Why does used fork oil smell like sewage?

[LuciferMutt]

I'm wearing a hazmat suit the next time I change fork oil...

[SikDMAX]

Originally Posted by wsmc831

You won't ever get all the contaminents out that are sitting on the bottom.

I had a neighbor for several years in San Jose by the name of Jim Lindeman. I talked to him several times about replacing fork oil. He argued very affectively that there is no way to get the proper amount of fork oil in each fork unless you remove the springs and let gravity and piston action drain as much as possible, then remove damper rod and compress forks with hand over open end to use air pressure for force in new fluid. He seemed to know what he was doing.

You bet your fork oil is in better condition than mine? It's not a competition. There is a right way and an easy way to do things. I can, and do, change fork oil in my bikes in about an hour, start to finish, and the experts say this is the correct way to do it. I will spend an hour every year at (least) to know my front suspension is fresh.

of course, I'm nobody to argue with bamboo and tape.

Bingo.

RIP Jim.

[wsmc831]

Yep, he was a good dude.

Another thing to think about with this method. Bike is sitting in the garage. While sitting, all contaminents settle to the bottom. Someone sucks up the top 80% (and that is very doubtful) of fluid, it's simply removing the BEST fluid, and replacing it with some slightly better. All crap is still at the bottom. Every fluid change I've ever done doesn't get rid of the junk until the last ounce or so, which tells me this does nothing but let crap accumulate over the years.

Not to mention taking out spring and changing/inspecting seals is a good time to look at all the internal parts.

[PeterW]

The crap sitting on the bottom is fine, it's settled and it's not going anywhere unless the bike is upside down and bouncing down the road (And if that case I'm not caring about the crap damping). Until that crud gets 'quite deep' it's better there than stirred through the mix by a half arsed attempt to get it out.
(And quite deep crud in the bottom is the same as smells like sewage, not arguing that a real clean there isn't needed).

Use protection (for the sliders ) and frequent oil partial changes are good enough. It's not a race bike where I'd be dicking with the damping to set it up for a particular track.

Not saying your method might not be 'better' but it's like changing engine oil more often than necessary. Yeah, in theory better, but in practice there more chance of making a mistake as well.

(Now where's that asbestos suit).

Pete

[cat]

That's just rationalisation, to avoid taking the forks off. :)

[Benesesso]

Forks should be disassembled the first time and cleaned well. After that, just drain and refill. Fork oil really has an easy life compared with engine/trans oils.

[concours]

I still want to fart in the face of the engineer(s) who decided we no longer needed drain plugs in forks. A heavily festooned 860 lb. cruiser is just a crazy waste of my time to REMOVE the fork tubes, rather than simply draining.

[Big-O]

Wow, I thought it smelled like sewerage cause I kept pouring liquid poop into my forks after eating pizza and drinking beer all night. Crap always ended up with that greazy sheen the next day, figured it had to have some good lube component to it.

[ragtoplvr]

I knew a machine operator that got a nasty infection machine coolant. He may have been immune comprised in some way, but there may be critters that live in oil that can hurt you. So wear gloves and be careful.

Rod

[PeterW]

Originally Posted by concours

I still want to fart in the face of the engineer(s) who decided we no longer needed drain plugs in forks. A heavily festooned 860 lb. cruiser is just a crazy waste of my time to REMOVE the fork tubes, rather than simply draining.

Amen. Even on lighter bikes it's a pain.

That's why I came up with the lazy bastards workaround in the first place.

Pete

[Zuber]

I do a lot of suspension work. Most people don't think of suspension maintenance until the seals leak.

All that black stuff is usually aluminum oxide, you know the active part on black sandpaper? Works the same. I've seen a lot of forks that have the slider worn out and no new bushings or seals will ever fix it. Buying suspension parts is very expensive. Seals, oil, not so much, but a slider can run into the hundreds.

The old damper rod forks could drain out most of the oil. The cartridge forks are impossible to drain without taking them down.

The 'friction modifier' added to limited slip rear ends is fish oil.
The smell from gear oil is sulfur.