K3 front end

[garynortheast]

I think I'd be trying out the quick and easy option of a lighter fork oil as per Bibio's recommendation first, before any filling/drilling of holes.

[GeorgeRYoung]

See:
https://www.svrider.com/threads/faq-...er-rods.40605/

[Fazer Fail]

well that hurt my head and made me lose the will to live, short on facts and just ranting and raving at each other.

No further forward as some quoted using 20wt and 30 wt oil with emulators I can't get 15 to work let alone 20 or 30!

I have no issue with structural integrity of the damper rods with the additional holes, I may be wrong of course but my engineering knowledge makes me think its not an issue.

I am now at least confident the spring rates are correct and no alignment issues or sticking of the forks.

The emulator is causing the harshness and almost locked feeling, this i presume is down to oil weight, next step is to try lighter oil and go try again.

Now i have modified the damper rods I have no option (other than source replacement damper rods) but to use the emulators and somehow get the low speed compression and rebound correct

[GeorgeRYoung]

There's a one-way valve in the fork which in the SV650 case comes close to the existing holes. Adding new holes above the existing causes the one-way valve to pass over them and compression ceases.

[Fazer Fail]

I am now even more confused so given what you say the forks should now have no compression damping at all and simply be governed by the spring no hydraulic resistance on compression?

So the advice given by Race Tech and YSS is incorrect? I also watched Mad8vcycles on youtube where he shows the dampers rods on his own bike with the extra holes he states more current thinking is 4 larger holes but to my mind the size of the holes would weaken the structural integrity of the damper rod.

You state by adding extra holes causes the one way valve to cross over them and no compression exists? Presume this would only happen at bottom of the stroke then? I notice instructions are that the holes must not be anymore than 10mm apart this would indicate the designers have considered this to avoid what you describe?

I can still feel damping compression, I am considerably heaver than my son so am pretty sure i have pushed the forks as far down as he ever will, I have literally jumped up and down on then and tried to bottom them out the heavier spring is working and the compression damping is still present, I have not experienced the total loss of compression damping that you describe.

If i follow your comments then i must repair or scrap these damper rods as additional holes above the existing will render the forks useless and have no compression damping is that correct?

[Bibio]

You are never going to get perfect dampening with damper rods and emulators. Suspension is always a compromise.

Adding more holes in the damper rod increases compression flow this makes the suspension "softer". A popper valve is just a shim governed by a spring one the popper opens you get more flow. The valve works in tandem with the damper rod holes, so adding more holes allows higher flow so your now going to have too use heavier oil to reduce the flow through the damper rod holes.

The popper shim needs to be set for the bump for hard hits after that the damper rod holes control the flow of the compression with the oil viscosity.

As said there is nothing wrong with the standard compression of the forks on the sv but due to the check valves leaking like a sieve the rebound is too fast which causes overshoot of the rebound causing the pogo stick effect.

Standard dampers with the rebound bleed holes welded and dressed with spring to suit rider weight and 7.5 to 10wt silkoline rsf is known to work.

[GeorgeRYoung]

The pic shows a used damper rod with 4 holes. The scratches indicate how close the one-way valve comes to the existing holes. If additional holes are drilled, the one-way valve crosses them near full travel, and compression damping drops from high to nil.

[Fazer Fail]

So basically the forks are scrap now raging was following YSS and racetech instructions.

Getting to point of giving up so much conflicting opinions should have just left well alone or got another bike for him.

I am now left with forks that are clearly dangerous and can not be used

[Fazer Fail]

Rip it all out start again then I guess

[Bibio]

All may not be lost and maybe just a case of fettling what you have. This will involve adjusting the popper valve and mixing oil viscosity.

Concentrate on rebound by using the bounce test which involves holding the bike by the handlebars applying the front brake then push sharply with all your weight and might then release the front brake at full fork compression or how ever hard you can get them to compress. When the front end stroke returns to the top you are looking for the forks to come up over shoot about 5mm then rest after that. You do not want the forks going up down up. Or going up and stopping. You want a tiny little "bounce". This is after you set the bike sag, dont set rider sag if you have the correct springs like every muppet on you tube tells you, set bike sag only, rider sag is to determine if the bike needs new springs to suit the rider and nothing more.