Hi I believe it's possible to upgrade your charging system by using the outer case
etc of a 33 amp alternator and the inner rotor etc of the later 60 amp alternator has any one done this or got any advice on this ?cheers .

Copied from Euromotoelectrics.com:

Original Equipment New BOSCH 50 amp alternator for K1, K75, K100, K1100 1983-99, and R Series 1993-2006 with 700 watt / 50 amp alternator. Also replaces 450 Watt / 33 amp unit on earlier K models. This alternator has 50% more amperage output than the original Bosch alternator 1983-1988 K100/K75 applications.

Technical Information: Brand new OE BOSCH alternator will also retrofit earlier K models with 14V 32 amp alternator. This retrofit will require adaptor kit with new alternator clutch housing (BMW # 12 31 2 305 329), driving dog (BMW # 12 31 1 460 304) and rubber mounting dampers ( BMW # 12 31 1 464 877 x 3).
This works a charm!

This is only worth doing if there is a problem with your existing alternator or you run a lot of accessories like extra driving lights or fog lights and or heated clothing. If you just fancy one that's ok too but for most people this is not a need to do item.
Regards,
K-BIKE

It's true that for most of us the 'upgrade' isn't necessary. I went to the 400 watt alternator on my old 280 watt (at best) Airhead. A good battery, properly maintained, should suffice for our mighty K's, unless you're powering a 'doof doof' amplifier and subwoofer for late nite cruizin' down the mean streets.

Thanks for your advice ,cheers Ian .

TWB raises a very good point the Airheads had very marginal output so for them an upgrade is well worth doing. Hardy souls who ride their K's throughout the North American continent winter need lots of heated clothing and if they run extra lights then an upgrade is worth it.

Or of course as TWB says if you have the full on cruising posing machine with big sound system then it is a must because they are only of use for cruising slowly down Main Street with the sound blasting to impress the locals, then low revs big draw a big alternator is needed :-)
Regards,
K-BIKE

If you are still looking for a 50amp alternator you could try
kbikeparts.com he sells them fully reconditioned for $150.00
I haven't purchased anything from him but he has steered me clear
of a couple of bad purchases I was going to make and seems like a good guy, encyclopedic knowledge of K bikes.

Thanks Chris ,See you've got a cb450 been on one but never owned one,Did have a Honda xbr 500 though cheers Ian .