72 CB500 Four Fork Oil?

[gioventures]

Alright so I'm rebuilding my forks for my 72 CB500 Four K0. I know that the manual says each fork takes 5.4oz (155cc) of SAE 10W-30 of oil per tube. If any one has any other unknown specs on that please feel free to mention it. What I'd like to know is, what kind of oil are you all using these days? Any brand in particular better over any others? Let me know what you're using on yours. Thanks/ ;D Also any website links to find these oils for good prices would be appreciated.

 

[dualitymike]

I just use regular ATF. Works fine.

 

[CarbsAndCylinders]

Most experts recommend fork oil over ATF these days. Fork oil is designed specifically for forks so should probably foam up less and also you can pick the best viscosity for you, your bike and how you ride.

 

[my-79-750-k]

Non-synthetic regular grade 10W-30. Doesn't matter which manufacturer you use, it's 99.9999999999999999999999999999999999999999999% the exact same oil, just in a different bottle, maybe with a couple extra molecules of detergent one way or the other.

 

[crazypj]

I use the cheapest full synthetic I can find in forks.
It is noticeably better than ordinary oil or ATF.
ATF was specified because it's available to a fixed standard all over the world
I use proper synthetic suspension fluid in shock re-builds though

 

[mark13018]

Oils are highly debated everywhere for everything... When you look for actual data and numbers it is hard to find non biased data due to someone trying to sell you theirs... I've tried to find numbers forever with no luck... I asked 3 of the local shops what they do and recommend and they all said they recommend atf as specified in the owners manual for vintage bikes and modern fork oils for modern bikes... Due to the lack of actual factual numbers by a 3rd party source and the level of experience in my local shops here, I do what they do as they each have about +/-60 yrs experience... I'm not going to spend extra money on snake oil but to each his own I guess though... Not many things more agonizing than debating oils.

 

[mydlyfkryzis]

I'll go way out on a limb and suggest you use SAE 10W-30 oil that the owners manual recommends.

That's the right starting point. Synthetic or dino, the viscosity is the same. Synthetic will not break down as fast.

If the bike is too stiff, or too soft, change the upper number, ie: Too stiff, try 10W-20 (or 5W-20)....If too soft, 10W-40 would do....

Not sure why everyone has a better option, as the damping on these bikes is crude, and what the book recommends prolly would work best anyway.

Most modern bikes have sophisticated damping valves, check valves. springs....The old bike basically have a rod running up and down in oil.....

I wouldn't over think it and stay with the manual.

 

[SONICJK]

The only thing you need to worry about is repeated cycling and frothing.
ATF is used in an environment where frothing is an issue, so its a good choice.
Engine oil is most likely just fine as well, thats what I use. All that matters, like mydlyf said, is the viscosity and anti frothing factors.
Any modern oil is going to be a step up from what the bike came with

 

[Rich Ard]

I use baby oil, and it's terrible. Don't do it.

 

[crazypj]

Yep, you have to squeeze a lot of babies to get a gallon ;D

 

[Scruffy]

How stiff do you want the forks. In my 1963 Honda I've tried atf, 10W30, 10W40, 15W40 and 20W50. I think it needs GL-1 85W, I despise front end dive under braking. If that doesn't do it, I'm filling the forks with concrete or making a micro springer/girder.

At which point my street legal TT bike will get a weld on hardtail, nothing, but nothing, feels as good to me as a rigid framed bike with a springer front end. No more brake dive, no more wallowing through corners, no more waiting for the suspension to let go under hard launches/stops...

Keep experimenting until you hit the right weight for how you ride. The factory recommendation is always the best starting point, go up or down in weights as your riding style dictates.

 

[gioventures]

Thanks guys! I def got a ton of info out of this and I'm going to do what most of you said. Just stick to the manual. Ill most likely just try the factory recommended SAE 10w-30 and start feeling it out on a few rides and maybe play around with the viscosity a bit depending on how I ride and how she performs. Ill post what I ended up using some time in the future.

Right now the bike is torn down to bare frame and I'm just in the fork rebuilding stage while all my other parts get powder coated. I might have to buy some tubes from Franks considering that one of the tubes has a bit of light pitting right under the "bottom out" line toward the top of the lower triple tree. I don't think any of my riding will have the leg spring hit the top area where the pits are and ruin the oil seal but I don't want to risk anything. I hope new tubes from Franks wont cost me too much.