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Discussion Starter #21
How about a quote from Dave Moss:

"Modern suspension uses very light oils. A change in viscosity by just a couple of points makes a big difference in suspension compliance and action. All that applies to the fork also pertains to the shock (or shocks). The piston wears on the shock body, picking up metal that then travels through the oil and damping circuit. If the metal chips are large enough, they can cut through seals; even at best, they act like sandpaper to damage the seals over time.

So what’s a reasonable interval? For sportbikes, simple replacement of fuids and seals at 10,000 miles will bring new life to the bike. Touring bikes and cruisers can probably double that interval before the service will offer noticeable improvements. But whatever the interval, it’s certainly not “never.”

Read more: Oil-Change Intervals For Your Suspension? | Street Savvy - Motorcyclist Magazine

Note that he writes about a modern suspension for thin fork oils, not a 70s style cruiser suspension designed in 1987 that would basically be garbage on a race track and is quite terrible on the street as well, from its low price and almost total lack of design.
 

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WOW! Jeff gets a bit wordy...Forken oil! Yea, I think fork oil intended for forks is a pretty sound idea. I generally put engine oil in my , wait, here it comes, ENGINE> Oh, and a little on my sidestand cause I can't find "sidestand oil". But Jeff, keep up the good work in your creative writing class and settle for Fork oil in the forks.
 

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Discussion Starter #23
"Use whatever feels right. I was just a little surprised that we are using anything from 10w to 50w in the same forks and everyone is pleased with their choice. Obviously you can alter the damping with a change in viscosity.

Apparently the forks are not real sensitive to viscosity changes, probably due to the fairly primitive valving. As I've said, even a 5 w change in my Ducati or Harley would be an extreme change.

When I started riding Triumphs it was common to use ATF in forks, it worked fine, it's cheap, and I always have it on hand. Of course, when I started riding Triumphs we had to watch out for Dinosaurs crossing the road."

from:

hydraulic oil for front forks - Triumph Forum: Triumph Rat Motorcycle Forums
 

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That Fighter Guy
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I think one of the fork seals started to leak at about 2,000 miles because the cheap-ass original fork oil was good at letting dirt get into the fork seals. Cleaning the original fork seal fixed the leak.
I don't know how I missed this before. This is proof positive that you have no clue how things work. You think fork oil allows dirt into the seal? You obviously don't know how a fork is put together. The oil seal keeps the OIL SEALED inside the forks. The DUST seal keeps DUST/dirt from getting to the oil seal and interfering with the sealing surface against the chrome tube. The dust seal isn't perfect and can allow dirt to pass and foul the sealing of the oil seal, causing a small amount of oil to leak past the seal. If you catch it early, you can easily clean the seal (Seal Mate by Motion Pro, film negative, thin plastic) to remove the obstruction. If the leak has been going on for some time AND cleaning the seal stops the leak, it's a good idea to change the oil because the leak will cause the oil to get contaminated over time. Contaminated oil will cause excess wear on the bushings and, in turn, require those to be replaced, which requires the forks to be completely dismantled.

Btw you're welcome for the free lesson. Let me know if I can clear up anything else for you. Knowledge is power.
 
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