Rear shocks

Hi, everyone. New to the forums. Hopefully, just a simple question about shocks.

I've done some research and it appears that I want to put a set of Progressive 412 series shocks on the back end. The current shocks are STOCK (1979 SR650) and can't handle the weight of myself, let alone with my wife leaning back on the sissy bar. Our combined weight is about 350 lbs. (225 for me, 125 for her). I cannot adjust the preload. It's on the third notch and is rusted in place.

I've thought about the heavy duty version (rate 90/130 versus 75/120 for standard). Question is: will the standard rate be sufficient or is my behind just too wide and I need the heavy duty springs? The current springs are 31 years old and, even though there is only 6900 miles on the bike, the spring are tired enough that I can sag the rear end 2" by myself.

Also, if anyone has a better suggestion for shocks (12 series? or another brand, I like the look of the 412 series) I'm all ears.

These guys make some nice shocks.

www.worksperformance.com/html/home.html

I went with progressive (brand) rear gas shocks and progressive springs on my 750 and they work great. I went with the standard spring weight but I never ride a passenger and I only weight 175. I would GUESS that you would need to at least go up to 90/130 for your total 350 lb loading. I would have thought even higher (?) You should call the guys at Z1 Enterprises, they know a lot about this stuff.

The stock springs your bike came with (and mine) are total junk regardless of age or miles.

Here's another option:

Hagon

Dave Quinn will set up the new shocks specifically for your weight and riding style There are a number of different configurations available. I really like mine. Here's a thread that shows a pic of them on my KZ650C1:

Pic

My KZ1000st has progressive fork springs with some valving modifications and 12 series shocks on the rear.Started with 120/170 springs which were way to stiff.Now it has 90/130's with the preload cranked all the way up and is still to soft.Will be switching to the next heavier spring.I know the st is heavier and I do ride with some "enthusiasm",but it should give you an idea of what to look for.
I raced circle track and learned a few things about shock valving and spring rates.

I suggest 12 series(more fluid volume for 2 up riding).
13" eye to eye.
Next heavier spring from 90/130(with 5 preload settings you can ride solo on less spring pressure and adjust in more as needed.
How about your forks and steering stem bearings?

All good comments. Thank you.

The forks and steering stem bearings are part of my winter over project. The dust covers are wrapped in Scotch 130 because they've split and the seal on the right side is leaking. The upper tubes have mild pitting. Not sure if it's enough to warrant replacement. The fork springs are being replaced at the same time. I figure it'll be a winter over project because it will most likely be an overhaul of the entire front end.

The Hagon shocks look very tempting, too, for about the same price range. I definitely won't buy a set before talking to those guys.