SK3 fork oil level, weight and general confusion
 

Hi all,
I understand this theme has been discussed ad nausea but there isn't many recommendations for tall and light riders out there for just street riding. I've read all I could and also seen some videos, notably the "what can I do with an SV650S!?" from Dave Moss but the answers seems conflicting with the service manual and Haynes.

My specs:
140 lbs, 5' 10", SV650S K3 (so with adjustable preload)

1) I'd guess my stock springs are fine.
2) I have my preload set to factory (2 lines visible), rear shock on factory (pos 4).
3) I have replaced the old (probably stock) oil for a fresh RockOil SVI 10 (cSt@40C 33.2, VI 170) with oil level 94 mm exactly as recommended by Service Manual and Haynes
4) After the oil change the front end feels more "bouncy", responses faster to road but it was a bit tiring in the first moment. It almost feels like the system was under-dampened.
5) I removed about 20 mm of oil from both forks which improved everything significantly, the ride is smoother/softer but now the front end dives in a bit more.

Am I correct in change for a bit thicker oil (Silkolene RSF 10 with cSt@40C 47, VI 303) to dampen the movement a bit as a good step?
I'm going to check my sag tomorrow - that is actually very important, right? Should I set it to 25-33% of total fork travel (130 mm) with my weight on just by adjusting the preload? And then try to match the rear to the +/- same?

Regarding oil level - some recommend around 110-120 mm gap, I've read that it should be same as fork travel, Dave Moss says 130 mm, manual says 94 mm... What the heck? I plan to do 130 mm gap initially and then I can easily top up if it feels too soft, or is that idea flawed?

Sorry for lengthy post, my head is spinning... Thanks for all advice!

Re: SK3 fork oil level, weight and general confusion
 

it was racetech that started this 130mm gap, they done so for people fitting their emulators. due to measuring the air gap when springs and such are out when you add the emulator it raises the oil level hence the 130mm that racetech recommend. so 95mm-100mm is fine, the less oil the bigger the air spring the plusher the ride.


if you really want to upgrade the front end then you must weld up the rebound holes in the damper rods. doing this will reduce the 'nodding' of the front end as it helps reduce the rebound slop. there is by and large nothing wrong with the SV compression, its the rebound thats proper carp. its all a balancing game, the heavier the oil the harder the suspension will feel.


you only need to set bike sag then check rider sag sizes. this will tell you if you need to change spring rates. why dont you adjust rider sag i hear you say?.. well with the correct spring rates the rider sag will fall within the correct sag setting so no need (this is why we change the spring rates out). its when people are too tight to change out the springs is when people start messing with the rider sag which causes all sorts of problems. remember if you change the rider sag you are also changing the bike sag, you cant change one without the other.


always go 5mm more on sag settings for road use. unlike a race track roads are full of humps, bumps, pot holes and other nasty stuff so you set the suspension up to use pretty much the full range of movement.


public roads are not race tracks so bike suspension needs set up different.

Re: SK3 fork oil level, weight and general confusion
 

I recently put 10 weight Silkolene RSF in my AL7 and it felt better ( or maybe it was the Avon Storm 3D tyres fitted at same time - which are great ) , think is was a bit lower viscosity than the OEM Suzuki stuff, front end does not seem bouncier, just a bit softer ride on the assault courses that are described as roads round our way. Nip across the border into Wales or up to Scotland and the roads are 10x better....

Re: SK3 fork oil level, weight and general confusion
 

I'm not sure exactly what springs the K3 had, but my K1 springs were definitely too soft. I suspect the K3 were the same spec ? (just added a preload adjuster).
At 140lbs plus gear I'd suggest you might consider going to a stiffer linear spring, I have had a couple of sets from https://www.ktechsuspension.com/

I'm about 160lbs (plus gear) and have 0.85 kg/mm (8.5N/mm) linear springs in it which made a huge improvement to the pogo stick original spec. I use Silkolene/Fuchs RSF Maintain oil at 7.5W, which admittedly is on the comfy side rather than firm (suits my riding). I would suggest this rate would be OK for your weight, it's still very compliant.
FWIW, one of the "pleasant" aspects of the Michelin Road5 tyres is that they are very supple at absorbing coarse road surfaces. If you like a plush ride they are just the ticket.
Just my 2p.

Re: SK3 fork oil level, weight and general confusion
 

Thanks for all the input from you, especially Bibio (I checked my sag and adjusted front preload - it feels already better)!




What is you oil level with RSF 7.5W? Its viscosity is very close to the stock Showa SS-08.


I'm thinking about getting 8.0 N/mm Oehling springs after all the reading.

Re: SK3 fork oil level, weight and general confusion
 

Spookily enough, I went for the Ohlins 8.5N/mm and 10W oil with a set of PR5 tyres and the front end is much improved (I'm 12st plus gear) this coupled with a Nitron rear shock and my old K5 is like a different bike and much less knock from the front suspension when hitting bumps at low speed.


Agree that PR5 prone wierdly to punctures (or I am one unlucky sod), but the front has gone 12K and I'm yet to wear out a rear before I run over something disastrous (disposable vape pen and a car key!!??).

Re: SK3 fork oil level, weight and general confusion
 

Indeed, the RSF 7.5W is pretty close to many other 10W oils, so a reasonable starting point.
I think I set the oil level to the recommended book value with the std damper rods, from memory 103mm but that may be wrong. You can always play with levels.

Re: SK3 fork oil level, weight and general confusion
 

Hmm, so my right fork oil seal began weeping today, what a lovely coincidence!
OEM seals ordered...


Can it kill me by riding it or just get oil on my brake pads in the worst case scenario?




Interesting though that measuring my static sag and rider sag (yesterday) I have 20 mm static and 32 mm rider sag. Would that indicate my springs are correct (or even too stiff), aren't they? Maybe they aren't OEM though (bike is 2nd hand with unknown history)...

Re: SK3 fork oil level, weight and general confusion
 

getting oil on your brake pads can! Got a British bike that leaked for years - only managed to stop it when I got hold of a pair of moded oil seal holders that take two seals instead of one. MOT time was not a problem, it was just accepted, but times are different now. I would change them pretty soon before a complete failure. Loads of info on here and Y tube vids explaining how. Not really difficult with care and patience.

You can try and remove any crap with a thin piece of shaped plastic. - I tried it on the SV, never worked, the seals had just gone hard with age I guess

Re: SK3 fork oil level, weight and general confusion
 

TBH front preload is a bit more difficult to set up than people think. it fully depends on the riders riding style. most online vids and tutorials only cover racing setup which is no good for road use.


my advise for this is to set up bike sag for race then add 5mm e.g. if its 30mm then add 5mm so its 35mm then put an indicator like say a cable tie on the stanchion and then check how much movement your using after say 200 miles. i cant remember how much gap there is from the bottom of the yoke to the full fork travel but lets say 15mm you then add 10-20mm for emergency situations so you want your cable tie to be lets say 30mm from the bottom of the bottom yoke. if your getting nowhere near that then your riding style is very smooth with very little heavy braking or the spring rate is not suitable.