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Discussion Starter · #1 ·
Trying to add new oil to my fork tubes on my '82 KZ750H. I bled the old oil from the bottom screws. The oil that came out was a messy gray color! I got the caps off and pulled the springs. Every part I took out was covered in a thin, gray sticky mess, almost like a light axle grease had been used. Frankly, I don't think in the 28 years of this bike's life, the forks have ever been serviced. There was no air in the forks when I tried to bleed that.

Anyway, as I do not have the tools to disassemble the tubes, is there any kind of flush or solvent I can run through them that won't hurt the rubber/plastic seals? Thanks!
 

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Polkat: I've done up about 20 bikes in my years and they have all had this mush in the forks. Seems nobody wants to do this simple service. You're spot on about the gease. There are commercial aluminum soap greases, and the oxidized oil in you fork eats the aluminum, forms this soap, the combines with the oil to make this in situ grease. I clean the parts with lots of dish soap and hot water, then a degreasing spay, then a solvent like paint thinner, and then a light oil. Don't sweat degradation of the rubber parts. This rubber will take a lot of chemicals if the contact time is short, like a day or two versus years. Get a 5W30 oil back in the forks quickly and make sure everything gets coated. Then of course, change the fork oil more frequently than the louts that sold us these bikes. Good luck.
 

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Eddie Lawson is God!
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I own almost that EXACT bike (80 KZ750H1) and the chance of having GOOD fork seals in it are NONE. I realize you want to save money (don't we ALL???)
But you should take your removed fork legs and bring them to a motorcycle shop. Have the forks disassembled, cleaned and the fork seals replaced. If it isn't a Kawasloppy shop, bring your new fork seals AND the fork oil amount with you. Fill with 15wt oil.
 

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Polkat: I think it is just Gunk Engine Degreaser. This is pretty good stuff as the oil and grease disolves in it, then when you hit it with hot water, it emulsifies in the water and cleans up quite well. Do wear some saftey glasses, as it is nasty stuff in the eye. I should have also said that sometimes you can beat a pressure washer for shifting crud.
 

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Discussion Starter · #8 ·
No, I don't have access to those tools.

A guy down the block from me just told me that he flushes his fork tubes (while still on the bike, a Harley) with about a cup of plain old gasoline. He leaves the bleeder screws in, lets it sit about 10 minutes, then drains it out and lets it dry for a day. Okay, of course there's a safety factor here, but does this work, and work without hurting the rubber parts?
 

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Gasoline is a hydrocarbon, just like the oil, so elastomer compatibility will be the same for both. The gasoline will be more aromatic and the oil paraffinic, but no harm for the short contact times. The best approach is stirping cleaning, and careful reassemlby, but the on-bike flush is better than nothing. But I'd flush repeatedly until the rinse is clean. Might take 5 flushes.
 

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Discussion Starter · #11 ·
Okay, that's it. I'm going to take the tubes apart and do it right. It was mentioned that I can use a broom handle to hold the damper rod while I loosen the bottom bolt, and also mentioned that there were other ways. Can someone tell me about that? Thanks!
 
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