SOHC.co.uk Forums > CB750

Forkin' ell

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Bristolbadger:

--- Quote from: K2-K6 on December 01, 2022, 10:18:33 AM ---That casting type was on the end of SOHC production (750 F2, CB650 I think) then on following twin cam bikes.

150ml not a bad start point if you can't find information as it's not absolutely critical.

Minimum has to still cover damper valves (with spring volume in the fork cavity ) such that it doesn't go into air and not damp. Maximum is more to do with air gap above the oil and going too high here will give hydraulic lock to prevent fork compression. 

This Maximum is usually considered adjustable in level if you want for example to give more air spring effect at full compression in preventing bottom out under heavy braking. Tweaks of 10ml going upward from 150 ml would be normal to assess.  Or measuring down from top of stanchion with a dipstick to set that way.

The 750 F2 manual states 145~155 cc fill volume.

--- End quote ---
Great stuff, just the info I was hoping for.
I was thinking F1 but the workshop manual wasn't definitive...
Mucho gratis!

andy120t:
Same as my CB650 ones too.

McCabe-Thiele (Ted):
Ok so use ATF but there are so many types of  Dexron grades upwards to  fully synthetics interesting -  when I put my forks back together I will be faced with so many options.

I'm minded to use what I have in stock Fuchs Titan 4400.

Opie oils is often my provider of choice - https://www.opieoils.co.uk/search.aspx?search=ATF

K2-K6:
I prefer to use Motul fork oil in any fork built now.

Nothing wrong with ATF but these formulated for forks only hold advantage in how they work and with reduced friction I feel.

ATF has a very tight tolerance and good product reputation for automatic gearboxes, but has to stay confined within very close technical performance for clutches etc, which fork oil doesn't need to comply with.

Principally ATF was used as it has high anti-foaming performance which is of value in preventing aeration when used in dampers. Very high wear resistance (spalling etc ) for gear faces that exists at very high torque loading on the gear sets. Although good it is outperformed in forks regarding stiction by good fork oils, this to help with giving a more silky smooth fork travel.

McCabe-Thiele (Ted):
What grade of Motul Fork Oil do you is it there seem to be in quite a bit few grades from 5W to 20W?

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