what weight/level of fork oil?

[davesta]

hey everyone, i'm thinking its prob time to change my fork oil as i've had my bike for over a year, havent changed it yet and am not sure when it was last done. I was told by the guy i bought it off (my boss at work) that it has race tech front emulators so i'm assuming it does (pretty straight down the line guy). Anyway i would weigh close to 100 kg by the time i'm all geared up and occasionally i take my girlfriend on the back who weighs about 50kg. Do you guys have any feedback on what thickness and volume of fork oil i should be using for my weight? Also, any other hints/tips i should be aware of when i'm changing the fork oil (i have a front stand and have downloaded the manual). Thanks heaps guys, really appreciated
dave

[neilb10000]

Hi Davesta,i don`t know about everyone else but i used a thicker viscosity oil than stated in the manuals,and slightly more of it.use a measuring jug and do one fork at a time.I suppose it`s personal choice really,but thicker/more oil seemed to give a nice feel to the front end.

[youngy]

measure the fork oil by level, not volume. stock level is 140mm down from the top, springs removed, for legs compressed.

[davesta]

I guess the thing that confused me is that i've seen some ppl elsewhere recommend a thinner oil for a heavier person, which doesnt make sense to me (but my knowledge of motorbike suspension is fairly limited). Would using a stock viscosity oil filled up higher in the fork make it firmer/better for heavy loads?

[youngy]

No. You would need to change springs. Less air gap will make the suspension more resistant to initial compression - too little air gap will make it very harsh. If you are suffering severe dive on the brakes you could try 130mm air gap, but if you go much less than that it tends to kick off bumps alot.

Is it Japanese spec bike or a euro/oz bike? Japanese home market bikes have much softer fork springs.

[davesta]

Its an oz spec bike, i honestly don't notice too much dive, though i'm probably not going as hard as some of you guys. When i look at the forks after a ride, though i can see that there has been a fair amount of travel, more then what i would expect. I do have goldspot front calipers with an r6mc and braided lines which would make any dive worse. I might go a slightly thicker oil and go for a 130mm air gap. Is there anything else that is commonly done at the same time as changing fork oil? I was gonna change the fork seals, cos they're almost 10 years old now, is there anything else? Thanks again for all your comments

[youngy]

If you're going down the route of seals (I wouldn't if they're not leaking) then you'll need to change the fork bushes too. You have to disassemble the forks to change the seals, so putting new bushes in is an extra 60 seconds work.

TBH you will find a huge improvement by just changing the old shitty oil that's in your forks for new fresh 10w oil at 140mm. Heavier oil may not be beneficial.

[davesta]

Actually, funny you should say that, i was just looking thru the manual, and while i think i could do it (disassemble forks), i wouldn't do it for the sake of it. The seals are fine, so i'll leave them. Only problem i have now is, the manual doesnt say how to just change the oil!

[youngy]

Remove the clip ons. Loosen the top yoke clamps, spindle pinchbolt and spindle and caliper bolts. Loosen the fork caps by a turn or two. Get the front end off the ground. Disconnect speedo cable at wheel. Remove calipers, spindle, wheel, mudguard. Undo bottom yoke clamps. Drop fork legs out. Remove fork caps carefully as there's a big spring under them! Remove the caps with rebound rods and springs, spacers etc.

Upturn the legs over a bowl and pump the old oil out. Keep pumping til there's no more then leave them to drain.

Compress the legs fully. Begin filling with oil. Pump the legs up and down to push out the air below the damper rods. Oil level is measured with the forks compressed. So you can use a steel rule and a torch or a turkey baster or syringe to get the oil to the correct level. Make sure you expel all the air. Put the damper rod and spring etc back in. The damper rod will only go in to the correct depth if it's in the centre hole - if it won't go in fully chances are it's in one of the damper holes.

Put it all back together. Forks pull through 18.5mm above the clip-on.

[phuk72]

If you can, leave the fok legs upside down overnight so that you get all of the old oil out.

If it's worth doing .........

[davesta]

Thats fantastic, thanks so much guys for all your help. I'm not the worst home mechanic in the world (no way near the best either!), but this is a big help. Cheers

ps and yeah i'll leave them overnight to drain properly
pps i knew that front headstock stand would come in handy

[bobtrx]

Davesta I would ask your boss if he had the springs changed , is he your weight , maybe put in a set of racetech springs to suit your weight , racetech has outlets in melb ( suspensions r us 5998 1021) and set your levels as youngy said . The springs set the amount of suspension travel the oil sets the speed of travel . look up sag settings to get the spring preload