'Faulty' Fork Seal Job on 1992 K75S from Dealer

Looking for some advice before I go back to the shop in the morning....

In November I bought my 1992 K75S.

I took it to the BMW Motorcycle dealer in Manhattan where they did oil change, flush brake fluid, flush coolant, flush transmission (i think) and most importantly: new fork seals.

A couple of days later, another different motorcycle mechanic looked at the bike and told me i needed new fork seals. i just wrote him off as being not credible since i have just paid $400+ to have them replaced.

Now another new mechanic, whom i trust a lot, told me again the fork seals are blown on the bike. this is less than 3 months and 400 miles from service date.

my question is:

what can go wrong with fork seals installation to cause this kind of problem? i.e. could there be some inherent problem with my bike that makes the fork seals problematic?

any advice on how to approach this with original mechanic?

That's odd. I think we need some other opinions here.

I'm not a BMW mechanic but I have my buddies K75S in my shop to replace the fork seals. He swears they were done last season at the BMW dealer, but, they are leaking.

After reading this, I wonder if I can do any better.

What do your eyes tell you? If they're leaking, tell the dealership about it. They will probably stand behind their work.

There are a lot of reasons for fork seals to leak: pitted tubes, seals damaged during installation, too much air pressure buildup, grit between seal and tube, etc. Just tell them they're leaking (if they are).

I completely agree with Anton
A Dealer is always a good place to take a leak.

Give the Dealer an Opportunity to Make it Right

I agree with Anton also. If they aren't aware of the problem they can't fix it. As far as things that can cause fork seals to fail, anything that can impact exposed fork tubes (bugs, dirt, gravel). Check out the surface for anything including dings. Gaiters can help protect the tubes and the seals. I put some on my '87 K75 and never had an issue in 70K.

Popped the fork seals tonight.

I found something a bit interesting tonight. I don't know if it's a big deal but it is different than the forks I've done before.

The seals get installed before the tubes according to the manual. You install the tubes, tighten the bolt at the bottom, install the springs then then install the "plug" at the top. Fill with oil, "Bob's your Uncle". The whole system is extended.

On others I have done, tubes go in first without the springs, install the seals, fill with oil, extend the tubes, install springs and then the "plug" at the top.

Lots of forks don't have the convenient fill bolt at the top of the "plug" like this BMW so you need to fill before complete assembly.

Couple things come to mind, "ripping" the seal on tube install or too much air pressure when they heat up and are working.

Just some thoughts about the OP's comments.

I had leaky seals on my K75 because I waxed he fork tube. The wax built up in the seal and allowed oil out. I saw it my self.

AntonLargiader said:

What do your eyes tell you? If they're leaking, tell the dealership about it. They will probably stand behind their work.

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My eyes tell me the seals are leaking but I am a novice to Motorcycles so I somewhat disregarded this evidence at first, since I just paid to have them fixed. I wasn't sure exactly how they should look, i thought perhaps a certain amount of oil on the tube was normal, but yeah, it looks like its leaking.

Meanwhile, I took it back to the dealer this morning and it is my impression they are going to fix it under warranty (the original work was done on 11/20/2013 and approx 400 miles ago, the guy says the work has 2 year warranty)

My biggest fear is that they will call me later this afternoon and say ' yeah the seals are leaking but it is because of XYZ and will cost $more to fix'

195709 said:

My biggest fear is that they will call me later this afternoon and say ' yeah the seals are leaking but it is because of XYZ and will cost $more to fix'

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If there are pits or scoring on the fork tubes this is a possibility. Do yourself a favor and have the shop install fork gaiters (boots) while putting it back together. The parts cost is a few bucks and the protection for the forks is more than well worth it.

The fork must be disassembled to install new seals so if there was tube pitting or another problem you should have heard about it the first time they did the work.

The problem with fork gaiters is that you probably won't be able to see if the forks are leaking.

If it's not too late, ask them to accurately measure the fork oil fluid that they remove during this repair so you can know if they're adding too much, which can cause the seals to fail.

timtyler said:

The problem with fork gaiters is that you probably won't be able to see if the forks are leaking.

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Sure you can. There is a small hole in the gaiter that allows air in and out as the gaiter contracts and expands; it will also allow fluids to leave the gaiter. If the hole is properly positioned (low and to the rear of the fork) the fork oil will find its way out. Sure did on my GSPD. It is not also not a difficult job to loosen the bottom of the gaiter to take a look-see in there every now and then.

timtyler said:

The problem with fork gaiters is that you probably won't be able to see if the forks are leaking.

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While it might not be immediately obvious, you can tell. If Kevin's answer isn't sufficient, it is very easy to periodically loosen a clamp and look.

In 1986 I bought a K75. The dealer replaced a fork seal at the 600 miles service. Soon the other one began leaking so the dealer replaced that seal too. I replaced both seals again at the 6,000 mile service and installed fork gaiters. The seals I installed at 6,000 miles were still in the bike, not leaking, when the bike was wrecked at 370,000 miles, eighteen years later.

So if periodically - say once a year - I have to loosen a couple of clamps, push up the boots and look for oil, the protection gained for the seals and the fork tubes is well worth it.

Fork seals on K75

Anyone got suggestions or part #'s on fork gaiters that fit or look at least OK on K75's. I can't remember if any K75's or K100/1100's models came stock with fork covers.
Charlie

I got mine from http://www.kbikeparts.com/#Front End

The fork tubes are 42mm - so any 42 mm fork gaiters (boots) will work fine. I use hose clamps top and bottom.

The bike really doesn't care if they are KawaYamaSusiHon or other brand. Try any good dirt bike supplier if your BMW dealer draws a blank. When I wanted some the BMW dealer parts guy knew exactly what I needed and went next door to the Yamaha shop to get them. Thanks, Mike!!

I use shock sox (www.shocksox.com) or whatever similar brand that I find locally. Easy to install, keeps the forks clean, can be washed if they become soiled and can be installed/uninstalled without dismantling the front fork. Since I started using them, even on fully faired bikes, I have not had any seal failures. On Annie's F650GS single cylinder, seal leaks were an annual affair until I stated using the shock sox.

You bet..
Years ago darn near every UJM had fork boots - that some thought ugly so some even came in colors other than black to try to improve appearance- but they do a great job of keeping grit, rock impacts, etc from damaging those seals and causing way premature failure.

If you ride in clean rural air on dry days most of the time- may not matter so much. But if you ride in traffic that kicks up grit, on wet days a bunch, where wind blows sand, on gravel and dusty roads sometimes- its a fair bet that protection for seals will extend their life. If you leave them exposed, at least clean/inspect seal area periodically.

Note also that most modern BMWs have no seal protection for anything- not the front or rear of the bike. There are a few partial exceptions- for example the RT's tube tops are screened by the fairing and its fender shields the rear shock fairly well- but most models have NADA protecting front or rear- hence the industry in everything from huggers and link protectors to boots, etc etc.

Its amusing that BMW uses excellent waterproof electrical connectors for pretty much everything on the bike (despite periodic switch problems) but eliminates the seal protection equivalents. Not sure whether its cost, design fetish or what..

Don't buy shocksox off their site- its not secure...

PGlaves said:

The fork tubes are 42mm - so any 42 mm fork gaiters (boots) will work fine. I use hose clamps top and bottom.

The bike really doesn't care if they are KawaYamaSusiHon or other brand. Try any good dirt bike supplier if your BMW dealer draws a blank. When I wanted some the BMW dealer parts guy knew exactly what I needed and went next door to the Yamaha shop to get them. Thanks, Mike!!

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I used to buy Rancho-brand pick-up truck shock gators at the local auto-parts store. They worked fine.

timtyler said:

The fork must be disassembled to install new seals so if there was tube pitting or another problem you should have heard about it the first time they did the work.

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I guess this was the root of my original question. thanks for the answer.

here's what happened since:

i took it to BMW the next morning. they looked at it, agreed the seals were leaking, and took the bike to re-do them. they have the bike a week and 'fix the seals', no charge or hassle to me at all.

i pick up the bike and by the time i get home i'm thinking, damn.. looks like they are still leaking. sure enough was only marginally better and still obviously leaking.

i take it back and they again agree to look at it, but when i'm there the tech who did the work, says ' i'm not gonna do it again unless we add more parts' he mentions some parts (spacers? and springs?, sorry i don't know) he said the parts wear out and eventually the clearances no longer seal. ( i asked why they wouldn't have noticed that the 1st 2 times they did it but felt rude to push for answer, i'm sure they were trying to save me money and acting in good faith. )

what the heck could go wrong on the forks? whats my worst case scenario? my bike has 28K miles on it, probably the bulk of it commuting to the city (which means it has ridden over really rough ****ty roads)

if i do need new springs, what is pros v. cons of 'progressive springs'?

i believe the bike was mostly leaning against a wall getting rusty for at least a year maybe 2 before i bought it. if that matters.

lastly, i did get one weekend of riding (which included my first ever taste of the twisties ;-) but the bad news is that i noticed when i was going downhill at speeds around 30mph the front of the bike was bouncing around like i was on a really bumpy road. once it started it seemed hard to get smooth. i didn't really notice this on the interstate up to bear mtn, or the other times i've ridden - mostly in the city. i noticed it most strongly going slightly downhill

could that just be a tire out of balance or is it possibly related to the forks deal? the front tire is brand new, mounted and balanced by the dealer who has it now.

its been at the dealer over a week i still haven't heard news from them.

thanks again for all the advice and wisdom.