Fork oil

[popwud]

Starting to put things back together on my 500/4 74.

New bearings in stearing head and struggled with the fork oil seals, easy when you know how.

But my question is what fork oil do I use, book says 10w30? surely a single grade would be used today.

Cheers.

[K2-K6]

Thought there was something on the forum about that being incorrectly stated in the manual but can't be sure, anyone else remember?

Usually most of them are about a straight 5 or 10 grade for std forks, too heavy and they just don't respond to road bumps but just shake the bike up and down.

[popwud]

Thanks for replying, I did have a look round and settling for Halfords Castrol ATF TQ D111.

Theres quite a few references to 10w30 fork oil, I wonder if thats what was in forks originally.

[Bryanj]

Originally Honda used engine oil, then TQF but today the best is to use proper fork oil at about 20w

[popwud]

Thanks Bryanj but 20W seems a bit heavy for a road bike.

[HondaFour]

I use ATF or AQF in my classics, but I don't do any scratching with them so the soft suspension suits me

[K2-K6]

From my experience in playing about with different grades, once you get above 20 then it seems you'd have to have a particular reason to go that way.

If you go higher with a standard fork and springs you just overwhelm the spring rate and the fork is reluctant to move and respond as it was designed.

10 always seems a good start point as with the oil in good condition you get a good idea of how it feels before forming more of an opinion for your own use, usually it's pretty good at this point.

You'd probably get a little more adjustability by varying the level to the top of the forks (changes the volume of the air space inside the fork) to give a small amount of increased support with higher level or a bit softer by going down in volume if you felt the need to move away from std at all.

[HondaFour]

 I think ATF is about 10 and I agree with K2-K6 that with 20 you would need modified fork internals. A while ago I had 20 in my 750K4 and it was very hard almost as if the forks had locked up a bit. Honda specifiy ATF for many old classics and its good for the seals but a good fork oil 10wt or at most 15wt would be a more expensive but a step better option.

I use atf because it works well with a good mix of softness and damping, its very cheap compared to bike fork oil and i cover just a thousand miles to fifteen hundred miles on my classic hondas every year

[popwud]

Thanks all.....got some fork oil from Halfords 10w.