Fork oil leak

[93Bandit]

Howdy folks,

It's been a while since I logged on last. I got a new job and the 850 has been severely neglected this year. I've put a whopping 50 miles on it since January.

Anyways, it's been sitting in my garage on the center stand. I left town for a week and when I got back I noticed a wet spot under the fork on the garage floor. At first I thought it was my brakes because I made new lines and rebuilt the calipers and figured I didn't get something tight. Upon closer inspection I discovered it was oil leaking from the TOP of the bottom portion of the fork, where the rubber dust cover/seal is. Is it normal for a bike to start pushing fluid from that seal? Doesn't make sense to me how it could push fluid up and out that seal? I didn't think the oil level was that high?

 

[Rich82GS750TZ]

That is precisely where the fork seals reveal their leaks. Pop the dust cap up off the lower(outer) fork tube. There will be a puddle of fork oil on top of the seal. Or if you just hold the front brake and push the handle bars forward and let it rebound, the uppers will be wet. Time for a rebuild with new fork seals.
see part #5.
https://www.partshark.com/oemparts/a/suz/50d4020ef8700230d8b4e669/front-fork-model-d

 

[bccap]

There are some hacks you can try before you rip the fork apart and replace the seals ..... I've tried this method in the past and it has worked .... I didn't use a feeler gauge or the special cleaner device I just carved something from an old water bottle to slide up there and clean it. But the last device in the video looks like it would do a better job .....

 

[Rijko]

I have seen that before multiple times.

Like you, i do not understand how it is possible.
When in use, yes.
But after weeks of standing still ... ????????

 

[2BRacing]

............ Doesn't make sense to me how it could push fluid up and out that seal? I didn't think the oil level was that high?

If your forks have the air valves on top for air pressure to assist damping, the air pressure is forcing the oil past the seal even when the bike is standing still. Be careful not to have too much air pressure in the forks - pressure should only be 8 to 17 psi.

 

[rphillips]

I don't remember the thing about cleaning out the seals was done nor heard of, around here, back in the day. Great video, if it works GREAT, if it don't work you've lost appx 15 min. of your time.

 

[Rich82GS750TZ]

I've also read or heard of using a piece of 35mm film. (Remember the stuff we used to use to record our precious memories before smartphones), cut it hook-shaped and sweep it in, around and up around between the seal and the inner tube.
This video has the same idea using cell phone screen protector. Not my video. I've never tried this.

 

[rphillips]

Looks like any thin smooth piece of rigid plastic, ie. 2 liter coke bottle, and the added "little hook shape" to pull the crud up and out...Pro models all over Ebay appx. $10

 

[93Bandit]

Thanks for the ideas guys. I suppose I could try cleaning the seals, but I'm sure they're shot. The bike is 41yrs old and I seriously doubt any of the previous owners rebuilt the forks. But I'll see if cleaning makes a difference. If not, the day I've been dreading has finally arrived...

If your forks have the air valves on top for air pressure to assist damping, the air pressure is forcing the oil past the seal even when the bike is standing still. Be careful not to have too much air pressure in the forks - pressure should only be 8 to 17 psi.

I did consider air pressure pushing it out, but I'm still not sure how that works. Air would have to get under the fluid to push it up and out, how that happens I do not know. And yes, I added air last year and only put in 8psi I believe. I remember being on the low side of the spec.

 

[93Bandit]

For those who've rebuilt their forks, what timeframe am I looking at for this job? If you had all the parts and tools needed on hand ready to go, could it be done in a day? A weekend? I'm mechanically inclined, I've rebuilt many engines, work on cars/trucks/bikes but I've never rebuilt forks before.

 

[Rich82GS750TZ]

This first and only time I did it, I think it took the weekend. I'm pretty sure now, after having stripped this bike down numerous times including doing new fork seals and bushings once, I could do it in about 4 hours, from removing the axle bolt to torqueing it back down. Having the factory service manual is indispensable. Add more time if you're planning on wet-sanding and polishing the lowers. There is no better time.

 

[bwringer]

From roll-on to roll-off, definitely under two hours. But I've done a lot of these, and have the tools on hand. Air or battery impact and M8 impact-rated bit for the damper rod bolt, a damper rod tool, seal driver.

If the brake pads got oily, you'll need to replace them, and clean up the calipers and rotors very thoroughly.

For a newbie, plan on most of the day.

Protip: order and replace the copper washer under the damper rod bolt, and the wire clips holding the seals in at the top. You also really ought to order up, or at least have on hand, one or two new damper rod bolts because these are a very oddball fine thread, and if they're damaged (which is common) you'll have to special-order replacements.

This generic fork seal driver will work just fine:
https://www.rockymountainatvmc.com/parts/tusk-adjustable-fork-seal-driver-p

Or, use a piece of PVC and whack it with a rubber mallet to drive in the new seals.

The order of operations is important, so pay attention to the manual.

It's also worth considering replacing the teflon-coated bushings, if you can get them. These can be expensive, so most folks re-use them for a while if they're not completely worn out.

 

[rphillips]

First time doing it, figure in head scratching time, looking at manual time, looking for tools or something that will work time, and possibly asking another question, or two, here. First time, not near as quick as Rich who's done it once nor anywhere close to wringer who's done it a lot. With the good info. from above, you'll get there. If you get it buttoned back up within the same day, I'll give you a pat on the back next time I visit MI.

 

[Rijko]

Agree with Brian, if you have the tools it can be done in approx. 2 hours.

When i do not have the right seal driver i use the old oil seal on top of the new one
so i can tap the oil seal in without fear of damaging the new one.

I usually rub the brake pads on a piece of sanding paper if there's enough meat on them.
Takes care of glazed surfaces and/or oil saturated top layer.

 

[93Bandit]

Cool. So I'll plan on a weekend. I will definitely order the extra parts mentioned, just in case. I'm not afraid of have spare parts on the shelf if they don't get used.

It'll probably take me 2hrs to take all the crap Ive mounted on the handlebars off before even getting to the good stuff :lol:

As always, thank you gentlemen!

 

[93Bandit]

Another 16 months have gone by and my bike is still sitting. I'm determined to get this done this winter, starting next month.

I need help identifying all the parts I'll need to replace. I want to be thorough and replace all wear parts so i only have to do this once. I want to install new springs to eliminate the air shocks but I'm not sure what to get. Any guidance on that?

Obviously all seals, but when I look at the parts list linked above, a few are unavailable. Does anyone have a PN cross reference that identifies other sources for those parts?

Also, i need to replace the head/stem bearings. They're severely flat spotted, but not sure what all i need to replace for those?

Would really appreciate compiling a parts list so I can order them asap so I can have everything i need to get it done next month.

As always, thank you!

 

[Rich82GS750TZ]

For the forks, I would start by identifying your particular bike year/model for the wear parts you need (seals/orings, etc.) on a site like partshark.com. Buy from them or at least identify the part numbers if NLA so you can look on E-bay or elsewhere. You want to use OEM/NOS whenever possible. If you're going to replace the springs with straight-rate springs, like Sonic, and a spacer, you may want to seek the guidance of RichDesmond, former owner of the company. Super smart with this stuff, and I know he's helped others get what they need.

Sorry, no help on the stem bearings. That's one job I haven't had to to (yet?). But I look forward to seeing how it goes with you.

 

[dandypop]

I performed a full disassembly and rebuild, and I'd recommend planning for a full Saturday for your first time (and if you don't need any parts that you can't get locally). I think 2-4 hours is realistic to just do the seals, once you know what you're doing. I must have damaged the seal when I put it back because it's leaking again. Or maybe I have a dinged-up fork tube, but I can't see any issues. Gonna try the plastic scooper doodad next.