So I bought a Kat 750 shock and plan on installing it when it arrives and would like peoples input...I have been going a little spending happy lately and wanted to put off the front springs and fork oil till maybe the summer.. I am a new rider and a big boy (reason for shock) I weigh around 280 with gear and I'm 6'2....would it be better to do everything at once and wait till summer to install everything? or would it be okay to ride with the shock for a little and upgrade the front later on? where should I mount the reservoir?

With a stiff rear and a squishy front, you'll find yourself flying over on your face.
If I only had money for one change, and your weight, I would have done the front first and set the rear to the #7 position.
The front springs are the main problem. Even reviews of the GS500 in 1989 said the front was crap, while they said the rear was fine.
If you don't change the front, you'll be nose diving into turns and doing stoppies when you apply the front brake. The rear will be in the air and the front on the ground.
You really need to do the front before doing anything with the rear shock.
at my 180 with gear, I changed all front springs. Even for me they were too soft and sagged way to much. The rear shock is fine. One bike I set to 5 or 6, but that's all and that was just to see the difference.

Others may have opinions, but just changing the rear I feel will make the mechanics/physics of the bike really weird.

Replacing springs are as quick as replacing shocks.  You can change out the springs and oil without taking the forks off the bike.  The front springs will give you the most noticeable change for the better, and it will improve handling much more than the shock.

But to answer your question, yes you can change out the shock and upgrade the front later on; however, I wouldn't really recommend it...  to go along with what adidasguy mentions, it may actually make the front end dive worse upon braking and cornering... even stiffer rear suspension with an already soft front.

I did upgrade to an R6 shock before the front springs.  It was an improvement with the settings on the low end, but actually seemed worse when I stiffened it up, even adjusting the damping.  Then a week later my springs came in and I upgraded the front springs.  It was a night and day difference, and made for an excellent upgrade combination.  I'd imagine for a heavier rider, the change would be even greater.

If you still want to put off changing springs, you could at a minimum change the fork oil to a heavier weight.  Which would take little time as well, and offer an improvement over stock.

I will add though that the right way to do it is to take the forks off and drain the oil out and flush with a little clean oil, but if you are time strained, the lazy is way better than not changing the oil at all.  The only issue I see with the lazy way is that it doesn't completely get the old stuff out of the bottom of the fork.

- Bboy

so looks like im gonna pull the trigger on sonic springs...what size spacer would I need I am going to go with the 1.0's...I'm also going to take the forks off and replace the oil should I go 15w?

also about the resevoir on the shock where should I mount it and how?...thanks in advance

Sonic Springs come with instructions. Their web site has a calculator to determine the size you need.

I would guess that most of us have gone to 15w oil just because it feels better than the stock 10w.

Alright so Rear shock is on but not before alot of muscle to remove the bolts...next question how in the world do I adjust the pre-load? I know its on the top but what tool do I need to adjust it?

same shock as this one
http://www.ebay.com/itm/98-99-00-01-07-GSX600F-Katana-600-750-Rear-Shock-B31-15956-/130831652990?pt=Motorcycles_Parts_Accessories&hash=item1e762c987e&vxp=mtr

That shock in the pic is for an 01 Kat 750... The specific part number for the clamp wrench used to adjust that is 09822-00004.
Number 13 in this parts diagram linked below, but not listed as a separate from the tool assembly for purchase.

http://www.bikebandit.com/2001-suzuki-katana-750-gsx750f/o/m147729#sch280637

- Bboy

Edit: A glance at the part diagram for the actual shock... the shock pictured for the 01 kat 750 looks different to the one on the ebay listing.
http://www.bikebandit.com/2001-suzuki-katana-750-gsx750f/o/m147729#sch278840

Quote from: BockinBboy on February 15, 2013, 09:19:07 AM
That shock in the pic is for an 01 Kat 750... The specific part number for the clamp wrench used to adjust that is 09822-00004.
Number 13 in this parts diagram linked below, but not listed as a separate from the tool assembly for purchase.

http://www.bikebandit.com/2001-suzuki-katana-750-gsx750f/o/m147729#sch280637

- Bboy

Edit: A glance at the part diagram for the actual shock... the shock pictured for the 01 kat 750 looks different to the one on the ebay listing.
http://www.bikebandit.com/2001-suzuki-katana-750-gsx750f/o/m147729#sch278840

correct, mine does not have a collar like our stock suspension

Soooo... have a look at the link below, and use it to match the info for the year and model of Kat shock you have.  It notes that many years did not come with the wrench needed for the shock in the toolkit for the bike, and that it was an add-on.

http://katriders.com/wiki/index.php5?title=Toolkit%2C_OEM

- Bboy