1978 GS750 Front Fork Questions

[afraziaaaa]

Picked up some sonic springs and drained oil/pulled out the springs to do the install and found a single long spring. Maybe this bike already had progressive springs in it?

also, my fork sliders just slid right off the upper tube while I had the wheel off. Is this normal for this bike? In my experience with other makes (Honda, Harley) there are usually two bushings on the bottom of the fork tube that prevents that from happening.

Am I missing something here? The photo shows the entire contents of one fork leg.

 

[aclaytonb]

Thats what my 550 looked like when I took it apart.... seems normal. These dont have the copper bushings around the lower part of the stantion like the Hondas. At least, not the 70's bikes from what I understand.

 

[Steve]

It's kinda hard to tell from that picture, but there should have been a bolt through the bottom of the outer tube (accessible just above the axle) into the bottom of the inner tube (shown at the right side of the lower tube). The forks should stay together until that bolt is removed. Some forks I have seen will then slide apart, others will pull the seal out when the tubes are separated.

Back to your first question, it appears the springs are, indeed, progressively-wound, but that does not make them Progressive (brand) springs. Good choice going with Sonic springs, just take a few minutes and set up the preload correctly. In all the forks I have done, the top of the spacer was about even with the top of the fork tube when the forks were fully extended. Compressing them a bit by installing the caps was just about perfect on the preload. You will know the preload is correct when the "sag" is about 15-20% of available travel. Most of our forks have between 5 and 6 inches of travel, so about 1 inch of sag will work great.

You didn't ask, but 10w fork oil works quite well.

.

 

[afraziaaaa]

Ok sounds good. I do have the bolts. I took them them out when I drained the fork oil which looked pretty translucent. Good to know that I am good to go here. I’ll be using 10w.

i should be able to reuse the same seals then since they slide right on/off, right?

 

[Steve]

i should be able to reuse the same seals then since they slide right on/off, right?

In the words of Clint Eastwood: "How lucky do you feel, punk?" You are already down that far, it's only a few bucks more for new seals. It only makes sense to do the job right and do it ONCE.

.

 

[Downs]

^^^ That. You're already taht far into the forks just replace the seals and dust boots.

 

[afraziaaaa]

I'm usually pretty lucky. Now hold my beer and watch this!

Thanks.

 

[hannibal]

Ok sounds good. I do have the bolts. I took them them out when I drained the fork oil which looked pretty translucent. Good to know that I am good to go here. I’ll be using 10w.

So the upper and lower forks didn't separate until you removed the bolts? I've only studied the diagram, but I can't see how the upper and lower could separate with the bolt installed properly.

 

[afraziaaaa]

So the upper and lower forks didn't separate until you removed the bolts? I've only studied the diagram, but I can't see how the upper and lower could separate with the bolt installed properly.

That's correct. They didn't separate until I removed the bolts, so I think all is well. At this point, I am just waiting for my replacement copper washers to show up so I can put the front end back together.

Whoever did the last rebuild (which was recent or has low miles on it) did not use any thread sealant on these bolts. I found some fork oil on the axle, so I want to be sure every precaution is taken in sealing the forks.

 

[hannibal]

Are the copper washers crush washers that are designed to be replaced whenever that bolt is removed? #17 on the parts diagram (behind the "P" in sports)? Guess I should add that to my list of parts.

 

[Downs]

Are the copper washers crush washers that are designed to be replaced whenever that bolt is removed? #17 on the parts diagram (behind the "P" in sports)? Guess I should add that to my list of parts.

They should be replaced but I've gotten away with reusing them before.

 

[hannibal]

Thanks! I found a YouTube that shows how the forks come apart. Feeling much more confident now.

 

[afraziaaaa]

Got the sonic springs in and put about 150 miles on em so far. They are great.

 

[Downs]

I think I went Race Tech on my GS. It's been quite a while since I put them in. They made the bike feel much better having a properly sprung front end. Now I need to dump those dump truck like riding EMGOs off the back and get something else.