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Cured-Leaking Fork Seals on 81 GPZ1100 forever --Cool "Trick" 23 Jul 2021 17:50 #852394

  • 577nitro
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I'm letting everybody in on a cool trick I discovered on stopping the constant leaking forks on the old bikes...and probably all others too.

The question, why do the start leaking?  Answer DIRT and Crud getting underneath the fork seal and lifting it from the tube surface breaking the seal.  Stop the
dirt and crud from getting there in the first place and they won't leak.   How to do this?  Shields and boots sorta work but eventually bugs and crap get under it.

"Dust" shield does nothing, so that's useless. 

So after pondering this due to the fact my forks would only last a week after the seal being cleaned (using this slick tool I made from a plastic milk jug).  One day notice that when I moved the zip ties I use for fork travel up to clean the seals it scrapped the bugs and crap off the tubes.  Huummmm???  What if I could make them move up and down with the fork lowers, then it would scrap them as I road never allowing dirt and bugs to contaminate the seals.  Epiphany sound here!

So I realized could put a small zip tie under the worthless (now worth something) dust cover/boot and the zip tie now slides up and down with the fork every stroke..ahead of the seal, scrapping the crud off the fork before it can contaminated the seal.

Results...over 6000 miles and two summers of bugs and rain and not one drop of oil since.   And these are the ORIGINAL 40 year old seals!  They leaked like a sieve when I got the bike, always leaked, and I read that they leak even from new...probably because of the looser tolerance on the older tubes (not really 38mm, more like 37.01234).  So it was easier for crud and bugs to get under the seals.  I've noticed zero ill effects, it slides up and down with near zero effort and no  scratches or streaks.  I swap the zip tie out every 2500 miles or so and also noticed the fork oil it is MUCH cleaner. 

Logical question, does it build up under the dust cover instead?  Nope.  Haven't seen a drop, nor do the bugs build up either, they never get a chance to dry and stick on..so they just blow off.  

What do I need to do? First clean the seal if its leaking, it doesn't fix a already leaking seal, it's a preventative measure.  You can make a tool to do this from a old plastic milk jug.   See attached photo, the X-mass stocking looking plastic piece on the fender is what I made.  Just cut it out of the thin part of the plastic, then slide it between the tube and oil seal (you need to take the dust boot off first) and scrap the crap from under the seal.  Keep doing this until there is no more dark crap coming out, clean all the oil and dirt off the fork tube.  Pump the forks to reseal.  You might want to change the fork oil at this point too of the seals are much contaminated..but don't replace then yet.  Now lift the dust cover up high on the tube and install a small zip tie (any brand you have should work) around the tube just above the top of the tube make it tight enough that it makes full contact with metal all of the way round.  Push it down tight against the top and reinstall the dust cover.  Your done!  If does for some reason cause a problem, which I have never seen, just cut it off.

Ride and check to make sure it is staying under the cover, as long as the cover is in good shape it should be fine.  You'll notice your fork tubes will ALWAYS be clean!  NO BUGS and no more leaks.   To re-iterate, my forks leaked from day one that I bought this bike 6 years ago, since discovering this they have not leaked since (6000 miles riding) on the original 40 year old seals.  It worked on my 85 RZ350, 97 CBR600F3 and ZRX1100.   I also have done this on my KDX200 dirt bike.

This is not going to make the seal makers happy...nor the shops for so many unneeded seal replacements.   I have some other ideas in the works for forks to help the seals last longer and reduce friction/stickiness.  

Thanks
577Nitro- JES

 
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Cured-Leaking Fork Seals on 81 GPZ1100 forever --Cool "Trick" 24 Jul 2021 06:51 #852421

  • martin_csr
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FWIW. New dust shields will probably block the crud.  When rebuilding the forks, I did a drop test to compare the new dust shields to the old ones.  The fork tubes dropped more slowly w the new shields installed, indicating that new ones fit tighter than the old old old ones.  The test is just something I came up with at the time.
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Cured-Leaking Fork Seals on 81 GPZ1100 forever --Cool "Trick" 24 Jul 2021 11:00 #852447

  • 577nitro
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Yeah, I tried that they may stop some dust, but dried on bug protien,  and oil/fat just smears.  This then just starts collecting grit and dirt, eventually the seals will start leaking again.  But it is a good thing to do anyway if they are broken down or damaged for sure.

Newer bikes definitely have far better seal protection..but eventually they will contaminate.

Remember my gpz1100 probably has the worst seals and protection, they are ancient, this stopped the leaking completely.  Any small amount of material on the forks starts the leaks. 

Thanks for the suggestion.

577nitro 

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Cured-Leaking Fork Seals on 81 GPZ1100 forever --Cool "Trick" 25 Jul 2021 06:18 #852500

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Forgot to mention, your idea is cheaper.  cheap is good. 

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