83 Kz550 rear shocks/spring = donkey kick in the back

Very new to this bike as I just took it from pieces in a box to a running/riding motorcycle again. First thing I noticed was how sharp any significant bump/hole is on the back suspension. Front eats it fine. The back literally jolts by ass through my spine into my neck.

Is there anything that goes bad internally on these that would cause it to stiffen up?

It's already on the softest setting. Not sure what else to do here. Aftermarket options?

Thanks!

I bet somebody replaced the crappy factory shocks with some for a much heavier motorcycle. On most KZs, the factory shocks were crap when installed at the factory and deteriorated from there very quickly. If those are original to the bike, and you weigh more than 42lb, the rear suspension would likely bottom out over every paint stripe on the road. Could that be what you ar feeling?
Have you had a friend help measure sag?

I am not familiar with the options for the 550, but I would probably look to Hagon or YSS. If you want the absolute best, and are willing to pay for the best, check Ohlins.

thanks for the quick reply and insight. Ill check to see if they are oem, but I bet you are correct that they have been swapped from another bike. I havent checked sag, but when I sit on the bike, the rear shocks do not compress even 1/4"

I weigh 165 without gear

If I stand over the bike and push down over the rear wheel, I can get the suspension to compress maybe 3/8 to 1/2 inch.

Yup. Those springs at too stiff.

As Texas said, someone put on some crappy shocks. I think I had those same ones for about 15 minutes. I had to get rid of them immediately as I felt it was dong damage to the frame from being so harsh.

But to answer your question about stock shocks... they are probably all no good nowadays. The dampening washers which were plastic turn to finely grated cheese. It seems like a chemical breakdown. The stock springs usually stay ok. I still use them.

Get a decent set of Progressive 12 series and the bike will be a lot nicer.

Stock rear was about 13.75" from eyelet center to eyelet center.
Progressive 12-1207B is 13.5”

I install the original factory spring with the Progressive shocks. I just have to modify the OD dimension of the spring a tiny bit to fit.

AdvEvryWhr wrote: Very new to this bike as I just took it from pieces in a box to a running/riding motorcycle again. First thing I noticed was how sharp any significant bump/hole is on the back suspension. Front eats it fine. The back literally jolts by ass through my spine into my neck.

Is there anything that goes bad internally on these that would cause it to stiffen up?

It's already on the softest setting. Not sure what else to do here. Aftermarket options?

Thanks!

Those look like the same progressive shocks I have. Got them for under $200 and am very happy with them. I dress out at 200+ and the bike is much heavier than yours. They are rebuildable but in your case it would be about the same to buy lighter shocks. Maybe sell the ones you have to defer some of the cost.
Steve

The ones in his photo look like the MDI Forza shocks I had and were waaaay too stiff for a 550.
I think you're right Steve, I think they would work well on a 1000. I gave them to a buddy with a 750 and they were too stiff for him, even though he still used them for a while. They were not usable on my 550.

Disambiguation: "Progressive" can describe the shocks, but unfortunately it is also a brand name. I was suggesting he get the Progressive brand's 12-series shocks.

thanks all! Leaning towards the progressives after the advice here and a reviews I have seen. Thanks again for the insight!

I am suffering the same problem. What did you go with? This is what was on mine when I got it back. Just noticed yours is an LTD. That probably is different application than an A2.