would have done the same -- but the later design just feels better in every way. anybody who wants the old 33A alternator can have it for the cost of shipping.

If you can find a way to burn 60 amps then my hat is off to you. I can run a 100W high beam, two 70W fork lights, 36W of heated grips and 90W of heated gear (jacket liner and insoles) on a 50A alternator without issue.

ts888 wrote:Regards dangers, electrons, etc., remember -- an alternator delivers power based on the load.  It doesn't just crank out a bunch more amps because you bolt it in.

Agreed. An alternator only delivers amperage based upon the limits of the VOLTAGE regulator.

It is based upon the voltage, not the amperage.

It's a bit of a misnomer to refer to it as an XX amp alternator because the current it can provide is actually determined by the voltage regulator and the amps an alternator at a particular max voltage.

Hey Mibh, if you still have that alternator I would be interested in it. I know that was of the missing parts to this k100 I bought. I am not familiar yet with the k series bikes to know if I am missing anything else from this pile of metal I bought.