View Full Version : Correct oil for GSXR front end?
Can anyone recommend or tell me what fork oil they use in their GSXR front ends on an SV650?? Its a K4 racebike running K4 GSXR 1000 forks.
Thanks,Tommy
fastdruid
14-03-10, 09:51 PM
I previously believed that USD forks should be about 5wt but it seems weight isn't good for measuring fork oil and the different oils are all measured slightly differently...
http://www.peterverdonedesigns.com/lowspeed.htm
I'd suggest going with a make and sticking with it or going with the original Suzuki Oil. Failing that the Öhlins Front Fork Fluid (No.5, #1305-01) seems to be about the right cSt.
Druid
I'd suggest going with a make and sticking with it or going with the original Suzuki Oil. Failing that the Öhlins Front Fork Fluid (No.5, #1305-01) seems to be about the right cSt.
Druid
Has anyone actually used a different weight of oil seeing as the front forks are now supporting a V-Twin instead of a heavier inline 4??? Fork oil aint my forte :confused:
fastdruid
14-03-10, 09:59 PM
Weight of bike has nothing to do with weight of oil! :)
You want to change springs to match the bike (and the use) then tbh which oil is to a certain amount up to experimentation, from that link "Use the least viscous oil possible that produces good slow speed damping performance with the damping adjustment screws out 1 full turn from full closed."
If you want to copy someone else then just going by weight is no use, you need to use exactly the same make of oil too.
Druid
You want to change springs to match the bike (and the use) then tbh which oil is to a certain amount up to experimentation
Im doing this on a shoestring mate so springs wont be getting replaced this season anyway unless I win the Lotto :D Im opening the forks up to machine back my preload spacers so I decided I may aswell change the oil while Im at it. Static sag is to be set at 25mm but I cant achieve this even with the preload backed off fully so im gonna have it in such a way that when I have 25mm static sag ill be in the middle of my preload adjustment. Make sense :confused:
fastdruid
14-03-10, 10:18 PM
Hmmm, you really want to get the right springs but K4 I believe should be 0.85Kg/mm which *should* be about right, if anything a touch soft so you are going the right way about it by reducing the preload.
Put your actual weight into this
http://old.racetech.com/evalving/SpringRateCalculation/dirtspring.asp?brand=Suzuki&yr=03-07&ml=SV650S&formuse=form1&SpringType=Fork
And it'll tell you what it should be. I tried it with 80Kg and it suggested 0.9Kg/mm which isn't a million miles away from what you have.
I'd suggest you go with Suzuki fork oil to start with.
Druid
Hmmm, you really want to get the right springs but K4 I believe should be 0.85Kg/mm which *should* be about right, if anything a touch soft so you are going the right way about it by reducing the preload.
Put your actual weight into this
http://old.racetech.com/evalving/SpringRateCalculation/dirtspring.asp?brand=Suzuki&yr=03-07&ml=SV650S&formuse=form1&SpringType=Fork
And it'll tell you what it should be. I tried it with 80Kg and it suggested 0.9Kg/mm which isn't a million miles away from what you have.
I'd suggest you go with Suzuki fork oil to start with.
Druid
Recommended Fork Spring Rate for Racing: 1.038 kg/mm (use closest available)
Stock Fork Spring Rate: .850 kg/mm (stock)
Not a million miles away either so Ill carry on as Im going and change the oil. Im sure Ive a few gallons of Rock Oil racing fork oil somewhere.I won it at a raffle at the Manx GP in 07 :cool: Ill check what WT it is
fastdruid
14-03-10, 10:29 PM
Hmmm, how did you get a different "stock fork spring rate"? I got the SV as being 0.67
Did you run it for the GSX-R1000K4 rather than the SV650?
Druid
Did you run it for the GSX-R1000K4 rather than the SV650?
Druid
I did.
fastdruid
14-03-10, 10:38 PM
You want to run it for the SV, the fork spring rates are relative to the bike not the forks.
Druid
Weight of bike has nothing to do with weight of oil! :)
You want to run it for the SV, the fork spring rates are relative to the bike not the forks
You have me all confused dude :confused: Ill sleep on it and get back to it tomorrow
fastdruid
14-03-10, 10:49 PM
OK, oil weight is used to change damping rates. Standard damping GSXR1000 probably isn't far off.
Fork springs hold up the bike, springs are *bike* specific or to be more precise are bike weight, purpose and front/rear balance.
So although you may have GSX-R1000K4 forks they are fitted to a SV650 and so you need forks springs rated for the SV650's weight/use/balance *NOT* the GSX-R1000K4.
Hope that makes more sense.
Druid
yorkie_chris
14-03-10, 10:50 PM
Silkolene pro RSF 5 is what I have in at the moment.
Generally you want to look around 5w or 7w on the bottle, between 25-30cSt@40deg on this table:
http://www.peterverdonedesigns.com/images/content/motorcycle/PVD-ISO-Viscosity-Data.gif
When you are selecting fork springs you want to look at what loads the forks will have on them, so run the calculator for the SV.
Obviously if you just want to know what spring rate IS in forks you have then look at the spec for GSXR :)
OK, oil weight is used to change damping rates. Standard damping GSXR1000 probably isn't far off.
Druid
Valving is for change in damping. You want to use same oil all the time in gsxr forks and tune damping with valving.
Red Herring
15-03-10, 07:37 AM
I think all this talk about spring rates is very useful, but a little confusing. To answer the Op's original question if you are unhappy about the current range/performance of your damping then you need to consider changing fork oil brand and not just oil weight, but to do it properly you need to play around with the springs, the oil and the fork valving.
For my "GSXR-600/750" K4-K5 front end on pointy, with 10Nm Ohlins springs, the mechanic told me to buy 5w :?
Hope this helps :rolleyes:
I machined 5mm from the nylon preload spacers today and I now have my shocks ready to go but what quantity of oil should I put into them??? 500cc is a number I have been told. Please dont start talking about air gaps :smt091
yorkie_chris
24-03-10, 05:17 PM
Sorry, you need to set the air gap.
Sorry, you need to set the air gap.
Right so lad,enlighten me :cool:
yorkie_chris
24-03-10, 05:20 PM
Do you just need a recommended setting, or do you need a walk through of how to set it?
Do you just need a recommended setting, or do you need a walk through of how to set it?
Recommended settings and a rough guide. I done it before but it was on an enduro machine
fastdruid
24-03-10, 05:39 PM
Remove springs, take a piece of wire, measure the 'air gap' on this and bend at 90degrees so the 'air gap' is measured from the end to the bend. Place this so it dangles into the fork leg, fully compress the leg and pour in the oil until it just touches the end of the wire. Remove wire and 'pump' the leg about 5 times (being careful that some design of forks will spray oil out of the top!), replace the wire and top up again. Repeat until the oil level does not drop.
Put in springs and for future reference measure the air gap again, then slide the fork leg up and fit caps.
Druid
fastdruid
24-03-10, 05:40 PM
Here are standard heights
http://www.fastdruid.co.uk/albums/tmp/Fork-Conversion-Details.jpg
Druid
yorkie_chris
24-03-10, 05:54 PM
pumping fork leg like that won't work, you need to pump the rebound rod up and down to get the air out of the cartridge.
fastdruid
24-03-10, 05:59 PM
pumping fork leg like that won't work, you need to pump the rebound rod up and down to get the air out of the cartridge.
You are totally right, I'm getting myself confused between RWU and USD. :)
Druid
yorkie_chris
24-03-10, 06:01 PM
No you're not.
You're getting yourself confused between damper rod and cartridge.
Just for everyones info the oil capacity for each fork leg (as I now found outt) is 509ml :)
fastdruid
24-03-10, 07:14 PM
No you're not.
You're getting yourself confused between damper rod and cartridge.
No I'm not, I pump them while holding the damper rod at the top. NC30 and similar type design I loosely screw the cap back on first as it prevents oil squirting in my face.
Just for everyones info the oil capacity for each fork leg (as I now found outt) is 509ml :)
Yes but you cannot rely on that as you may have some oil left in there.
Druid
yorkie_chris
24-03-10, 07:49 PM
No I'm not, I pump them while holding the damper rod at the top. NC30 and similar type design I loosely screw the cap back on first as it prevents oil squirting in my face.
Ahhh, AFAIK the NC30 uses a recirc type adjuster so oil is designed to shoot out the top rather than just bypassing piston
Right Ive added 509ml of 5WT Rock Oil and I have an oil level of 155ml when I put my steel rule into the bottom of the shock. Ive followed the GSXR service manual as best as I could so do I take out some oil to get my 101mm reading???
Yes but you cannot rely on that as you may have some oil left in there.
Druid
Im guessing your right after seeing my current problem :-dd
yorkie_chris
24-03-10, 08:20 PM
You're doing it backwards by the sounds of it, you compress the leg and measure the distance downward from the top to the surface of the oil
You're doing it backwards by the sounds of it, you compress the leg and measure the distance downward from the top to the surface of the oil
Post #23 by fastdruid. Chart says oil height 101mm :confused:
fastdruid
24-03-10, 08:25 PM
No, you measure from top of fork *down* to oil level.
Druid
yorkie_chris
24-03-10, 08:26 PM
I am thinking it means air gap, the top of the cartridge needs to be submerged and I reckon the cartridge body is longer than 100mm.
Also everybody measures fork oil in terms of air gap.
Measure air gap from top down with the leg fully compressed.
No, you measure from top of fork *down* to oil level.
Druid
****in stupid service manuals..........................or maybe its just me :smt091
Measure air gap from top down with the leg fully compressed.
63mm.............ill get my coat :smt091
yorkie_chris
24-03-10, 08:31 PM
That would be rather harsh!
I am at about 130mm on SRAD 600 fork. You probably need smaller gap for USD fork considering tube size difference.
That would be rather harsh!
I am at about 130mm on SRAD 600 fork. You probably need smaller gap for USD fork considering tube size difference.
Went for 106mm,just to give an extra 5mm :cool: Thanks to yourself and fastdruid for yere help and understanding towards a suspension amateur
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