ATF or Fork Oil? For 1983 Honda CB125

[ajordan9]

Hey all,

Recently noticed a bit of leakage from one of the front forks. So going to strip them, clean them and put them back together with new seals and oil. However when looking at the Haynes manual it says to use ATF in the forks. I just wanted to know if anyone thinks its a good idea of switching to 10W Fork Oil instead?

In all fairness as its an older bike so it could already have Fork Oil in there from a previous owner (I bought it earlier in the year) but I try not to assume anything.

Just thinking fork oil is specifically designed for the job it does and could perform better, where I assume ATF was all they had back in '83, although I know many still use it.

Let me know your thoughts.

[stinkwheel]

I would use and have used ATF, it is designed to take a real mechanical hammering over a variety of temperature conditions.

That said, I mostly use multi-grade fork oil now after having trouble losing damping effect on protracted, high-speed runs along bouncy roads. This was due to thinning of the damping oil due to excessive heat generation. The multigrade is less affected.

Of all places, halfords do a 5w-30 fork oil.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Snod Blatter]

For what it's worth, ATF is about equal to 7.5w fork oil. I'd probably go with whatever's cheaper, which I would expect to be the ATF..
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1994 CB250, 1984 CBX250RS-E, 1989 K100RS, 1995 TRX850, 2016 Z250SL

[Pigeon]

I use Fully Synthetic Dexron 6 ATF (30 cSt@40c and 6 @100c). 151 Viscosity Index.

I've also used 0w20 engine oil (46 cSt@40c and 8.6 @ 100c) 168 VI

Done about 10k miles on each for a bikes around 200kg with stiffer springs and rider who's 100kg.

The damping using 0w20 made the ride incredibly comfortable. But fast turns were harder work.
ATF is noticeably harsher (but not any worse than a similar weight/vi mineral fork oil), but bike is livelier on the change of direction.


A 120KG CB125. ATF would be perfect.


What do you get from proper suspension fluid / oil. Well, in my a-little-knowledge-is-a-dangerous-thing mind, when it comes to mineral oil. Not much. Apart from very smelly oil after just 12 months.

Mineral fork oil has a low VI. So it starts out thicker and ends up a lot thinner (read crashy).

I've used Castrol, Fuchs and Motul mineral (and synthetic) fork oils.

I don't think ATF is any worse than mineral (in terms of VI) and its half the price.


What does really expensive suspension fluid get you. Very high VI (200-500 compared to 120-160).
So it is much more consistent from the moment you set off, to 3 hours later. Is it worth the cost, up to you.

£05 1L Dexron 6 Fully Synthetic ATF (30 cSt@40c and 6 @100c) 151 VI
£05 1L Petronas 0w20 engine oil (46 cSt@40c and 8.6 @ 100c) 168 VI
£10 1L Mineral oil (Motul Expert 10w 36 cSt@40c and 6 @100c) 112 VI
£23 1L Silkolene 05 Synthetic (43 cSt@40c and 9.5 @100c) 212 VI

Somewhat annoyingly, the better example can no longer be bought.

£?? Silkolene PRO RSF 10wt (47 cSt@40c and 14 @100c) 303 VI

It looks like Silkolene no longer sell their ultra high VI fork oil.


Got carried away. ATF is fine

[A100man]

Look out Teff.. you've got a challenger..
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