FORK Oil!

[Jfishsolevibe]

Alright, so Mike's post on OIL is developing nicely - - What do you guys replace the old stuff with in the forks of your bikes?

Planning on rebuilding mine this weekend so this will be helpful information!

 

[domer]

the forks on my cb500 had "atf" stamped on them (before they got polished) appears to be filled with atf too. although ive never f'd with it!!! ;D

 

[hillsy]

I replace fork oil with..........wait for it...........fork oil ;D

Seriously, you only need to buy a litre - it's pretty cheap

As for weight? My "new" zx9 runs 5 weight, but for older forks you'd use 15 or 20 weight.

 

[Big R]

Actually it should be in the manual. I'm thinking it's something like 15 weight originally but I think some guys put in a mixture of 15 and 20 to help with brake dive

 

[vaca350]

I know the manual for my cb350 calls for atf but I think that it was printed before there was such as fork oil. I plan on putting some 20 wt in when I rebuild them. I don't see there being a problem as long as I flush them before I fill them.

 

[Rocan]

i run 15 weight. Seeing as how my 350 is pretty light, and im pretty light myelf at 145.

 

[crazypj]

We're mostly using damper rod forks which have no valving, just a couple of holes for oil to flow through.
Because of this, they only work 'properly' at a specific rate of movement (how quick they compress or extend)
Hitting a 20ft long 4"high undulation at 40mph doesnt feel as bad as hitting a 1/4" high raised white line or expansion joint at same speed because fork compression/movement is 'slower' in first case even though its moving much graeter distance
If forks are diving too much you probably need stiffer springs, then thicker oil 'may' work properly.
Personally, I'm having great luck with 5w/40 full synthetic multigrade motor oil, thinner than stock (which is usually around 10wt)
Changing to thicker oil may help prevent brake dive but only because the forks in effect, hydraulic lock during rapid movement. This means they can (and do)'hydraulic' during normal operation if you hit any sort of bump. (known as 'packing down')
It happens when forks can't extend before next bump comes along.
using 20wt oil with stock springs is generally a real bad idea unless your doing mods to damper rods for a specific fork acceleration. Except for the cost, emulators are the best modification you can make (but I don't think they are available for forks smaller than 35mm dia?)

PJ