GS750E front fork/spring overhaul

[Guest]

Hi all!

So my forks are pitted, leaking oil and don't have that much suspension anymore.. Time for an overhaul! But I have a few questions:

- What's the size of the tool you need in the fork to keep the dampening rod from turning? Some places I see 19mm, others I see 24mm... Also: What do you guys reckon is the best option for a selfmade tool?

- I am going to replace my fork seals (obviously), but what other parts would you guys suggest to replace? If they're all apart, I might as well get them properly done.

- The tubes are pitted, so I found a place to get them rechromed for about 75-100 euros per tube. Seems ok, especially since I can't seem to find replacements for that amount of money. Anything to be aware of with them?

- What new springs to go for?:

I thought I had decided on the progressive springs as I saw quite some positive stuff about them, but just now I saw many guys here are going for Sonic springs with the cartridge emulator... My goal is to get the bike on the road again as a tour bike, not something for a race-track. With the progressives I'm scared for them becoming too squishy, because I do like to feel the road and feel I'm riding a bike, not a comfortable sofa XD
On the other hand, I do want to get a nice tourer so a smooth ride is preferred...


Anyway, looking forward to getting the forks done. The better the weather becomes, the more I miss driving the old one. The newer bike is fun, it's just not the same thing ^^

[azr]

Buy the Sonics, the correct ones for your size/riding, the site will direct you. You don't have to do the emulators by no means. There's nothing else to replace but your seals, too bad about the fork tubes, isn't there someone on the site here that has an extra set to sell you?? I have a shed full but I can only imagine what shipping would be. There's a thread on Basecliffs site on how to make the tool you need out of threaded rod and 4 nuts.

[Drummert]

Funny, I am (as most of us I guess) a frequenter on his site, but apparently I overlooked this one. Thank you! Also, I think I will end up going for the Sonics indeed. I am very afraid of the change of the characteristics would I go for progressives.

Yeah, those tubes seem hard to find here. I did not try on this forum, but since I found a place to get them redone I might as well go for that. Shipping a set of tubes from the U.S. will be quite expensive, so this might actually be a bit cheaper. It does stick with my idea of trying to use as many of the original parts of the bike. As soon as they're done, I'll just put some fork gators on there to keep them clean.

Right. Little check on Basscliff's site, little tour around the hardware store and then time to get those forks out I suppose!

[mmattockx]

Also, I think I will end up going for the Sonics indeed. I am very afraid of the change of the characteristics would I go for progressives.

Your OEM springs are progressively wound, there is no noticeable characteristic change through the suspension stroke as compared to straight rate springs. The only significant problem with the OEM and Progressive Suspension fork springs is that the rate is way too soft and this results in poor suspension performance. The Sonics are not magic, but they are available in the correct spring rates and this is why they perform so much better than stock or PS. Note I'm not dumping on Sonic, I have them in my 1100E and they work very well, plus service from Rich at Sonic is excellent and his prices are very reasonable. But people seem to attribute magic to straight rate springs as compared to progressive wound springs and that just isn't so. For our purposes there is no functional difference between the two as long as you can get the correct spring rate.


Mark

[Darin Jordan]

Interesting comments. I rebuilt the forks on my 1980 GS850GT about 4-years ago, but am looking at putting in a set of Emulators and possibly new springs. Presently have the Progressive springs. Find them to be a tad soft with more front end dive than I'd like. Looking into the Sonic springs right now.

Anyone have a recommendation in spring rate for a "Sporty" ride? I often go for long rides on the freeway, but want the performance to be "sporty" for the twisty stuff.

[Drummert]

Your OEM springs are progressively wound, there is no noticeable characteristic change through the suspension stroke as compared to straight rate springs. The only significant problem with the OEM and Progressive Suspension fork springs is that the rate is way too soft and this results in poor suspension performance.


Mark

This clears up a lot. I thought the OEM springs where straight rate with only a small part at the end with closer loops. The softer suspension with more dive was what I was afraid of, so this makes things a lot easier!
I took the forks off today, will take the forks themselves apart somewhere this weekend or next week. I drained the oil already, where I found only a little oil, less in one of them and in that one green where in the other it was pitch black. I guess this wasn't a moment too soon.

Pictures in my thread in the projects/rebuilds!

[cowboyup3371]

Darin, Rich has a calculator on the Sonic Springs website where you can select the way you ride and general weight on the bike (rider, tank bag, etc.) to reflect the different spring rates. Click on the Find your Spring Rate link on the left side of his main page (www.sonicsprings.com)
and enter the values:


Riding Style:
Racing – self explanatory
Aggressive Street – Hard street riding, including heavy braking and aggressive riding in the twisties.
Normal Street – Some hard braking, not as fast in the corners.
Relaxed Cruising/Touring – Moderate pace, no hard cornering.

Spring Rate Calculator
Select your bike type:			Select your riding style:
Sport Bike			Racing
Standard/Sport Touring			Aggressive Street
Cruiser			Normal Street
			Relaxed Cruising/Touring

Enter your weight with gear: lbs.

Enter your bike's weight with a full tank: lbs.

Tank bag? Yes No

[mrbill5491]

I'm pretty sure you don't need a fork leg tool with the nut set up on the 750. All you need is something with a tapered end to jam into the rod to hold it. My 80 750 forks were that way. When I converted to the 1100 fork set up then I needed a tool and made one myself out of some rolled steel rod. I welded a 19mm nut to the end and made the whole thing in to a long T handled tool. Works really well. Oh yeah, check the slider bushings at the top of the outer fork tube, those have to be replaced at times, as well as the slider bushings on the bottom of the inner fork tubes.

[Drummert]

I already bought some threaded rod and some 19mm nuts to get the job done. I'll see if I need them ^^ I'll check the slider bushings as well. I expect them to be in a bad shape, judging from what I have found in other places of the bike...

[Drummert]

So, I took the forks apart today. Here are my findings, pictures below:

- There are springs in there measuring about 510mm, so those are not the standard ones. I think these are progressive springs, but no idea how old and in what shape... More on this after this list.
- There was no spacer in the forks. Is this actually right with the progressive springs or should that have been in there anyway?
- Both my dust covers were so dry, they broke taking them off.
- Underneath one of the dust covers, I found some very nasty smelling stuff what almost seems to be a piece of cloth? Or maybe hard residue from the fork.. I had to take it out with a screw driver.
- I didn't need the tool (as you guys already said). Clamping it in the workbench with a towel around it and loosening the allen head bolt underneath was all I needed.
- Everything is really dirty. Whats the best way to clean everything? I'm afraid using degreaser harms the teflon coating of the bushes.
- The tubes are badly pitted. I checked to see if it wasn't just dirt, but they are rusted and I need to get them rechromed. There is a bushing in the inner tube, right? How do you get those out? I wasn't yet able to and I don't want to harm them. But I guess they'll have to come out for the rechroming.
- How do I actually know of the teflon coating is still ok? Does it just need to look ok?

Also, I'll have to look for a good way to take the oil seals out without harming the forks and the bushing underneath...

With my finding of the, I'd guess progressive, springs already in there, I started to doubt whether I should replace them. They are not the standard springs anymore, are longer than the originals and I thought the bike did ride nice before the oil seal blew. On the other hand I have no idea how old they are and you guys seem to like Sonics better, which I regard as expert advice. I already sent an email to them and got a very nice response back from Rich who confirmed my found spring rate as well. Decisions, decisions...


Sorry for asking some stupid questions with obvious answers, but I'd rather get it right the first time than harm the bike and needing to find new parts ^^

Picture time! Springs already in there:






The mess hidden beneath the right dust cover.

[mmattockx]

- Underneath one of the dust covers, I found some very nasty smelling stuff what almost seems to be a piece of cloth?

That almost looks like the fork seal was weeping a bit and the owner jammed a rag under the dust cover to collect the leakage.

- Everything is really dirty. Whats the best way to clean everything? I'm afraid using degreaser harms the teflon coating of the bushes.

Kerosene is OK for the seals and bushings.

There is a bushing in the inner tube, right? How do you get those out? I wasn't yet able to and I don't want to harm them. But I guess they'll have to come out for the rechroming.
- How do I actually know of the teflon coating is still ok? Does it just need to look ok?

You have to completely disassemble the forks and pull the inner tube out of the outer tube. When you take the damper rod bolt out and pull the inner tube out of the outer tube it will pull the bushings and seal out with it. You often have to put the outer tube in a vise (clamp it on the caliper mounting lugs) and use the inner tube like a slide hammer to pop the seal and upper bushing out. You can usually look at the bushings and see if the coating is ok, but my policy is to replace them unless I know the age of the bushings in there. They are cheap and there is no point in saving a few pennies on these.


Mark

[hillsy]

Quite a common thing "back in the day" to put some rag underneath the dust caps as extra protection for the seals, although, in this case it might have been to soak up the oil from an already leaking seal.

[Drummert]

You have to completely disassemble the forks and pull the inner tube out of the outer tube. When you take the damper rod bolt out and pull the inner tube out of the outer tube it will pull the bushings and seal out with it. You often have to put the outer tube in a vise (clamp it on the caliper mounting lugs) and use the inner tube like a slide hammer to pop the seal and upper bushing out. You can usually look at the bushings and see if the coating is ok, but my policy is to replace them unless I know the age of the bushings in there. They are cheap and there is no point in saving a few pennies on these.

Yes, I did take them apart already. Thing is: I turned loose the damper rod and took it out. After this, I expected the inner tube to catch on the bushings and seal of the outer tube, but it just went out. No bushings along with it. Seal still in the outer tube. So, this made me wonder where the bushings should be actually. On a drawing at cmsnl I can see two washers underneath the oil seal (although I'm not sure these are the bushings). Other than that, I don't see other bushings than the one on the damper rod. Could it be there's only the bushing on the damper rod on this model? I thought It should have a bushing on the damper rod, one around the lower end of the inner tube and one under the oil seal in the outer tube?

Quite a common thing "back in the day" to put some rag underneath the dust caps as extra protection for the seals, although, in this case it might have been to soak up the oil from an already leaking seal.

It might have been both. The one thing i'm sure of is it spent quite some time there :P

[mmattockx]

After this, I expected the inner tube to catch on the bushings and seal of the outer tube, but it just went out. No bushings along with it. Seal still in the outer tube. So, this made me wonder where the bushings should be actually. On a drawing at cmsnl I can see two washers underneath the oil seal (although I'm not sure these are the bushings). Other than that, I don't see other bushings than the one on the damper rod. Could it be there's only the bushing on the damper rod on this model? I thought It should have a bushing on the damper rod, one around the lower end of the inner tube and one under the oil seal in the outer tube?

I'm not sure on the bushings then. Every fork I have pulled apart has had a pair of bushings as you describe. I know some of the older forks only have one bushing and I think it sits at the top of the outer tube. I have never pulled one of those apart, though. For getting the seal out you can screw a couple sheet metal screws into it and use them to pull it out, along with a large flat screwdriver to pry (gently) under it once you have it moving. Once the seal is out I expect you will see the bushing. There is no bushing between the inner tube and the damper rod.


Mark

[Drummert]

Hi All!

Some time ago already. I guess these things happen. I am back at doing some stuff on the bike again.

Today I started by checking the tubes again for the bushings. For as far as I get it now it is one bushing at the top in the outer tube, below the fork seal, one on the bottom of the inner tube, actually inside of the inner tube where the damper rod slides through and one on the damper rod itself. Problem that arises here is: the inner tubes need to get rechromed (still.... after a good 5 months... poor things) and as far as it looks there is no possible way to get that bushing in the inner tube out. It seems to be between two ledges where it turns around freely and has some wiggle, but I don't see any way of getting it out.

Also, I really have a struggle with my fork seals. After trying small screws (that did not go in in any way), gently prying them out (nope), using heat from a heat gun (smoke yes, pop no) and then after heating them up trying a little tool made out of a very flat bolt that ledges into one of the ledges and a weight to hammer it upwards it only came out in small (read 1mm big) pieces.... Now I do understand there is some metal in the seals... question remains now which is which... I can't really see a difference anymore and have part of the rubber out, part of the rubber still there.. Should it be flat on the inside of the outer tubes? Doesn't look like it in videos and all...

Picture of the fork seal/outer tube problem:



Picture of the inner tube bushing problem: