Fork seal leak

I've heard that Aprilia's parent company Piaggio is an unbelievable pain when it come to dealer support, especially parts supply. (I was informed of this by my local Aprilia dealer.)
 
Regarding fork seal failures...what exactly happens when this occurs? Does the fork lose compression and gradually lower the front end? Or does it just lose all it's damping ability, etc?

I'm only curious about the consequences: If you're out on a ride, far from home, can you continue to ride the bike?
 
Jim, a bikes front end is held up by the springs, so it won't collapse. Loss of oil changes the damping on the bike, and a leaking fork seal generally makes a mess of the right fork leg. When the front end is compressed the oil is forced thru tiny holes in the damper rod, as the fork decompresses the oil is drained back thru the holes in the damper rod. I believe I am explaining that right. The spring and air inside the tube controls the compression and the amount of oil, the weight of the oil, and the size and number of holes in the damper rod control the damping.

I'm sure someone much smarter and an engineering background will be along to correct me shortly lol.

Here ya go, found this which may explain everything better than I did

http://racetech.com/HTML_FILES/DampingRodForks.HTML
 
Thread starter
The bigger concern for me was that it was leaking right onto the brake disc, which would have effectively cut my braking power in half (fortunately this is a dual-disc bike, my Shadow wouldn't have been so lucky...) Mostly I'm just glad I took the bike in to get that accessory removed, who knows when I would have noticed the leak. Very glad to have it back. It's scary to think that there are more powerful bikes out there than this one. 60 in 3.3 seconds is beyond enough for me!
 
Lol there are bikes out there so much more powerful than this it is almost inconceivable how someone can ride one not on a racetrack. Once they got over 125 horsepower they were effectively too powerful for me. There are some now approaching 200 horsepower. Street bikes. That is insane. Luckily they are all speed limited to only 186 mph :rolleyes:
 
The ferret_imp said:
Lol there are bikes out there so much more powerful than this it is almost inconceivable how someone can ride one not on a racetrack. Once they got over 125 horsepower they were effectively too powerful for me. There are some now approaching 200 horsepower. Street bikes. That is insane. Luckily they are all speed limited to only 186 mph :rolleyes:
Click to expand...
yeah, those old Busas that would go 192 were pure insanity. What a relief that it was brought down to 186.
 
Jim21680_imp said:
Regarding fork seal failures...what exactly happens when this occurs? Does the fork lose compression and gradually lower the front end? Or does it just lose all it's damping ability, etc?

I'm only curious about the consequences: If you're out on a ride, far from home, can you continue to ride the bike?
Click to expand...
In the vast majority of cases, seal leaks develop gradually. In those cases you can continue to ride, just make sure it's not leaking on the brake.

A few years ago I made a dumb mistake and installed some lower windshield supports too low on my cb750s fork legs. They were fine with just me on the bike, but when I loaded all my gear for a 3500 mile camping/road trip, the front suspension compressed way more than usual under heavy braking. About 500 mi. into the trip, the lower windshield clamps had punched right through the seals. Doh!

I finished the last 3K miles with leaking seals. Handling was still OK. When I finally got around to replacing the seals another thousand or so miles later, there was still 3/4 of the fork oil remaining.

The worst part about leaking seals is the mess.

Pipes covered with burnt fork oil
6eb75d4984c64853591971a4af841c5f.jpg


Lower fork covered with oil
ccb84cad2e32aaea645dcc15ebd98bf6.jpg


I even had fork oil on the fuel tank
6accf50118512db3d6f02129b22b852a.jpg


Here's what a pair of jeans looked like after a few days on the highway.
e3415761262a0ca9c5531fa9459854b7.jpg
 
Yuk

All my jeans looked like that when I rode my BSA 750 triple
 
Deanohh_imp said:
The ferret_imp said:
Lol there are bikes out there so much more powerful than this it is almost inconceivable how someone can ride one not on a racetrack. Once they got over 125 horsepower they were effectively too powerful for me. There are some now approaching 200 horsepower. Street bikes. That is insane. Luckily they are all speed limited to only 186 mph :rolleyes:
Click to expand...
yeah, those old Busas that would go 192 were pure insanity. What a relief that it was brought down to 186.
Click to expand...
yeah, those old Busas that would go 192 were pure insanity. What a relief that it was brought down to 186. Yes, we can all rest easy now.

Agree, 125 is about the limit for any sane street riding. Modern superbikes may claim more but the computer won't give it to you in the real world, except maybe in a straight line, to some limited degree.

These days you can buy far more motor than anyone can use, and the computer takes over when your skill runs out.

You hope.
 
I've not had any trouble with the fork seals on my CB1100 but I used to have a Honda Shadow 1100 that had a very similar set of struts. I found that on the Shadow occasionally a bit of dirt or the remains of a particularly crusty bug would find it's way done into the seal. I would just pop the dust cover and take a .010 feeler gauge and slide it down between the strut and the seal and move it around gradually pulling it upwards. That would usually clean the seal lip out well enough to get things back to normal. Put over 100,000 miles on that bike and only had to change the seals once.
 
Yep. Motion Pro sells a thin piece of plastic (called a fork seal cleaner) for under $5 that does the same thing. It seems well worth it if it's only a bug or piece of grit that's causing the seepage. Certainly cheaper and less time consuming than doing a full seal replacement.
 
Deanohh_imp said:
In the past I've seen a strip of camera negatives used for that. But I haven't seen camera film for 30 years.
Click to expand...
I think I might have one lying about somewhere if you want to make me an offer. :D
 
Deanohh_imp said:
In the past I've seen a strip of camera negatives used for that. But I haven't seen camera film for 30 years.
Click to expand...
That's actually what I started using on my Shadow until a piece broke off and stayed down in the strut. I found the feeler gauge was much more durable.
 
Mad Max_imp said:
Maybe a couple of fork gaiters could solve the problem.
:rolleyes:
Adding a bit of classic look too.
;)
Click to expand...
Unfortunately that adds a new set of problems. They have a tendency to trap moisture and create corrosion.
 
There's a lot mentioned on there about attending to the headers with wire wool, which I assume is what we call steel wool. I hope y'all are using stainless steel wool because, depending on how agressively it is rubbed, the regular stuff will leave tiny particles of steel imbedded in the surface which WILL rust and cause an ugly stain.
 
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