Fork seal question - BMW F800 Riders Forum & Registry



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  1. #1
    flyrider's Avatar
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    My dealer is replacing both fork seals under warranty at my 6K service, as they are leaking. My question is...what routine maintenance do you do to keep leaks from occurring in your forks? I read on one old (2007) thread here that dead bugs should be cleaned off before they dry and become hard, because they can damage the seals. Really?

    What else might cause these seals to leak at only 6,000 miles?

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  3. #2
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    maybe all those stoppies and wheelies you've been doing testing windscreens
    '13 F800GT
    '93 DR350S 

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  5. #3
    flyrider's Avatar
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    Quote Originally Posted by Elizdad View Post
    maybe all those stoppies and wheelies you've been doing testing windscreens
    OK...that's one explanation I can eliminate!

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    My guess is they don’t so much damage the seals as they work their way under the lip of the seal & cause them to leak.
    This is a clear case of form over function(IMHO) as fork boots work so much better. But look less cool?
    As do longer front fenders.
    As always, YMMV
    07 F800 ST 

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    Keep your fork tubes clean, including free of bugs, and there’s a good chance you won’t have any more leaks. Or install some fork boots and don’t worry about it.
    2013 BMW F800GT | 2015 BMW R1200RT | 2014 Honda CB1100 DLX 

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  11. #6
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    I installed a set of wrap-around nylon fork boots (that seal with Velcro so that the forks do not have to be removed) and I also lube the chrome tubes with Tri-Flow oil once in a while. I never have had a fork seal problem. The Tri-Flow does a great job loosening any dirt on top of the seals where it gets deposited in a ring on the sliders, which can then just be wiped off after the forks have compressed a few times.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

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    the dust seals will keep most day to day crud out. So long as you're washing the bike regular you should be fine, more so if you live anywhere that has fine dust or sand that is more likely to find it's way into the seals.
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Spotlights, 50K Miles 

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    Any advantage in wiping down the fork tubes with some kind of oil, to remove debris? If so, what kind of oil? When I had my airplane, I always wiped down the front landing gear tube with brake fluid.

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    Quote Originally Posted by flyrider View Post
    Any advantage in wiping down the fork tubes with some kind of oil, to remove debris? If so, what kind of oil? When I had my airplane, I always wiped down the front landing gear tube with brake fluid.
    I recommend Tri-Flow. That stuff really works great to loosen dirt and to provide better lubrication than many other lubes like WD-40.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  16. #10
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    Quote Originally Posted by Richard230 View Post
    I recommend Tri-Flow. That stuff really works great to loosen dirt and to provide better lubrication than many other lubes like WD-40.
    Believe it or not, I read in a quilting forum regarding Triflow vs Sewing Machine Oil that "Triflow is basic mineral oil ( like sewing machine oil) added a bit of extra solvents and teflon......Triflow should make it extra smooth though, teflon in a good oil works well. "
    Sundog 

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    6000 miles seems unusual. Perhaps your F800 had defective seals from the factory. If there is damage on the fork tube(s) the dealer should catch it when he replaces the seals. Watch and wait.

    Dead bugs can definitely damage seals. When I rode to Alaska, I packed a cellulose sponge with 3M Scotch-brite on one side, keeping it in a ziploc bag. At the end of each day, I soaked the sponge in water, wiped down the fork tubes with the cellulose side to soften the goop, then flipped it over to scrub the tubes clean. Flip over again, and wipe the tubes squeaky clean, with a paper towel, if possible. After 11,000 miles, including several hundred on dirt roads, no leak. During the summer, I do this in the garage every 1000 miles or so, using isopropyl alcohol rather than water. Alcohol is a better solvent, and helps swell the seal rubber.

    Adding a small amount (~10%) of automatic transmission sealer to the fork oil also helps, but at 6000 miles, the seals simply should not be leaking. Suck out an equivalent amount of fork oil before adding the ATF transeal, to avoid reducing air space. If your forks dive a lot on braking, a small amount (no more than 10cc) can help reduce the dive, but too little air space can also lead to blown seals.

    I have used Gunk ATF Transeal on three different bikes, including a used BMW R1100RT, whose left seal started leaking fairly badly a few hundred miles after I bought it @ ~65,000 miles. The leak disappeared completely within a week or ten days. I sold it last month with 130,000 miles, still with the OEM seals from when it was manufactured in 1999. The leak never returned.
    Last edited by Selden; 1 Week Ago at 07:40 PM.

  18. #12
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    Must have been defective from factory. Since it's warrantied, no worries. The BMW tech who works on my bike does super work, so it ought to be "better than new" when I get it back early next week.

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    I brought my 2012 F800ST in for service and they told me my left seal was leaking (29k miles). They wanted $450 to replace both seals. I started looking online for solutions, and found Seal Mate. It was $5.49 on eBay. I gave it a try and it fixed the problem. Basically just a piece of plastic, cut specifically for the job. What happens is, dirt gets caught between the seal and the fork tube. This little gizmo pulls the dirt out. You then reseat the forks by pumping them a few times and you're good to go. Worked for me. No more oil on the forks, even 5k miles later. Worth a shot.

    By the way, people accomplished the same thing with other stuff, like 35MM film (what's that?). I just spent the 5 bucks, problem solved. Here's one of the videos I found.

    https://www.youtube.com/watch?v=p7u4Q9poAMQ

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    The Seal Mate is definitely worth a try, long term success rate is about 50/50, so totally worth it for how cheap they are. Plastic soda bottles work well too. That said, fork seals are a pretty easy job even for a home mechanic, it's only expensive for a shop to do it because of the time involved. Difficultly is marginally more than an oil change, though you will need a few new tools, but who doesn't like an excuse to buy new tools After you've done it a few times, the basic home mechanic should be able to knock out the job in about an hour per leg.

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    After I clean the forks, I apply RainX to the tubs, as the bugs don't stick so hard .
    Riding for the SON 

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    How has that worked long term? RainX lays down a physical layer that I would think might do more harm than good over time to the seals and bushings, not to mention that solid is dissolved in a mild acetone solution. I think the best way to keep the stanchions protected is a very light film of actual fork oil. A light smear with your finger and wipe the excess with a microfiber to leave a thin film. This is what I do for MTB forks and shocks that get ridden in harsh conditions to help the seals make it through a single season. I've not found a single other stanchion lube that doesn't trade off long term for short term. Even the teflon based specific lubes build up on the seal lips and cause stiction while holding debris over time.

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    Quote Originally Posted by rcb78 View Post
    How has that worked long term? RainX lays down a physical layer that I would think might do more harm than good over time to the seals and bushings, not to mention that solid is dissolved in a mild acetone solution. I think the best way to keep the stanchions protected is a very light film of actual fork oil. A light smear with your finger and wipe the excess with a microfiber to leave a thin film. This is what I do for MTB forks and shocks that get ridden in harsh conditions to help the seals make it through a single season. I've not found a single other stanchion lube that doesn't trade off long term for short term. Even the teflon based specific lubes build up on the seal lips and cause stiction while holding debris over time.
    it has worked just fine. on my F659gs I replaced the fork seals at 160,000 miles only because I put new bushing in. does not harm seals and makes the tubs very slick to reduce stiction.
    Riding for the SON 

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