Fork leaking after dropping the bike

Alberto

Alberto

Joined
Sep 4, 2019
Messages
422
Age
49
Location
Georgia
Bike
ST1100
Couple of weeks ago I dropped my ST because I forgot to remove brake rotor lock. Now I found out that left side of the fork is generously leaking. the "bang" was quite hard but I didn't find any visible damage, except that speedometer cable was torn off. Fork has been rebuilt last fall and I didn't see any leakage before. Thorough visual inspection didn't give any clue.

Can the impact of the lock to brake caliper cause a damage to a fork seal or to something else inside of a shock absorber?
 
It could be the fork is cracked where the brake caliper mounts, or it may be brake fluid you are seeing and not fork oil.

I doubt the fork seal would be damaged by the rotor lock, no should it cause any internal damage that would cause it to leak.

If it is fork oil that can only come from the upper lip (aka for seal) or a crack in the lower body.

Since the brake calpier would have taken the first impact when the lock fetched up before you dropped the bike, I'd look at those mounting points very closely.
 
My guess is that the leak was not caused by the motorcycle falling over, instead, it was caused by the sudden fore-aft impact on the fork seal when the front wheel abruptly stopped turning when the lock hit the brake caliper.

It's not that hard to replace a fork seal, there is a post here in the forum that explains how to do it on a ST 1300 - ST1300 Front Fork Overhaul. If your bike is a ST 1100, the process is similar.

You will need to remove the front wheel to replace the fork seal. When the wheel is off, carefully inspect the brake caliper to ensure that none of the sliding pins in it were bent by the sudden stop. It would also be prudent to take the fork tube to a machine shop and have it checked for straightness. Although it is not likely that the fork tube was bent (the seal was the part that suffered), you don't want to go to the trouble of reassembling everything with a new seal and then find out that the fork tube is bent.

Hope this helps,

Michael
 
Obo said:
If it is fork oil that can only come from the upper lip (aka for seal) or a crack in the lower body.
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It definitely leaks leaks from the upper part of the fork, where the seal is. Fork tube (piston?) is damn wet too.
I'll check everything in the lower part of the fork too.

CYYJ said:
Although it is not likely that the fork tube was bent
Click to expand...
thanks for explanations, Michael. Hope that fork tube is not bent, in that case I'd need to find replacement, don't know where to find it now(. It seems to me now that I need to repeat rebuild of the left side of the fork, replacing seals and bushings maybe?
 
Alberto said:
It seems to me now that I need to repeat rebuild of the left side of the fork, replacing seals and bushings maybe?
Click to expand...
I doubt that bushings would have been damaged, but it seems pretty clear that the fork seal has been damaged by the impact. I seem to recall that the fork seal has a tiny circular spring inside it that maintains the tension on the rubber seal against the sliding part of the fork. My guess is that this little spring probably got flattened or displaced by the impact of the fork tube against the upper (fixed) fork assembly when the wheel came to a sudden stop, and that is why you now have a leak. As I mentioned earlier, I kind of doubt that the subsequent tipover was the cause of any damage.

Michael
 
CYYJ said:
My guess is that the leak was not caused by the motorcycle falling over, instead, it was caused by the sudden fore-aft impact on the fork seal when the front wheel abruptly stopped turning when the lock hit the brake caliper.
Click to expand...
I'd agree... likely the impact has dinged the fork bottom, which is now oval...
I advocate against disk-locks over the risk of damages they cause... rotor, caliper, wheel, forks plus the aftermath when hitting the deck...
 
ST1100Y said:
I'd agree... likely the impact has dinged the fork bottom, which is now oval...
I advocate against disk-locks over the risk of damages they cause... rotor, caliper, wheel, forks plus the aftermath when hitting the deck...
Click to expand...
Stopped to use this damn lock after the accident. Hope there won't be any damage requiring replacing big parts of the fork. Happily, caliper and rotor look fine at least.

Better to buy some kind of alarm system to not get worried about motorcycle sitting on the street in the night.
 
If this event damaged the seal, I suspect the bushings may be damaged as well, since they keep the tubes centered with each other so the seal can work.
 
Alberto said:
Stopped to use this damn lock after the accident.
Click to expand...
I've observed folks going down with brand new motorcycles, right in front of the shop, in between the parallel parked cars, damaging bike and cars...
I'd seriously suggest a retractable tether with the red [REMOVE BEFORE FLIGHT!] key-chain/tag wrapped around the handlebar as reminder...
 
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Its hard to imagine damage to the bushings/seal to the extent of leaking, but if thats the case, I would imagine after you remove the wheel, you should be able to "rock" the lower slider back and forth and feel the play that a damaged bushing would exhibit. It will be interesting to see what you find in there.
 
ST1100Y said:
I'd agree... likely the impact has dinged the fork bottom, which is now oval...
I advocate against disk-locks over the risk of damages they cause... rotor, caliper, wheel, forks plus the aftermath when hitting the deck...
Click to expand...

One "safety idea" is a string that is attached to the lock on one end and to the handlebars on the other. Works as a reminder you have a disc lock on.
 
Alberto said:
Stopped to use this damn lock after the accident. Hope there won't be any damage requiring replacing big parts of the fork. Happily, caliper and rotor look fine at least.

Better to buy some kind of alarm system to not get worried about motorcycle sitting on the street in the night.
Click to expand...
If you lock the forks with the key, a thief would have to lift the bike anyway. A 725lb lift? I doubt it.
 
ST1100Y said:
I've observed folks going down with brand new motorcycles, right in front of the shop, in between the parallel parked cars, damaging bike and cars...
I'd seriously suggest a retractable tether with the red [REMOVE BEFORE FLIGHT!] key-chain/tag wrapped around the handlebar as reminder...
Click to expand...
I second this. I have only once forgotten my disc lock, which resulted in the valve being torn off, but I barely saved the bike from going down. I now have a very orange cable that wraps around my handlebar, so that I don't forget!
 
I decided to put this lock aside, until I buy this reminder cable. I saw this cable many times on other bikes bit was sure that I wouldn't so careless to forget remove lock before ride.
 
Alberto said:
I decided to put this lock aside, until I buy this reminder cable. I saw this cable many times on other bikes bit was sure that I wouldn't so careless to forget remove lock before ride.
Click to expand...
I've seen some just buy some bright yellow paracord and tie to the lock then just wrap around the handlebar. Heck, maybe paint the lock yellow.. You could also lock your handlebars all the time which might 'remind' you that you also need to take off the disc lock... But, odds are, after this trouble you've had you'll probably always check even when you don't install the lock.
 
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