I need to lower my 89 K 100rs. I need to lower it 2-3" I need some advice. I would like to use a shorter shock on the rear and lower the front the same amount but can I go as low as a 11" shock. It has a Corbin seat but I read somewhere that the factory seat is lower. I'm an old dude and need my feet flat on the ground. Any advice would be appreciated........BOB

You can use the K75 low seat setup on a K100.

More here:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/lowseat/lowseat.htm

If you lower the suspension too much it will start to mess with the handling and the pegs will scrape easily.

Bob go out and buy a set of shoe lifts, that will give you anywhere from 1/2" to 1" plus. Then go out and buy yourself a new pair of motorcycle boots with the thickest soles you can find take a tape measure. Try the lifts in the boots before you buy them. that will give you another 1" plus.

Shop around for a GOOD motorcycle seat man all are not created equal. A good motorcycle seat upholsterer can do the following to help 1/ Shave the nose of your seat allowing your legs to move in reducing the distance required to ground. 2/ Lower and repad your seat without effecting comfort. 

You can lower the front forks through the triple trees buy up 1/2" without greatly effecting the handling, and still be able to get it onto the centre stand. Lowering the rear shock as well by 3/4" can be done but you will effect handling clearance and will probably have to modify your centre stand.
Regards Martin.

Martin I already have a shoe lift for my right foot because of arthritis has made my right leg 1/2'shorter but I had not thought of boots with a higher heel and I can get a 12" shock. Is the factory seat thinner than the the Corbin seat? I have cut down seats before but old brain had forgotten that. My kids think I'm crazy for wanting to ride again at 70 and my wife said she knows I'm crazy an the VA said I'm otay so we ride again.....BOB

I haven't had any experience with Corbin seats but somebody will probably chime in. You should be able to find a cheap stock seat that you could play with. There are probably some good seat guys around that could help you, hunt one down, and check out his feedback. I believe adventure boot soles may be even thicker than road boots. You can also have the soles on some boots built up even further. 

I'm 5'7" with short penguin legs and I can flat foot with a standard K1100 comfort seat fitted to a K75. I have modified a couple of seats in the past with varying levels of success. I can now swap between 3 seats. Around town seat very low flat foot with bent legs in work boots. Day trip seat I can just flat foot with bike boots. Long range seat I needs lifts and thick boots to flat foot. 

My forks have been dropped 1/2" through the trees with no noticeable handling problems, slightly harder to get on centre stand which is a K1100 stand.
Regards Martin.

Martin.....just realized that you are from OZ. Would not be here now if it weren't  for two soldiers from  OZ saving  my life in Vietnam.......Bob

I was RAEME attached to Cav. There was a change of Government and we didn't have to go. Honestly I wasn't sorry to miss out. I'm glad you survived.
Regards Martin.