fork tuning for enduros

Re: fork rebuild

RT = race tech correct.

the 'air bars' mod looks a very cheap mod to try. it's only $30 in the states.

the BV pistons? well i have a pair that are spare so i can do a back-to back test, i feel i have nothing to lose as i have all the equipment.

you may have heard of the modification whereby you drill three 5-6mm holes 20mm up the inner leg from the bottom. seveeral Ktalkers have done it and say it's good. it came from a couple of suspension tuners.

you sound like me viking, you feel that only a "died-in-the-wool" rider should suggest that it works and until then you are cynical! i agree!

as far as the mid valve goes and the rebound i believe that i will try the mid valve stack from the '06. ok, ok a later fork but i feel still worth while! as for the rebound-can you help? i run 4 x (24mm) x .1 shims and i'm told that 3 of is the minimum or they may break up?

can you recommend one please?

BV (was 24 clicks out w/ .46 springs) is: 24, 24, 24, 24, 24, 14, 22, 20, 18, 16, 14, 13, 12, 11, 9 (x .3), 18 (x .2).

will try std '06 525EXC at: 24, 24, 24, 14, 24, 24, 24, 22, 22, 20, 20, 18, 16, 14, 9 (x .3), 18 (x .25)

this has been also modified to remove the two underlined above.

the mid valve and the rebound i'm really strugglling with. the 'chat' on ktalk is all jargon and never written analytically.

i have (rebound is 15 out):
this is the check plate/mid valve = 4 of 24 x .1
then the piston,
then the rebound assembly which is:
4 x delta shims followed by:
15, 20, 18, 16, 14, 10 (.2), 10 (.2), 16 (.25) then the nut.

first of all, am i clear!!!!
secondly, do i have the understanding of it?

what i MAY try (let me know please!) is:
24 x 3 for the check plate/mid valve
then piston and 4 x delta again then

A) 14, 20, 18, 16, 14, (may add 12 & 11 to slow fast rebound) 9.5 (x.3), 9.5(x.3), 16(.25).

B) 21, 20, 18, 16, 14, 9(x.3), 18(x.25)

all with 1.4mm of float. 130-135 air gap.
whilst i have a 'handle' on the BV and i'm ok. i can't fathom the CP/rebound and the mid valve.

regards

Taffy

Re: fork rebuild

Hey Taffy thanks for the Lottery numbers! Next time just PM them to me!

Re: fork rebuild

Taffy this is hard to explain but ill give it go you can put 06 midvalve stack
on your 02 cartridgerod valve but it going to be the same as what you have. Difference between 02 and 04,05,06 what you call check plate it has
ability bend the shims on newer cartridgerod valve where as the 02
can not bend the shims and this is what I would modify (Idid that on my 01)so they can bend,
3 shims on the mid valve is on the marginal side 4 is better, ultemetly
what your are trying acomplice to fill rebound side completely without cavitation ( airbubbles bad for consistency) and control compression in what cartridge rod displaces in volume thru bottom valve how to get there is hard even WP has not figured out completely
midvalve 4, 24x.10 1, 22x.10 1, 20x.10 1, 18x.10
rebound 4, delta 24x.10 1, 16x.10 1, 20x.10 1, 18x.10 1, 16x.10 1,14x.10
2,9.5x.30 1, 16x.25 thats for 04 FE450
I dont understand what benefit hole drilled in location would have,only problems if seal leaks oil would leak out in a hurry
oil height I run 125mm more than that and fork progresses to harshly
for the woods I run one .42 and one .44 spring two .44 was a little harsh
also I run Novation ss bottom valve benefit is that its so flexible moto x
not a problem just dail in next weekend tight long woods ride just dail in
beats take forks off remove bottom valve revalve
hopefully you understand midvalve/rebound otherwise let me know
secret to suspension evaluation just change one thing at the time
hopefully your brain wont catch fire after reading this and thinking about it
:roll:
VIKING

Re: fork rebuild

i understood it all except the expression "any more than (125mm) and fork progresses too harshly". i figure anywhere around 125-140 is what you're saying.

which is the rebound side? the upper spring side i presume!

i have been on ktalk so much lately gobbling up the info. it appears that riders are turning the mid valve into a stack very similar to the BV in some ways.

if you want a really good read over there (and you're registered) put in "8mm" to the search. it's really deep and in the next few weeks as i start to make changes and 'feel' those words i shall know i hope all they do.

Q:as i have only got 4 x 24 on the mid valve which way up should this stack face? i'm guessing from the handlebars down (so to speak!) 18, 20, 22, and then the 4x24.

Q: i look at the rebound stack that i have and i wonder why you need shims? what bit "gives!" the delta shims don't look like they move! and i don't (at present but will with your advice!) have any 9.5 ( by .3) clamping shims. i have 2 of 10mm @ .2 and wonder if my tuner had run out or maybe he knows something?

my rebound was on the middle setting so i'm not too worries about small differences here!

regards

Taffy

Re: fork rebuild

Taffy I expressed my self incorrectly RE oil height what meant was less
air pillar makes fork progress too much so what you are measuring is the
air pillar its like increasing compression on an engine 115mm oil height
would resist bottoming out better than 130 mm oil height
The midvalve would be on top side of piston (rod side) and rebound would
be on bottom side (cartridge side) having a midvalve with same shims as
bottom valve create next to no rebound control cavitaion air in cartridge
think of hydraulic ram if where to compress the ram oil come out + side
and air would sucked into the other - side the cartridge in your fork is just
like a hydraulic ram as you compress cartridge assm. oil would come out of
bottom (+ side) and no oil would be on other side of piston unless you made provision fill up other side of piston (- side) thats what the midvalve
is there to do and the rebound shim stack controls when cartridge assm.
is extended this part of how it works is little hard to comprehend
as oil fills up rebound (- side ) there is going to be difference in volume
between (+ side) compression side and (- side) rebound side the difference is volume that cartridge rod displaces as the cartridge is compressed the cartridge volume is then forced thru bottom valve
where you control compression and there is a replenish check valve
(within bottom valve) to refill (+side) compression side as cartridge is
extended
02 midvalve is a gap control check valve newer midvalve is a gap/flow
control check valve since we are dealing with compression of cartridge
in a wide variety of speed thats why a gap control check is limited in
controlling flow / ability to refill (-side)rebound of cartridge
I am writing this so I am clear how it works I am not trying to cynical or
anything else I am just giving you info I am not trying to better than
whom ever at Ktalk its just my opinion and experiece
You can go about suspension different ways you seems to just try it to
see what happens (maybe I am wrong) Personally I like to be more result
oriented exsample fork bottoms to easy you get my point
just thought of midvalve dont turn wrong side of piston up
from top 4, 24x.10 piston ?, delta 24x.10 rest of rebound stack
yes rebound stack takes bit to move
Merry Xmas
VIKING

Re: fork rebuild

Viking

that was an excellent article. i really enjoyed reading that!

i have again taken the liberty of laying it out as i would speak english and i apologise again if you feel i have been rude in doing this. i don't meant to be. it's a habit i have that i will ignore something until when i go for it i really do GO. FOR. IT. so suspension is in at the moment!

when i roadraced back in the eighties and nineties all i could do was adjust the oil and rebound. didn't learn a thing except the preload etc.
the forks were called 'marzzocchi magnesiums'.

anyway here it is:

Taffy

I expressed my self incorrectly with reference to the oil height. What I meant was that less air pillar makes fork progress too much so what you are measuring is the air pillar. It's like increasing compression on an engine: 115mm oil height
would resist bottoming out better than 130mm oil height will.


The mid valve would be on the topside of the piston (rod side) and rebound would be on bottom side (cartridge side). Having a mid valve with the same shims as the bottom valve creates next to no rebound control because of cavitation air in the cartridge. Think of a hydraulic ram, where it compresses the oil and comes out the other side, air would be sucked into the oil (airation). The cartridge in your fork is just like a hydraulic ram. As you compress the cartridge assembly, oil would come out through the base valve and no oil would be on the rod side of the upper piston unless you made provision to fill up other side of piston (- side).

That's what the mid valve is there to do (let oil through un-airated to the rod side) so that the rebound shim stack controls when the cartridge assembly is extending. This part of how it works is a little hard to comprehend: as oil fills up the rebound (- side ) there is going to be difference in volume between (+ side) compression side and (- side) rebound side. The difference is volume that the cartridge rod piston displaces. As the cartridge is compressed the cartridge oil is then forced through the bottom valve where you control compression and there is a replenish check valve (within the bottom valve) to refill (+side) compression side in the cartridge as the cartridge is extended. The '02 mid valve has a gap control check valve, newer mid valves have a gap/flow control check valve. Since we are dealing with the compression of the cartridge in a wide variety of speeds that's why a gap control check is limited in controlling flow/ability to refill (-side) rebound of cartridge (*1*).

I am writing this so I am clear how it works, I am not trying to be cynical or
anything else I am just giving you info. I am not trying to be better than
whom ever at K-talk, it's just my opinion and experience. You can go about suspension different ways and you have to just try it to see what happens (maybe I'm wrong). Personally I like to be more result oriented. Example: fork bottoms too easily. You get my point.

Just thought of mid valve: don't turn wrong side of piston up from top 4, 24x.10 piston, delta 24x.10 rest of rebound stack. Yes rebound stack takes a bit to move!

Merry Xmas
VIKING

ok, well first of all did i understand you?

secondly the only piece i didn't follow was the piece marked (*1*).

this is my take on things.

the idea of a BV and a MV working on the compression stroke in the cartridge area should be excellent. the idea that rebound is only needed on the upper piston is also fine. what i don't get is why do the two sides of the upper piston (as opposed to the base-valve piston) sit facing the wrong way!

the oil is given a terrible time!

when in compression, the upper piston should have the compression/mid stack facing the oil!!!! it should be the other way round, then when we have oil above the upper piston and go into rebound the oil should face the rebound instead of the mid stack!

they are in fact both facing the wrong way.

the oil should get free passage through the second part of the rod piston but infact what you're saying is that by the time the oil has gone through the rebound then the MV, it has cavitated and airated (milk shake or guinness being served!).

it seems to me that the piston should be turned upside down on the rod and the oil be given free passage on "the far side" in whichever direction it goes. that way: in compression the oil goes through the MV and gets free passage through the rebound. then in rebound the oil goes through the rebound valve and gets free passage through the MV.

but i understand where you're coming from. you're saying that if we stop oil going through the upper piston with lots of tight 'shimming' we have less oil and it's in a poor condition for the task of it's rebound work. i don't know if you have been to ktalk but cavitation/airation isn't even a consideration.

my opinion is that if both valves have shared the work the oil has been sent through two places slower than one place very quickly then like a good pint of beer it will arrive in better condition!

interesting! i shall now dwell on that over the cockrill(sp?) tomorrow!

merry xmas and thanks viking.

Taffy

Re: fork rebuild

Viking i have drilled the holes talked about on ktm site only two holes 5mm dia 175 mm from tube end. I was triying to get rid of air build up and make fork action smoother and it worked no air build up at all now and smoother action i have since drilled several customers forks ktm 400 04/yzf 250 03/klx 300 99 and a few others the customers are all very pleased with the difference it has made with the ktm i also removed the middle bushing to try to get the fork action smother it seams to be better at slower speeds

my bike is a 02 470 fc and i am trail riding foresty and farm land river beds etc i have changed valving a lot but only base valve the fork would deflect when hitting square edges very dangerous in tight forestry you would have no idea where the bike was going to go now its great i have also revalved the rear shock and gone to a straight rate spring i have made a bleeding tool that screws into the compression adjuster and i make and sell nitrogen valves similar to the race tec screw i get 200 made at a time and only works out about $1 each like the race tec item there is a limit to how many times they can be used before they start leaking but at that price who cares the screw i use is a 5mm allen head stainless item looks nice and is small enough to go on a lot of valveless shocks after rebuilds
so far no one has mentioned two stage valveing thats what i ended up with soft for roots and solid enough for big sand woops ANY WAY IT CHRISTMASS DAY HERE and ive got to get organised

Re: fork rebuild

nzberg

i hope you'll give me the address of your shop as i have a mate coming down to NZ in the new year and i'll ask him to pop into the shop and purchase a couple of the valves if i may!

please put info up that you have scoured! it all goes into the pot!

UPDATED FORK INTERNALS

it appears that the fork internals were updated in 2003. new rebound and comp taps as well as new rebound and comp needles. has anyone any info or pictures? anyone updated theirs at the shock gurus?

i have picked up a picture from ktalk of the rebound taps and i'm pretty sure all i need to do is a very simple machining job but could do with it confirming. it looks-in simple terms that the top of the nut can be machined back to create a step from the 10mm shoulder down to the nut instead of it being level.

sorry only geeks will know this one!

regards

Taffy

Re: fork rebuild

Taffy since WP went to a gap/flow control MV rebound control is much better if rebound is packing the sensation would be harch compression
action if rebound is to fast a simiral sensation would be felt so having
rebound adjusted correctly is essential for optimal fork performance
I presume that MV shims is facing up and delta shaped rebound is facing
down thats correct configureration
Happy new year
VIKING

Re: fork rebuild

Hi Viking

am i quoting you correctly here?

Since WP went to a gap/flow control MV, rebound control is much better if rebound is packing the sensation.

It would be a harsh compression action if rebound is too fast. A similar sensation would be felt so having rebound adjusted correctly is essential for optimal fork performance.

I presume that MV shims are facing up and delta shaped rebound is facing down. That's correct configuration.

the above is with reference to my mad idea of the compression (mid) and rebound sides being swopped around yes? sorry but i had a job following.

well anyway, i'm off to get my rear shock today which i've had rebuilt by kevin harris of bury st. edmunds (i bet you yanks lerv a name for a major town like that!). whilst i'm there i'm getting some shims for the front forks so i can attack them next!

regards

Taffy

Re: fork rebuild

No no no no,
it must be:

Taffy, since WP went to a gap/flow control MV rebound control is much better.
If rebound is packing, the sensation would be harch compression
action. If rebound is to fast, a similar sensation would be felt. So having
rebound adjusted correctly is essential for optimal fork performance.
I presume that MV shims is facing up and delta shaped rebound is facing
down thats correct configureration...

Click to expand...

Re: fork rebuild

understood. it's a swedish thing...!

i love the info but following it is another thing.

regards

Taffy

Re: fork rebuild

Taffy said:

UPDATED FORK INTERNALS

it appears that the fork internals were updated in 2003. new rebound and comp taps as well as new rebound and comp needles. has anyone any info or pictures? anyone updated theirs at the shock gurus?

regards

Taffy

Click to expand...

I think of '03 and '04 forks as more of a step backwards, rather than an update. I personally doubt I would copy much of anything out of those. Many people try to change them inorder to become more like your '02 two bushing fork. By "taps" are you referring to valve bodies or shim stacks?

Re: fork rebuild

hello brendan

i'm on about the body for the shims to sit on. apparently the bodies were changed as were the pistins. these can be seen from the side looking through and are adjusted by you as comp and rebound.

i'm hoping 450 is looking for me from ktalk...

the tap of the rebound is considerably improved for sure but as viking has said above (top of second page) they have gone back to two bush.

i hear what you're saying...

regards

Taffy

Re: fork rebuild

Brendan I dont think that 2 bush is any better than a 3 bush fork for us
average rider if you where David Knight maybe I rode a KTM 05 300
3 bush fork back to back with 06 300 I could not feel any difference
besides Kayaba and Showa is using 3 bush design that hasnt been a
problem just my opinion

Taffy now you are seing the difference and you thought I was talking
swedish to you
Happy new year
VIKING

Re: fork rebuild

i'm very pleased with the "handling & suspension" section in the DOC. it is starting to fill out and i'm getting lots of advice from the boys at k-talk on this subject.

see what you think.

like all the docs we start small, fill it out, get too complicated, slim down, cut back and then we're there.

it's not there yet. want to get lots of photos done of all the parts of the bike.

regards

Taffy

Re: fork rebuild

Taffy said:

...
will try std '06 525EXC at: 24, 24, 24, 14, 24, 24, 24, 22, 22, 20, 20, 18, 16, 14, 9 (x .3), 18 (x .25)
...

Click to expand...

Husaberg FE450 -06

Unfortunately, the copy I received was bad so I am not sure about all the figures.

Fork

3x24x.1 14x.1 3x24x.1 2x22x.1 2x20x.1 18x.1 16x.1 14x.1 9x.3 18x.25

4x24.1 16x.1 20x.1 18x.1 16x.1 14x.1 9x.6 (or .8) 16x.28 (or .26)

Shock
Kolben 1

Comp
6x44x.25 2x42x.2 40x.2 38x.2 36x.2 34x.2 32x.2 30x.2 20x.3

Ret
36x.2 36x.25 28x.15 34x.2 30x.2 28x.2 26x.2 20x.3

Kolben 2
Comp
4x40.25 32x.2 20x.3

Ret
36x.2 34x.2 32x.2 30x.2 20x.3


By the figures from Taffy I assume the Husaberg fork is identical with the KTM fork or does anyone know if there are any other internal differences?

Personal I think this is strange since both brands refer to different handling due to different frames. Hence, the question is if this set-up above is the best for the KTM frame, does Husaberg handle better with another set-up?

Re: fork rebuild

mikst

didn't really get that unless you were introducing us to some swedish words!

well i've come to the conclusion - (and let's forget ktm here as they're the same at present) that as long as husey change only one shim per year we will all be dead before we get that nice plush ride we all desire...

forget what's in 'em it's what you do with them when you get them. in the last 6-weeks i've gone from knowing virtually nothing about suspension to knowing EVERYTHING in theory.

i started testing two weeks ago and it's all still on going as i speak.

as this is a fork thread i shall stick to the forks here. i am practicing at swaffham in norfolk every sunday and will keep this up while i have something to test.

the first week i kept the shim stack the same and did four changes that i'd describe as 'free mods'.

1) i did the 17cm oil hole mod
2) i drilled the bottoming cones
3) i polished the cartridge rod
4) i machined the rebound tap to look like ZP3's

i kept everything else the same regardless. the forks were slightly plusher with a lot less spike. the midstroke change felt like it came from the drill mod whilst the spiking will be from the rebound tap.

one thing they don't tell you (although i found it in an old thread only last night) at k-talk is that if you do the drill mod you need an even bigger air gap because oil is filling each side of the chrome tube. the gap may be 125mm like viking says but with this mod it becomes 150mm i suspect. i shall know this sunday!

i agree 99%, before i even start, with vikings views. all i'm not sure about is what part 'aeration' plays when the check plate became a MV in 2004. i think that strong springs should be used to hold a bike 'up' so i'm with 'dangeroo' here. i also believe in my own mind that the valving and shimming should be for 90% of work and then able to "burst open" for those really nasty rocks and sharpe edges.

so the ability for something to 'bend over backwards' both literally and metaphorically to help has to come from somewhere. i like the idea that the MV ('03 onwards) can really arch it's back if needed but otherwise could be a check plate to help reduce aeration. another thing that would reduce this is if both the BV and the MV worked EQUALLY hard and therefore 2 working flowed less and 'aerated' the oil less.

viking, i know you feel it's important that there is plenty of oil on the top side (-) of the mid valve for good rebound work.

at present it's believed that the MV does the work of the BV at a ratio of 3 to 1. i read last night that MXtech and FP who only modify the base valve have got down to 1 (yes sir-1!) 24 shim in the BV. the MV moves all the oil and the 25% the BV gets you control with shims and a screw!

even with a modified and softer MV, the boys are running in most cases no more than 2 x 24s in the bottom. to this end i have softened the LS on my MV and hope to make the bigger changes to the BV at the circuit.

so the testing this week will be with this:
24, 24, 22, 20, 18, 13 and a float value of .048" or 1.2mm.
was 4 x 24 and .056" or 1.4mm float.

if all goes well this is softer in general. i can also remove the 22 as a LS change, the 13 as a HS change or do both and leave a 16 in instead of the 18 for 24, 24, 20, 16, 9 -.3 thick.

as for the BV well i have modified it by pulling out 2 x 24s and a 12 straight away. why? well i want to arrive at the outer edge of softer suspension ready to still only go one way-softer. any more than this and i felt that i would be in the middle of it all. i want to get some practical feel as i get near.

the idea is, i hope, that i'm a few 5-10 changes away from what i want and as i make changes i will feel and understand the differences each change makes. i trust that i'm not too soft already.

regards

Taffy

Re: fork rebuild

Taffy said:

mikst

didn't really get that unless you were introducing us to some swedish words!
...

Click to expand...

It's German. I hoped you could guess if you saw the figures. I will correct it when I got better information than a more or less black fax.

Re: fork rebuild

Taffy said:

mikst

didn't really get that unless you were introducing us to some swedish words!
...

Click to expand...

It's German. I hoped you could guess if you saw the figures. I will correct it when I got better information than a more or less black fax.