Changed fork seals and oil. Now dampening feels very stiff.

[Spiff]

1980 Gsx750, new to me, haven't ran in 5-6 years, Got it running a little while ago.
​​​​​​Leaking forks. Replaced seals, put in some 10w fork oil. Problem is now the suspension feels stiff and harsh on low speeds around 30-50kph. Riding at higher speeds feels alright. Any tips?
I follow the instructions in the service manual regarding oil level. It also said atf:motor oil mix but I went with 10w...

 

[Suzukian]

I'd go with the ATF. Once you increase the viscosity, this is what happens. You could go down to 5 weight and see what happens.

 

[Nessism]

10w fork oil is fine. You might want to measure oil level, with the forks fully compressed, and the fork springs removed. The 750E model fork level should be 9". If you still find the front end too harsh, try 7.5w oil, and go from there. It might be, though, that you just got used to having no damping...

 

[Suzukian]

Nessism​, you think that he had no dampening, and now, having put in fork oil, has some, so the bike seems stiff? I hadn't even thought of that. I guess that's why I read everything you post. Great catch. Much respect.

 

[Spiff]

10w fork oil is fine. You might want to measure oil level, with the forks fully compressed, and the fork springs removed. The 750E model fork level should be 9". If you still find the front end too harsh, try 7.5w oil, and go from there. It might be, though, that you just got used to having no damping...

just came back from a ride in the dark and you can literally see the light bounce up and down.
9" is like 229mm or something like that? I put mine at 242mm from what it said in the service manual I have, There where two different levels and capacities depending on what model you had, there was also two different spring lengths and both had two springs in the fork, but my fork only has ONE spring, and a metall spacer.

I haven't ridden this bike except for a small test ride when I first got it running so I don't think I've gotten used to anything, but I also haven't ridden a stock GS in like forever so I'm not sure how it should be.
what about tires? could that be an issue? I put brand new tires on, they are balanced but idk.

 

[Rich82GS750TZ]

just came back from a ride in the dark and you can literally see the light bounce up and down.
9" is like 229mm or something like that? I put mine at 242mm from what it said in the service manual I have, There where two different levels and capacities depending on what model you had, there was also two different spring lengths and both had two springs in the fork, but my fork only has ONE spring, and a metall spacer.
.

Just a guess: If the service manual to which your are referring doesn't match what you are seeing, I'm going to suggest the possibility that you may have on your bike a pair of forks that did not originate on your bike. Either that, or you have the wrong service manual for your bike/forks.

 

[Spiff]

Just a guess: If the service manual to which your are referring doesn't match what you are seeing, I'm going to suggest the possibility that you may have on your bike a pair of forks that did not originate on your bike. Either that, or you have the wrong service manual for your bike/forks.

When browsing the parts diagrams over at cmsnl.com and I choose a EU market 1980 gsx 750 the drawing shows a fork with one spring and a spacer(available in two lengths). And the bike is to the best of my knowledge original.
So idk about the forks in the manual, I have browsed the 750 manuals on bike cliff website but they show the same two spring forks or a antidive fork(also with two springs)

 

[garyS-NJ]

Overfilling can make the front end harsh. Perhaps your oil level is wrong bc 10wt fork oil should be fine.. otherwise with the wheel off and springs out I would check that each lower leg slides smoothly on the inner fork tube.

 

[bitzz]

A spring with a metal spacer SCREAMS aftermarket. Did you set the sag?