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Author Topic: Fork piston seized to fork tube  (Read 1353 times)

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Offline Scotty J

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Fork piston seized to fork tube
« on: January 23, 2012, 01:31:33 PM »
I'm currently giving the entire front end the what-for (progressive springs, roller bearings in the neck, and lots of polishing), and one of my fork legs has a stuck piston.  The bike's a K2, but I'm pretty sure it's running an earlier model fork (I'm the third owner).  Mine looks nothing like the one in the parts manual.  Anyhow, for purposes of identification, from the bottom of the fork tube up, there is 1) a circlip, 2) the piston, 3) a skinny little ring, 4) another circlip.  You following me?  Hope so.  So I removed the circlip on one tube& the piston slid right off, but on the other tube the piston wouldn't budge.  I hit it with WD-40, then with liquid wrench, but nothing.  Is this going to affect fork performance at all?  I assume that it really only needs to be removed if it needs to be replaced due to a shrinking outer diameter.
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Offline Hush

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Re: Fork piston seized to fork tube
« Reply #1 on: January 23, 2012, 01:42:23 PM »
Might as well fix it while you have it all out, also since the other one was free then this one should match it in movement.
I don't second guess two things, brakes and forks!
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Offline Scotty J

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Fork piston seized to fork tube
« Reply #2 on: March 03, 2012, 09:05:30 AM »
Resolution:  I guess it's just a tight fit.  I pulled both circlips off and managed to extract the piston.  From what it looks like, the piston is removable as a durable part so you won't have to replace the entire fork tube if you're out of tolerance.  Anyhow, there was no rust or anything so I just cleaned it all up and reassembled.  I just picked up some 10w and my forks will be forks once again this afternoon.

New question:  anybody have an accurate volume measurement for oil when rebuilding a 71 fork with progressive springs?  The info from progressive said that their springs displace more oil, and measuring depth looks like a hit or miss endeavor.
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Offline MCRider

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Re: Fork piston seized to fork tube
« Reply #3 on: March 03, 2012, 09:14:54 AM »
Quote from: Scotty J on March 03, 2012, 09:05:30 AM
Resolution:  I guess it's just a tight fit.  I pulled both circlips off and managed to extract the piston.  From what it looks like, the piston is removable as a durable part so you won't have to replace the entire fork tube if you're out of tolerance.  Anyhow, there was no rust or anything so I just cleaned it all up and reassembled.  I just picked up some 10w and my forks will be forks once again this afternoon.

New question:  anybody have an accurate volume measurement for oil when rebuilding a 71 fork with progressive springs?  The info from progressive said that their springs displace more oil, and measuring depth looks like a hit or miss endeavor.
Besides using a baby bottle or RatioRite measuring device, measuring the level is the preferred method of fork builders. Tubes must be off bike, assembled but without springs. Tubes into legs full amount.  Chuck up vertically, held by lower leg, in a vice is good. Pour measured amount in one tube. pump it a little to get it in all the hiding places. measure the level down from the collapsed tube to the oil level. Fill the other tube up to that level.

Seems a lot of todo. I just use the measuring device for both. Fill it to the medium amt prescribed in your manual and run it. 220cc comes to mind.
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Offline southendfire

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Re: Fork piston seized to fork tube
« Reply #4 on: March 17, 2015, 04:50:14 PM »
I see this thread is a few years old, but hoping you might still respond. I've run into the very same problem on my CB450 K3. I'm wondering what your solution was? You noted that you were able to remove it. Is there anything more you can tell me about how it came off? Thanks.
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