fork seals

[sae3231]

what is the best/easiest way to change the fork seals on a 77 gs750? I'm an auto mechanic but I'm new to motorcycle repair and the manual I have doesn't do a good job of describing the procedure.

[fastpakr]

Different people have different approaches. I just remove the forks completely and disassemble them on a workbench. Once they're apart (you'll need snap ring pliers and the right sized allan key at a minimum, some people have to rig a way of holding the damper rod in place to remove the allan bolt holding it in place), the old seal will just slide right off. To put the new one on, get a piece of pvc long enough to go all the way down the inner tube and tap the seal in place with a hammer. Use a narrow piece of pvc pipe inside to tap the fork back out of the tube you used as a driver. Sounds complicated, but the whole process of driving in the new seal and pulling the tube back off takes less than a minute.

[caberguy]

having just done this today on the same bike I have two first-timer pieces of advice (my first time too... I learned the hard way). 1) the hex screw at the bottom comes out much easier (well...comes out period) if the unit is under tension (i.e. top cap on, spring compressed). I sat there for 10-15 minutes just spinning the stupid thing and trying to figure out what was going on (the Haynes manual doesn't mention that you have to keep the damping rod from spinning...oh yeah), then put my new spring in, tightened the cap a bit and voila... okay, not quite voila... then I noticed that the inner tube was turning, at which point I grabbed a spring clamp, popped it on the tube and held it in place with my knee. This provided enough friction to push against for the hex bolt to come out easily. Then took top cap back off and spring out and disassembled. 2) as an Auto mechanic you might have one... but if not, get a seal puller (I picked one up at NAPA for $10). I probably spent an hour trying to pry, yank, cut and otherwise dislodge the freakin seal to no avail... got the right tool and it took 2 minutes... I think it was $10 well spent. The whole project (installing new Progressive fork springs, changing the seals, changing the oil) should have taken maybe an hour, but ended up taking more like four (I also couldn't find my metric hex wrenches... so that didn't help, got some for $1.88 at Big Lots...woo hoo)

[kiwijetpilot]

Lol well I just changed mine yesterday.

Got the allen bolts out fine, on my bike the damper rod doesn't seem to move when under tension (84 GS750ES).

But could I get the seals out? Nope. Sliding the outer fork tube down hard (like a slide hammer) didn't dislodge them. Must have tried that for an hour. In the end, I used enough force to turn the spacer (that sits under the seal, and should force it out) into a pretzel. The tube then popped out through the seal. However, the seals themselves hadn't moved, even though the forks were now apart... to cut a long story short, I had to virtually destroy the seals to get them out. Bear in mind I must have changed dozens of fork seals over the years.

Getting the new ones in was hard too. Despite sanding the sockets slightly to remove any small imperfections, and using some grease, they still took an hour each to get in... having to go gently to avoid distressing the top of the seal too much.

It was by far the hardest seal change job I have ever had to do... so good luck!

Simon

[Joe Nardy]

It sometimes helps to heat the top of the sliders with a heat gun or (very carefully) with a torch. This expands the slider slightly and the heat also helps break the seal between the fork seal and the tube.

Thanks,
Joe