Advice on front fork springs

[pedro3178]

So after lots of reading it seems this is one of the top things to do to the SV . I wondered if these are any good or simply cheap/nasty and if so what would be recommended please

https://www.ebay.co.uk/itm/Hyperpro-Progressive-Front-Fork-Spring-Kit-Suzuki-SV650-SV650S-99-02/143266005422?hash=item215b51c1ae:g:bdYAAOSw6rRc59Y 3

[Bibio]

dont get progressive springs get linear.


you also need springs for your weight so the preload is correct.

[pedro3178]

dont get progressive springs get linear.


you also need springs for your weight so the preload is correct.

Thanks.

Came across this .... https://www.ebay.co.uk/itm/Suzuki-SV650-1998-2002-K-Tech-Linear-Fork-Springs-35-315/123231769117?epid=626344470&hash=item1cb12f921d:g:IMQAAOSw24RbINP1

It doesn’t state 650S but if I am correct , the 1999-2002 S and non S used the same front springs ?

[Biker Biggles]

Yes, the S and N forks are the same. What you need to work out is the spring rate that you want for your weight and style. I think the standard springs are set up for a ten stone ish rider. Some of us are a bit(lot) heavier than that.

[pedro3178]

Yes, the S and N forks are the same. What you need to work out is the spring rate that you want for your weight and style. I think the standard springs are set up for a ten stone ish rider. Some of us are a bit(lot) heavier than that.

Thanks. I’m a slim guy but would still be 2 stone heavier then if they are set at around 10. It’s the forks pushing into the ground I notice on Hardish breaking. I’ve heard this will solve that but also offer better handling .

[Bibio]

so your 12st?

spring rate depends a bit on your riding style as well as your weight then add a splash of fork oil weight and things can get a bit complicated.

the curvy have a heavy spring rate on the rear shock so you can get away with going a bit heavier on the front. this is the main reason for the pogo effect when riding as the front is constantly nodding.

this all depends on static/rider ride height. best setting that up first.

my advice for what its worth:
take forks apart and weld the rebound holes up on the damper rods and dress the welds.
get yourself some .85 springs. from the link you posted.

get yourself some Silkolene RSF 10w or 7.5w. idealy you need to mix the oil weight to achieve the correct rebound.

set oil height to 100mm.

under no circumstances set your bike up for "race" that most websites advise. your not riding on a race track your riding on a road.. its a completely different ball game when it comes to suspension.

[Dave20046]

As a brand Hyperpro are fine. Or look at racetech. Use the racetech calculator for the spring rate.

https://www.racetech.com/ProductSearch/12/Suzuki/SV650S/1999-2002

(click spring rate calculation).
+1 to what bibio says

Progressive springs are a different product from linear, linear are probably the one you want.

Edit: if you're not big on welding you can get emulator kits (£). Bibio - am I right in saying they're the equivalent to what you're suggesting?

I'd also strongly consider replacing the seals while you're in there.

[pedro3178]

Was enjoying reading until you said weld! :eek: never done any welding unfortunately, is that part a must? Maybe have to find someone if that’s the case

[glang]

I've always wondered if the rebound holes couldn't be tapped so a plug can be screwed in and securely peined in place rather than welding....

[Adam Ef]

Was enjoying reading until you said weld! :eek: never done any welding unfortunately, is that part a must? Maybe have to find someone if that’s the case


There will be someone near you who can do a couple of small spot welds easily and then you can sand them back and clean them up.


Emulators will have no effect if the oil is bypassing them via unwelded holes.


K-tech fork springs are good. Listen to Bibio and search the threads on here for info. I did this a year or so ago and ended up getting my SV very well set up... and then sold it :-(

[Dave20046]

Ah yes.

Different springs (and gen) but this may help you, usefully has torque values

https://www.youtube.com/watch?v=Cj-cb12BCRw

[pedro3178]

Thanks for the advice guys. With regards to parts, is it just the springs, oil and new dust seals to do the job or is anything else required for my gen?

[Bibio]

the SV forks on both gens check valves leak like a bucket with holes in it. this is why you weld the rebound holes, doing this lets you use a lighter weight of fork oil. if you dont weld the rebound holes you have to use too heavy an oil which will slow the reaction time of the stanchion down so you end up with a harsh ride as the rebound/compression cant move quick enough.


springs are to support the weight of the bike and the rider so the suspension is at the correct ride height.
oil is to dampen the movement of the springs.


yes you could drill and tap the rebound holes and put bolts in but they would need to be inserted from the inside of the damper tube with threadlock. the excess bolt coming out of the front would need to be dressed flush to the outside of the tube.


if all the above is done correctly damper rod forks can be about 90% as good as full cartridge and plenty good enough for road use.


emulators mainly control the compression. this is fine if your racing to stop dive during braking but road riding is different with the SV as you should not be relying on your brakes as much but instead using the engine braking and forward planning.


BTW sending the dampers via the post is a way round the lockdown.

[pedro3178]

Thank you very much for the explanation.

Would this be the hole you mean on this diagram that I have marked in red ?

https://i.postimg.cc/B6MwLLT3/IMG-2722.jpg

I will try finding someone to do the weld for me, like you say, I can use the postal service.

[embee]

You'll get a huge improvement simply from the appropriate springs and decent oil, the old 80/20 rule applies (80% of the effect will come from the first 20% of the effort).

In my curvy SVS first I fitted 0.85kg/mm linear K-tech springs and Fuchs/Silkolene Maintain RSF 7.5W oil at about 100mm, didn't close off the rebound holes, and it improved the fork performance dramatically. I'm about 12st.
Sure it doesn't make it perfect, but the improvement is at a level where if it was like that to begin with you probably would be perfectly happy to live with it.

The Silkolene RSF oil has a high "viscosity index" (VI) compared to many other commercial oils, meaning it doesn't change viscosity as much with temperature as oil with a lower VI, the higher the better. I've tried other oils with lower VI and when cold it can feel like the forks are filled with wood. I get RSF from https://www.sportsbikeshop.co.uk/ usually. The RSF 7.5W is about the same viscosity as many other 10W oils. There is a good table on this page showing actual viscosities, http://peterverdone.com/wiki/?title=Suspension_Fluid

As the others say, choose the right springs for your weight and style. I would back the comments about selecting parts for ROAD use, you don't want track values for use on typical roads. Linear springs make life easier to get them right, unless you know what the characteristics of "progressive" springs are then you don't really have a hope of getting it near right, you're just guessing blind.

[Adam Ef]

Agreed. It's quite a process to get emulators set right. If I did it again I'd probably be happy with the right springs and new oil.

[Dave20046]

Agreed. It's quite a process to get emulators set right. If I did it again I'd probably be happy with the right springs and new oil.

To be honest by the time you mess about with emulators I'd be looking at the front end conversion.

On the rebound holes - bit rough, but https://www.amazon.co.uk/JB-WELD-MAC8265-S-TEX-8265-S-Weld/dp/B0006O1ICE/ref=sr_1_3?dchild=1&keywords=jb+weld&qid=1587550530&sr=8-3 ?

[Adam Ef]

To be honest by the time you mess about with emulators I'd be looking at the front end conversion.


I thought about getting another SV and doing the GSXR front end conversion. I ended up just getting a GSXR instead.


If I'd found a naked SV650 with GSXR front end already done though I'd have bought it.

[Dave20046]

I thought about getting another SV and doing the GSXR front end conversion. I ended up just getting a GSXR instead.


If I'd found a naked SV650 with GSXR front end already done though I'd have bought it.
Haha
I found mine remarkably easy. 3 or 4 hour job after sourcing the parts. Was cheaper than emulators too and so easy to adjust.

[pedro3178]

On the rebound holes - bit rough, but https://www.amazon.co.uk/JB-WELD-MAC8265-S-TEX-8265-S-Weld/dp/B0006O1ICE/ref=sr_1_3?dchild=1&keywords=jb+weld&qid=1587550530&sr=8-3 ?


Thanks. I’m going to get a braze torch and some copper rods and give that a go. I’m used to doing solder work so hopefully I won’t F up my forks :rolleyes:

[Bibio]

gsxr front end conversions are easy on a pointy, much less on a curvy as the curvy needs a weird sized top stem bearing.

[Bibio]

Thanks. I’m going to get a braze torch and some copper rods and give that a go. I’m used to doing solder work so hopefully I won’t F up my forks :rolleyes:


get some proper liquid flux.


preparation is everything. clean the damper rods of oil. clean (grind with dremel) inside and out till you take the skin off the metal surface also make sure that the hole walls are clean by taking a drill down it. apply flux to inside and out. heat area to cherry red and start feeding rod into hole. if its done right it should flow like solder. if it wont flow then its not hot enough.


once you have the braze done dress the excess off but dont go mad at the hole point.


as embee has said its not really necessary to do and most folk find it just fine with springs and oil. with springs and oil you dont need to strip the forks right down.

[pedro3178]

get some proper liquid flux.


preparation is everything. clean the damper rods of oil. clean (grind with dremel) inside and out till you take the skin off the metal surface also make sure that the hole walls are clean by taking a drill down it. apply flux to inside and out. heat area to cherry red and start feeding rod into hole. if its done right it should flow like solder. if it wont flow then its not hot enough.


once you have the braze done dress the excess off but dont go mad at the hole point.


as embee has said its not really necessary to do and most folk find it just fine with springs and oil. with springs and oil you dont need to strip the forks right down.


Thanks for the advice, I'll order up some flux

[Grant66]

When fitting the emulators was all the rage, didn't a lot of people just use JB-weld to seal the rebound holes?

https://r.tapatalk.com/shareLink/topic?url=http%3A%2F%2Fforums%2Esv650%2Eorg%2Fshow thread%2Ephp%3Ft%3D177012&share_tid=177012&share_fid=9532&share_type=t&link_source=app

Top post, picture 14.

Sent from an S20 using Tapatalk with that kin cr4p blocked

[pedro3178]

When fitting the emulators was all the rage, didn't a lot of people just use JB-weld to seal the rebound holes?

https://r.tapatalk.com/shareLink/topic?url=http%3A%2F%2Fforums%2Esv650%2Eorg%2Fshow thread%2Ephp%3Ft%3D177012&share_tid=177012&share_fid=9532&share_type=t&link_source=app

Top post, picture 14.

Sent from an S20 using Tapatalk with that kin cr4p blocked


I’ve heard about this but I’m sure it’s not recommended as it can come out

[pedro3178]

get some proper liquid flux.


Having a hard time finding this. Could you point me in the right direction please.

[garynortheast]

I’ve heard about this but I’m sure it’s not recommended as it can come out

I used JB weld on mine when I fitted the Debrix emulators years ago. It’s still in there as firm as it was when I used it to close up the rebound damping holes. Never given me any problems.

[pedro3178]

I used JB weld on mine when I fitted the Debrix emulators years ago. It’s still in there as firm as it was when I used it to close up the rebound damping holes. Never given me any problems.

Good to know. Might be worth a try, would save me buying a torch that I will use once. I tried local businesses but most are closed and one told me they could do it but would take a few months ( no idea on the few months part )

[garynortheast]

Good to know. Might be worth a try, would save me buying a torch that I will use once. I tried local businesses but most are closed and one told me they could do it but would take a few months ( no idea on the few months part )

Again, as Bibio says, preparation is everything. Thorough degreasing and key the surface before applying it. I left mine to go off properly for a good 24 hours before reassembly.

[pedro3178]

Just about to start this. I just wondered, when carrying out the reassembly , is there a special tool required to seat the top bush and oil seal back into place ?

[pedro3178]

It’s fine. I will use masking tape to protect fork. Should have mentioned I want to paint the bottom fork. Got the damper rods out and now soaking in degrease.

[pedro3178]

Happy with how these turned out

https://i.postimg.cc/cCSD2fJn/IMG-2782.jpg


This was the colour of old fork fluid

https://i.postimg.cc/7Z3LykXJ/IMG-2783.jpg

[Adam Ef]

Just about to start this. I just wondered, when carrying out the reassembly , is there a special tool required to seat the top bush and oil seal back into place ?



A seal driver of the correct size (see the smile of the day thread).

Or you can use plastic pipe and u-clamps to make your own.


Whichever you use, drive the top bush using the washer placed on top to get it pushed home without damaging it.

[Dave20046]

Looking good pedro. Safe to say the oil was due

[pedro3178]

Cheers guys.

Managed to get the damper rods welded up

https://i.postimg.cc/3xsTh1Y3/IMG-2786.jpg

[pedro3178]

That's her back together. Obviously I can't road test just now but even the basic push down rebound is night and day to what it was. Can't wait to give her a try.

Big thanks to everyone for their input and help. In the end I went for proper weld on the rebound holes, 8.5 progressive springs and Silkolene RSF 7.5 oil.

https://i.postimg.cc/DwHHxG8c/IMG-2798.jpg

[Biker Biggles]

Proper bike. Not one of those newfangled square things.;)

[pedro3178]

Proper bike. Not one of those newfangled square things.;)

:smt005

[Bibio]

now for some suspension wisdom.


to check that everything has gone well and things are correct.


take the bike off the stands and push down on the front end as hard as you can and let it pop back up. you want the dampening to let the pop come up and stop at rest or just a slight 3-5mm overshoot ten down again. there should be no pogo effect.



weld done :-)

[pedro3178]

now for some suspension wisdom.


to check that everything has gone well and things are correct.


take the bike off the stands and push down on the front end as hard as you can and let it pop back up. you want the dampening to let the pop come up and stop at rest or just a slight 3-5mm overshoot ten down again. there should be no pogo effect.



weld done :-)


Just tried this out. 100% no pogo effect now :cool:

Weld done , I liked that one!

[Bibio]

lol..



you need that little pogo effect of the overshoot but just the up and not down then up again. its very very hard to describe unless you know. the last ting you want is pack down.


if you have used 7.5w silkolene and not 10w and 8.5 linier springs for 11-12st then things should be good.

[pedro3178]

lol..



you need that little pogo effect of the overshoot but just the up and not down then up again. its very very hard to describe unless you know. the last ting you want is pack down.


if you have used 7.5w silkolene and not 10w and 8.5 linier springs for 11-12st then things should be good.


My apologies. It was indeed LINIER springs I used and not progressive!

I filled both forks to 100mm from top of fork ( without springs inside )

What is pack down ?

[Bibio]

packed down is a phononoman that occurres (sp) when you grab the brake and or while hitting bumps in the road. what happens is for each consecutive bump your suspension will move further and further down the stanchion till you have no more travel left. e.g. your rebound cant react fast enough to your compression. to test this you use rumble strips on approaching roundabouts/junctions.


dont worry with 7.5w and .85 linear and 11-12st rider you will be fine as i can guarantee you will have a little overshoot on your rebound.

[pedro3178]

Thanks for all your help.

[WSV650]

Interesting post and Bilbo seems to crop up lot for suspension advice.
Ive a 2005 Gen 2.
90kg fully kitted
15W Oil
K Tech 9.0 springs
pre load on 2nd line from top.

Ive got some modified damper rods to fit along with YSS emulators. Reading this ill start with a 130mm air gap and 2.5 turns on the emulators. I believe this is 2.5 turns from when applying pressure to the spring? I will mainly using this bike for track days with some road riding as well occasionally.

Do you feel this is a good starting point?

[Adam Ef]

Sounds smilart to the setup I had.
Yes, 2.5 turns from where the nut starts to have an effect.
Preload will depend on how you have the back set up and will be amixture of measure the bike sag and then adjiust slightly for feel depending on the riding you're doing.

[gadget]

Well, I've recently done the fork mod on my 99 curvy 'S' and the transformation is like night and day. I'm 12.5 stone and went for k-tech linear 9.0 springs and used silkolene rsf 10w fork oil. This combo suits my weight and riding style perfectly, it's not the very best upgrade available but as a good 'base line' imo it's brilliant.

[WSV650]

Well, I've recently done the fork mod on my 99 curvy 'S' and the transformation is like night and day. I'm 12.5 stone and went for k-tech linear 9.0 springs and used silkolene rsf 10w fork oil. This combo suits my weight and riding style perfectly, it's not the very best upgrade available but as a good 'base line' imo it's brilliant.
Was this with emulators ? If so what did you set the emulators at?

[gadget]

Was this with emulators ? If so what did you set the emulators at?

No emulators, just springs and oil, haven't found the need to delve deeper tbh, It more than suits me and my style of riding.

[Bibio]

Was this with emulators ? If so what did you set the emulators at?

unless your doing track work all the time then emulators are not worth it.

my advice for what its worth is to weld up the rebound holes, fit linear springs for your weight and RSF 7.5 or 10w oil. you must use Silkolene RSF as its known to work.

the SV has not too bad comp as standard but its the rebound thats carp... this is why you weld up the rebound holes on the damper rods.

unless your some god like Rossi then you are never going to use your suspension to full potential. emulators will and do make for a harsh ride on the road unless your willing to take your forks apart for about 10 times. emulators only really work in compression.

if you want to do it right then do as i suggest above but start with 7.5wt oil then use 20w as the 40ml at a time to get it right for rebound. take 40ml out of fork legs then add 20wt and repeat till you get a proper rebound.

[embee]

I'd just add a comment on emulators.
I spent a lot of time playing with the Debrix items and I'm not alone with deciding the holes in the disc need tuning and the valve springs which came fitted were far too stiff. Racetech give info on their recommended (or suggested) valve spring rates.
I ended up adding more holes and opening them out to 3mm, and trying a couple of different spring stiffnesses at different preloads. Eventually I reached a decent functioning emuator. It's quite a lot of faff.
Unless you are prepared to do this sort of tuning I'd suggest a simple spring/oil change as talked about in this thread will give you by far the best bang-for-buck result. It won't be perfect but it'll be plenty good enough for general road riding.

[coldtyres]

unless your doing track work all the time then emulators are not worth it.

my advice for what its worth is to weld up the rebound holes, fit linear springs for your weight and RSF 7.5 or 10w oil. you must use Silkolene RSF as its known to work.

the SV has not too bad comp as standard but its the rebound thats carp... this is why you weld up the rebound holes on the damper rods.

unless your some god like Rossi then you are never going to use your suspension to full potential. emulators will and do make for a harsh ride on the road unless your willing to take your forks apart for about 10 times. emulators only really work in compression.

if you want to do it right then do as i suggest above but start with 7.5wt oil then use 20w as the 40ml at a time to get it right for rebound. take 40ml out of fork legs then add 20wt and repeat till you get a proper rebound.

Hi Bibio.
Can you explain this last paragraph please? I am not sure what you mean.
Cheers Ryan

[Bibio]

Hi Bibio.
Can you explain this last paragraph please? I am not sure what you mean.
Cheers Ryan

rebound and compression in damper rod forks rely on oil viscosity passing through orifices (holes) :smt082. if one welds up the rebound on the damper rods then this helps slow the rebound but keep the compression decent. this is why i always recommend welding up the rebound holes, if you dont then compression can get a too "slow" hard and teeth rattling.

taking into account the above adjusting the rebound (and less so the compression due to the huge oil orifices) is largely via oil viscosity.

now lets fine tune the oil viscosity to get the rebound working properly:
1.you need to be able to do a basic "bounce test".
2.using the bounce test you adjust the oil viscosity in your forks.
3.lets assume that you have put 7.5wt oil on your forks.
4.if the forks over shoot too much when doing the bounce test then take 40ml out of each fork leg and replace with 40ml of 20wt oil.
5. replace fork caps, repeat bounce test. keep repeating the adding of 20wt oil till your rebound has about 3mm of overshoot.

you need to "mix the oil" using a long tube and syringe each time you add to 20wt oil. when you think ist done go ride the bike for a few weeks and then test the "rebound bounce" and adjust if necessary.

the above is a long drawn out process and takes a long time so dont rush things. trust me at the end of it you will be amazed at the difference.

with patience, damper rod forks can be just as good as cartridge.

[coldtyres]

Thanks Bibio!
That all makes perfect sense. I appreciate your effort and patience.
Cheers Ryan

[aesmith]

I blocked mine with epoxy. However when I temporarily used a different set of forks I simply dropped in the emulators with no damper rod mods. I didn't detect a bit difference to be honest. The holes are very small, and some articles refer to them as "bleed" holes rather than rebound.

[Bibio]

aesmith is correct in calling them bleed holes.