USD Forks "Leak"?

Questions and comments about converting to beefier forks..
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Jeb
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USD Forks "Leak"?

Post by Jeb »

Having these USDs on my KDX marks the first time I've owned a bike with USDs . . .

so, should I expect to see a little oil leakage from these USD forks upon heavy usage? Like, any more than what you'd see with cartridge forks?

I've kept a close eye on them and haven't noticed anything that concerned me - until yesterday. 'Kiddo's on spring break, took the day off and took him to his favorite track. Dusty track. Once I figured out that I could keep my lame knee onboard and still have a little fun I beat 'em up a little bit (the forks!). Then I noticed for the first time a little oil from BOTH fork legs. Mixed with the dust it looked yucky. Enough oil for a tiny bit to sort of collect at the "seam" where the tube end at the bottom meets the ends that hold the axle - on BOTH fork legs.

They have also gotten a little softer like they've broken in.

I do vent them from time-to-time (a PITA, I need some of them handy-dandy push-to-vent devices you guys rave about).

Surely the fork seals last longer than this! I did install them myself and certainly don't find it inconceivable to have screwed something up, but in such a way that both fail at the same time?

OR - a little leakage is normal . . . ??
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Indawoods
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Post by Indawoods »

Well Jeb... mine haven't leaked at all yet. So something is amiss...

Did you replace the guides too?
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Post by Jeb »

^ Are the "guides" the bushings? If so, yes I've replaced them as well . . . replaced the seals, the dust wipers, and both bushings.

One thing worth mentioning. Last night after cleanup and again tonight, just to confirm, I can get on the bike and while steadying myself with my left hand and holding the front brake with my right I can work the forks fairly deep into their travel. And last night and again tonight, NO oil on the fork tubes. And I'm talking I pumped on those babies 30-40 times . . .
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Post by Indawoods »

Get you some Seal Savers... that may stop the contamination of dust past your seals... I think it is probably alright though....
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Post by Jeb »

>|<>QBB<
Indawoods wrote:Get you some Seal Savers... that may stop the contamination of dust past your seals... I think it is probably alright though....
I believe that's good advice, Inda . . .

Maybe the dust from yesterday and getting the forks deep into travel had a detrimental effect . . . but perhaps it was temporary (?) Time will tell. I went BACK down into the garage and drove those forks pretty deep into their travel a couple more dozen times. I can wipe my fingers on the tubes just below the dust wipers and I don't get that wet look but I can smell the oil on my finger.

Maybe some Seal Heal? I looked on your synadvantage webpage for some directions for use - is the stuff mixed with the fork oil?

BTW thanks
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Post by Indawoods »

Yep...at 20%.... One bottle will do both fork easy....
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Post by IdahoCharley »

Jeb - were you bottoming your forks on the track?

If you are routinely bottoming your forks 3-4 times each lap you may want to increase your oil level 5-10 cc per leg until your routinely bottoming the forks no more than once per lap.

When your bleeding your air from the forks you do have your bike on a stand or at least no weight on the front wheel - correct?
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Post by Jeb »

>|<>QBB<
IdahoCharley wrote:Jeb - were you bottoming your forks on the track?

If you are routinely bottoming your forks 3-4 times each lap you may want to increase your oil level 5-10 cc per leg until your routinely bottoming the forks no more than once per lap.

When your bleeding your air from the forks you do have your bike on a stand or at least no weight on the front wheel - correct?
Come to think of it. I had dropped my oil level down a second time only a few days before I went riding these past few times . . . I could feel the improvement when I was riding in the woods, especially through some creek rocks. BUT . . . I was getting FULL fork stroke/movement (and a some bottoming) at the track.

So, I likely need a higher oil level for the track. But I like the improved suppleness of the forks with the lower oil level. A good candidate for some subtanks, maybe?? That way, I keep the oil level higher and shut the subtank valves off when on the track, but open em' up some when I'm in the woods . . . sounds like my next DIY project!

OH - "bike on a stand or at least no weight on the front wheel" when bleeding the air . . . :shock: 'Guess I'm learning as I go! :oops:

Thanks, IC!! More great feedback from my KDXRider pals . . .
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Post by Green Hornet »

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Post by AZRickD »

When I had my USD forks sent into MX-Tech, they found a number of things that were problematic. First, one fork had the internals (like a plastic guide) that was installed in the wrong order and it smashed itself.

The other problem was that there were small dings on the fork tubes on one side. They speculated that these were tool (hammer) marks from installing the seals. MX-Tech "polished" these dings down so they wouldn't be sharp, but he said that it was likely that each dimple would carry a bit of fork oil underneath the seal. I told him that I was hoping for a six-month fork service schedule to be able to take care of it.

Sure enough, I have a very thin coat of oil on that fork that is enough to collect dust. Question is, how much oil am I losing and at what point will a lowered fork oil cause handling problems? Maybe I could take off the top and add a millimeter or so, as needed.

I guess I'll find out on my next service in September or October (or sooner).

BTW, when I picked up my bike, I noticed that the Seal Savers were removed (they are not the velcro kind and I'd have to unbolt things to reinstall).

He said that he doesn't like them (stiction) and they generally cause more harm than good, including making it more difficult to properly clean them.

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Post by skipro3 »

If you only notice the oil when using the forks in a full travel condition, you may have a slight imperfection in the fork tube. Every time the seals pass over this spot, a tiny bit of oil can escape. I would NOT worry about a tiny bit of oil. If your fork seals are bad, they will leak just sitting there parked for a week in the garage. Losing a little bit of oil isn't going to affect performance. Losing an amount that can be measured in your fork is NOT a little bit. Check fork oil level to see if you can measure the lost amount. Also, if you are bleeding air from your forks, then they are holding a pretty good seal. They are at least air tight anyways!! And finally, I've noticed some brands of oil exibit the tendancy to weep past seals more than other brands. Maybe the molicules are smaller? Using ATF instead of or mixed with your fork oil will cause the rubber seals to swell slightly and allow them to seal. It's an old trick many use to extend the life of worn seals.
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Post by Jeb »

Cleaning the fork seals with the Motion Pro Seal Mate seems to have stopped the leak pretty much all together (see recent posting I started). I added some Seal Savers. After a couple of pretty good rides . . .

- there's no more leaking thus far, and I've put things through some pretty good paces. And oh my, how wonderful it is to have the the USDs when those deep mudholes and pockets between roots suprise you.

- After washing the bike and allowing the Seal Savers to dry, I'm finding a bit of dried dirt at the last 1/8" - 1/4", but further up the Seal Savers as you peel them up it's clean.
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