Fork Oil Replacement

[Guest]

I would like to change the fork oil on my GS650G. The shop manual instructs you to remove the forks, invert and empty the fluid. Then fill with a "Fork Level Gauge" with spring removed and fork compressed.

Is that all necessary? Do I have to remove the fork? Can't I drain them via the drain holes at the bottom of the forks? And, do I really need to refill with a Fork Level Gauge?

[cowboyup3371]

Have you been to Basscliff's site lately? He's got three very good tutorials on working with the forks.

Here's one:

http://members.dslextreme.com/users/cbsaunders/gs/Fork_Seal_Replacement_GS850GT.pdf

[snackie]

Nice tutorial but I don't need to replace my seals. Just wondering if i can change the oil without removing the forks.

Thanks.

[cowboyup3371]

You'll want to do all of it at least the first time to make sure they are good.

However, your other questions were answered in that tutorial on how to refill them. It's something that has to be done through the top anyway so might as well do it all the first time. Honestly, it's easier so you won't have to worry about stripping that screw

[bwringer]

Nice tutorial but I don't need to replace my seals. Just wondering if i can change the oil without removing the forks.

Thanks.

If you have drain screws, you can change most of the oil without removing the forks. You won't get anywhere near all the old oil out.

Once you see and smell the horrible chunky eldritch ooze that emerges, you'll probably understand why it's a good idea to remove the forks and get all that crap out, at least if it's the first time it's been changed in a few decades. It's not all that much extra work.

At the very least, you might want to try and flush things out. Dump in some cheap ATF, pump the forks a bit, then drain the resulting sludge. Repeat this a few times until it starts looking less disgusting.

[Steve]

Yes, you can use your drain screws, but as Brian (bwringer) said, as soon as you see what comes out, you WILL want to do it properly.

By the way, you don't "fill with a fork gauge", you merely use a fork gauge to adjust the oil to the proper level.

You may think that you don't need to change the seals. How did you come to that decision? Was it because the forks are not leaking? Did you stop to think that maybe they are not leaking because there is nothing in there to leak out?

Because you are asking these questions, it is obvious that you do not KNOW the condition of your forks. As mentioned (several times, now), at least on this first time, do the job right, it might be the first time the fluid has been changed in the last 30 years. After this, you will KNOW what is in there, and can feel a bit more comfortable with a simple 'drain and refill' session next time around.

Removing the forks is not that big a hassle.
- Remove the wheel.
- Remove the fender.
- Loosen the triple clamps.
- Slide the fork UP , then re-clamp one bolt.
- Loosen fork cap, but don't remove it.
- Re-loosen clamp, slide fork tube down and out.

There is no need (usually) to do anything with the headlight or wiring. The fork tube will slide down through the ears that hold the headlight, everything will stay pretty much in place and is easy to re-align when sliding the fork tube back in.

.

[JTGS850GL]

Also, the brake calipers will need to come off the forks and hung as to not put strain on the hoses.

Not trying to thread jack here. Just trying to add discussion on this topic since I'm getting ready to do this tomorrow. What is the best method for screwing the top caps back in without cross threading while compressing the springs? I've heard about pre-aligning the threads but is there any other secret to getting these back on safely? How much tension should I expect on the 850L forks?

[tkent02]

At the very least, you might want to try and flush things out. Dump in some cheap ATF, pump the forks a bit, then drain the resulting sludge. Repeat this a few times until it starts looking less disgusting.

Better yet, put in the ATF and ride it a few days. But even better is to take the extra ten minutes to take it off the bike and clean everything out. It's really easy on these old damper rod forks. When you put it back together, add cartridge emulators.

I don't replace seals that don't leak, as old seals slide easier. Also new seals leak sometimes.

To start the threads, use a socket and a long extension, it helps to hold the top cap straight while you push down hard enough to engage the threads.
An old school speed wrench is even better.

Be careful not to cross thread the drain screw. A lot of them have been cross threaded or at lest started crooked before.

[JTGS850GL]

To start the threads, use a socket and a long extension, it helps to hold the top cap straight while you push down hard enough to engage the threads.
An old school speed wrench is even better.

But what do you do if you have the top spring caps with the air fittings? There is no hex bolt on the top of them to put a socket onto. All I can think of is clamping the forks in a vise or in the tripple tree and then, using your hands, press down while turning it till it catches. Sounds like a bit of a PITA. It's one reason I was delaying this part of the restoration/resurrection.

[Steve]

Not trying to thread jack here. ... What is the best method for screwing the top caps back in without cross threading while compressing the springs? I've heard about pre-aligning the threads but is there any other secret to getting these back on safely? How much tension should I expect on the 850L forks?

To start the threads, use a socket and a long extension, it helps to hold the top cap straight while you push down hard enough to engage the threads.
An old school speed wrench is even better.

But what do you do if you have the top spring caps with the air fittings? There is no hex bolt on the top of them to put a socket onto.

As you hinted in the first post, you need to pre-align the threads. To do that, put the fork tube in the triple clamp, leave the springs out, screw the caps on about one full thread. Now unscrew the caps slowly while pulling them UP. Note where the last thread disengages. Mark the cap where the gap in the clamp is, then put the spring in. Align the cap just a little bit to the left of the mark, knowing that the first 1/4 turn will start to engage threads, then continue from there.

How much tension? Not all that much. I think I had to push down about half an inch. You can use a 32mm socket to push and turn.

.

[tkent02]

But what do you do if you have the top spring caps with the air fittings? There is no hex bolt on the top of them to put a socket onto. All I can think of is clamping the forks in a vise or in the tripple tree and then, using your hands, press down while turning it till it catches. Sounds like a bit of a PITA. It's one reason I was delaying this part of the restoration/resurrection.

Yeah, they are harder, but if you are using air you probably don't need so much spring preload?

Usually if you are stubborn enough and use enough magic words it will go in.

I think it's easier off the bike, nothing is in your way, and you can push straight down much harder without knocking the bike off the centerstand. I don't even use a vice, just stand it on the ground and put the cap on. Marking the cap so you know where the thread will catch is a good idea.

[JTGS850GL]

Will let you guys know how it goes tomorrow.

[snackie]

Thanks everyone. I'll do it the right way, forks come off Sunday, weather permitting.
Turned out the instability up front was a flat REAR tire. Mind you it was my first time riding the bike since getting it running and the tire is BRAND NEW, so I was thinking anything but flat rear tire.

Thanks again!

[BigD_83]

Thanks everyone. I'll do it the right way, forks come off Sunday, weather permitting.
Turned out the instability up front was a flat REAR tire. Mind you it was my first time riding the bike since getting it running and the tire is BRAND NEW, so I was thinking anything but flat rear tire.

Thanks again!

Did you check and/or change the valve stem when you swapped out the tire?

[snackie]

Me and my buddy both spaced on valve stems. So, I tightened it and changed the core then checked for leaks. I'll just have to keep an eye on it.