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Discussion Starter #1
I to a suspension shop in San Jose last Saturday and their opinion was my forks are very slow to compress and rebound. He recommended changing the oil which I've been contemplating for awhile anyway.
What is the stock fork oil weight?
Do they come pre-filled from the factory or is it up to the dealer doing the setup as to what goes in there?
Thanks,
 

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I yam what I yam
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I've been reading a lot of old threads in preparation for suspension upgrades and it seems a lot of people replace the original fork oil with 5wt. This would "loosen up" your damping some.
 

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When I changed the fork oil in me ´04 ST3 I did use Motorex Racing Fork Oil 7,5. Next time I will use 10 or 15 as the forks are to soft now.
After 20k mile the old oil look like gray paint.
 

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Discussion Starter #5
Thanks! I'm looking forward to changing the paint out for new oil. Anyone heard of putting GSXR internals into and ST3 fork? i heard the other day the parts are interchangeable and are likely easier to find.
 

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When I changed the fork oil in me ´04 ST3 I did use Motorex Racing Fork Oil 7,5. Next time I will use 10 or 15 as the forks are to soft now.
It's worth checking (and possibly adjusting) your air gap (aka fluid volume, oil height, etc.). I'm not familiar with the ST3 specs, but most cartridge forks specify a range for fork oil volume. If your forks are toward the lower end of the range (meaning larger air gap, lower oil height), it will feel softer on compression, and more prone to diving under higher loads, hevy braking, and so on.

For damper rod forks, going to a heavier weight oil (or a lighter weight) is a common way to adjust damping on the cheap, but it is generally not advised for cartridge forks (because the shim stack controls damping more so than the oil weight, its not a single aperture like damper rod forks). With cartridge forks, heavier weight oil is more susceptible to viscosity changes as it heats up, the changes in viscosity translate directly to changes in damping. So the damping is weaker/softer when hot and firmer when cold. using a lighter weight, like 5 or 7 is more typical because the viscosity changes less throughout normal operating temps.
 
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