Fork oil weight

[Rick65Cat]

When I went to the bike shop I'm dealing with, they only had straight weight oil on the shelf. 5W, 10W, 15W, 20W.
The GS1000 service manual on-line says the oil should be 10W20. (Mine is a `78 GS1000C)
Should I just put in 15W and call it a day?

[hampshirehog]

You can experiment with different rates but 15w seems to suit a lot of people. I experimented and ended up with 15w in all my GSs.

[almarconi]

I've got 15W in my GS, 15W is a good middle of the road choice.

[Steve]

As you can see, many find 15w to be a good choice. Some time ago, I read an article on how to set up suspension. It said that you should use the lightest weight oil that will do the job. The only way to compare is to change the oil and test it for yourself.

I know that my Wing is not a fair comparison, but it came from the previous owner (a good one, this time ) with Progressive springs in the front, along with the recommended 15w fork oil. I found that after about two hours of riding, my wrists were hurting. I traced it down to the 15w oil not being compliant enough to soak up the little ripples in the road, like expansion joints. I switched to 10w oil and have enjoyed all-day rides ever since.

None of my GS bikes have Progressive suspension (yet), but they all seem to do well with 10w oil.
I find that it gives a comfortable, supple ride, yet still damps the motion of the forks quite well.

.

[Rick65Cat]

I guess it depends on your riding style. Back when I owned a NEW GS1000 I rode it VERY agressivly and it handled perfectly (scratching pegs on both sides). I doubt at my age I'll ever ride like that again. I just want compliant suspension that will absorb those frost heaves and cracks in the pavement.

[Steve]

The nice thing is that all you have to do is try one. If it's not comfortable enough, drain it, put in the next weight.

It's only a few bucks for fresh oil.

.

[Nessism]

Thread drift alert....

Went to the local Cycle Gear and they want $15/quart for Bel Ray fork oil (choke, choke, cough, cough). They typically stock Maxima fork oil for $10 but were out of stock. WTF is which these prices??? How different is fork oil from regular motor oil anyway, and please don't say anti-foam additives since I'm pretty sure motor oil has that anyway.

Yes, I'm a cheap skate. Guilty as charged. That said, I spend tons of money on my bikes and do not typically cut corners...only I know when I'm being raped and I don't like it.

What's the equivalent to diesel oil in the fork oil world?

[Steve]

Evidently it's been a while since I bought fork oil.

The last time I got some was a couple of years ago, when we did the forks on #2 son's bike. Had enough left over to do "Freebie", so was unaware of any increase. I seem to remember $7 or 8 for the bottle.

Iron Pony has some Spectro fork oil for just under $10.

.

[Steve314159]

Simple question: you seem to be able to change the fork oil quite easily. To me, it looks like you have to completely disassemble the front forks to do that. I was thinking about draining and filling like I do on my boat lower unit; drain the old and then pump the new in with a hand pump. Is that possible or in general how do you guys do it? Thanks.

[Steve314159]

Oh, and I forgot, whatever happened to mixing motor oil and ATF? I thought I saw that in the manual but can't find it.

[Rick65Cat]

Simple question: you seem to be able to change the fork oil quite easily. To me, it looks like you have to completely disassemble the front forks to do that. I was thinking about draining and filling like I do on my boat lower unit; drain the old and then pump the new in with a hand pump. Is that possible or in general how do you guys do it? Thanks.

Yeah, I read that too. COMPLETE disassembly...I was hoping to just bleed the air, undo the bottom screw and let it drain. then hook up my bicycle pump to gently push air in to force the dregs of oil out.
Then add a pre-measured amount of oil via a syringe.

Probably over simplifying it

[Steve]

Simple question: you seem to be able to change the fork oil quite easily. To me, it looks like you have to completely disassemble the front forks to do that. I was thinking about draining and filling like I do on my boat lower unit; drain the old and then pump the new in with a hand pump. Is that possible or in general how do you guys do it? Thanks.

Depending on how recently the forks have been cleaned or had new seals installed, yes, you can simply drain and re-fill.

Oh, and I forgot, whatever happened to mixing motor oil and ATF? I thought I saw that in the manual but can't find it.

Back in the days when these bikes were built, mixing motor oil and ATF was the high-tech way to do it. Nowadays we have fluids that are specifically made for the job, and they are called "fork oil". Amazing, isn't it? Fork oil might have existed back then, but they figured that more people were likely to have motor oil and ATF sitting around, so they suggested mixing them for "proper" viscosity.

Yeah, I read that too. COMPLETE disassembly...I was hoping to just bleed the air, undo the bottom screw and let it drain. then hook up my bicycle pump to gently push air in to force the dregs of oil out.
Then add a pre-measured amount of oil via a syringe.

Probably over simplifying it

As I mentioned above, if your forks are relatively clean, go ahead and just drain and re-fill. Be as consistent as you can when you drain, to be sure that you get all the oil out that you can, then be as accurate as you can to get the same amount of oil in both legs. It won't be as precise as doing it correctly, but it's certainly better than nothing.

.

[Rick65Cat]

As I mentioned above, if your forks are relatively clean, go ahead and just drain and re-fill.

You be the judge

(Just pullin' yer leg bud)

[chef1366]

Nice bike
I'd say the forks are clean

[paco13]

definitely clean outside, but have they ever been apart?

If I remember right atf is about 11wt.
And I believe the hydraulic fluid for tractors and such is around 13wt. I had called and asked years ago.
Both cheap and local.
I tried them both on my old 550's. The Atf worked well. So did the hydraulic fluid, but it wasn't very plush over the small stuff.

Power steering fluid is another option that might be worth investigating.