This is the original CV spring on a modified piston tap. Well, a part of it is visible anyway, between the hexagonal part of the tap and the MV shim stack. Works fine.
Here are my taps, after and before modification. The mod is not fully ZP3, he made the shoulder, which the MV stack hits before it starts to flex, chamfered with a 30 deg angle that makes the shim stack bear at the edge of the 8 mm hole. Thus flexing more easily.
Picture from Taffys "the doc" for comparison. zp3 on the left. Later model tap on the right hand side.
Regards
Edit:
On shallow washboard bumps and acceleration when the fork was working quite extended it started to top out harshly after a number of these bumps. As if there was not pressure enough in the fork to refill the rebound damping volume at each bump. On large bumps it worked better and deeper in stroke it did. I decided that some of the damping had to move from the mid valve to the base valve in order to prevent the oil from escaping rebound volume.
MV is now at .7mm float and the following stack.
24 0.11 (KYB shim)
22 0.1
20 0.1
18 0.1
Still not a turned 8mm zp3 pivot, instead pivoting on a .60 mm wire ring cut out of an extension spring. Very simple. The MV stack is very soft. It can now flex 2.5 mm before it hits the stop. That could be shim brutality.
Rebound, most of the time, is very near what I want and don't know what else to do now, thus unaltered.
The piston is now removed for modification from the fork without removing the forks or wheel from the bike and wont even have to drop the oil. A 35mm circlip
http://www.seeger-orbis.de/en/index.php?article_id=335&FORM[target_id]=28 under each BV prevent them from falling out, they grip by friction only. The cartridge tube, piston and piston rod, hydraulic bottoming cone, spring guide, spring and lid comes out as a unit. If necessary, a U shaped piece of sheet metal is installed as a temporary preload spacer so that the spring tension is rised to increase the friction in the assembly, it can then simply be unscrewed from the BV and lifted out of the fork. Or just put the spanner on the spring guide as you would anyway later. The BVs will remain in the forks, held by the 35 mm circlips, and their o-rings will prevent the oil from running out on the floor.
BV is almost the same as before but with three 24mm shims added. Nearly all shims .1 mm thick.
valve face
24
24
24
12
24
24
22
20
18
16
14
12
10 .3
18 .2
BV post
Perhaps this BV stack went a little overboard, not too bad really, but might pull one or both of the 24s between the splitter and the 22. Not sure yet if the .7 mm play MV was an improvement over the 1mm one. Might even go back to previous stacks and grind the BV shim faces concave too. like .1mm deep or so.
Edit again:
Went back to the Stock OEM BV just to see what it was like but as expected it was not too good. But it helped me understand what was needed. Far too soft the feeble BV made the fork compress too far and caused too much launching in some cases, given more rebound damping on the clickers to cure it made the fork too taut and irresponsive to rider input. Took a while to realize it. Then tried the stack above altered to plan, that is:
valve face
24
24
24
12
24
22
20
18
16
14
12
10 .3
18 .2
BV post
And it was a lot better than the oem stack.
Best combination with this weak MV at 0.7 mm float so far though was with the first used with it. I thought it was too stiff but it was the other way around. Should not have removed any shims at all but instead added.
Alternatively beef up the MV again, which generally felt good, but I'm afraid that the harsh topping out would return on mild washboard bumps. There is only so much pressure in the fork.
But one thing at a time. My plan is to not stick to any fixed plan but to constantly reassess and react accordingly.
The MV is like an extremely small but very aggressive dog. It is attacking anything that moves but it can do very little harm, if any, or even annoy. A big dog would do the job better but it would need to be more tolerant. In other words; back to a thicker MV to make it more effective and give it more float to make it engage more gently.
And yet another edit;
As you now know I tried a weaker stack for the MV and a smaller diameter pivot using a wire ring on the tap. It really rewarded slowness.
It can now flex 2.5 mm before it hits the stop. That could be shim brutality.
It was, some shims had to be replaced since they deformed (pringle crisp) in very little time. The edge of the 18 mm shim in the MV frequently engaged the 2 mm cut down in both cases, I know because the blueing put on the shim surface wore off where it engaged. It must have saved them and with the wire ring on the tap this 2 mm flex gap increased to 2.5 mm, or even 2.6, which, as it appears, was too much flexing for them to take.
The conclusion is that the 2mm flex gap should be maintained at 2mm to limit the stack flex at full storm or the shims are going to get damaged.
The idea of using 24's only backed with a curved washer in the MV seems even sweeter now. If only I could find any suitable material to make the curved washer...
MV is now at 1.1mm float, back to 2 mm flex limit @ dia 16 mm (by removing the wire ring) and the following stack.
24 0.11 (KYB shim)
2x24 0.1
22 0.1
20 0.1
18 0.1
And I could not feel any difference between 0 to 4 mm of spring preload so now I left it at 3 mm. I fear that the fork will get bouncy riding very steep uphill if there is too much preload but I dont know really.
BV is still
24
24
24
12
24
22
20
18
16
14
12
10 .3
18 .2
Compression adjuster opened 12 clicks. 13 clicks made it harsh and threw you in rocky stuff. What a difference a click makes...
Rebound adjusters opened 14 clicks.
Funny that making compression damping too soft made riding rocks and roots harsher. Now with
more compression shims the fork is soo smooth.
And yet another edit;
MV is now at 1 mm float, 2 mm flex limit @ dia 16 mm. Replaced the 0.11 face shim with a 0.1 shim and added another 0.1 mm 24 dia shim. This is actually almost the MV I started with!
The Kayaba 0.11 shim used as a face shim in the MV doughnutted almost as easily as the original 0.1 shim. Not that it had gone very far.
4x24 0.1
22 0.1
20 0.1
18 0.1
(Next time maybe a 0.15 as the face shim in the MV will cure the doughnutting. Then with some more backing shims to support the 0.15 better. Or the curved washer.)
BV is slightly softened since the MV is slightly streghtened:
24
24
24
12
(This is where a 24 used to be, I pulled it)
22
20
18
16
14
12
10 .3
18 .2
It's actually like the oem BV stack with a 24 face shim added.
Compression adjuster opened 12 clicks.
Rebound adjusters opened 13/14 clicks.
And this time new oil! Level = 130 mm. No, I did not experiment with the oil level at all.
Q8 Fork Oil Light 5, 21cSt @ 40degC, V.I.=219, , same as before.
It works quite well now so I see no reason to open the fork legs again for a while.
I start to think that there are two separate reasons the MV shims are getting damaged:
The dughnut damage is from the port edges on rebound. This damage is limited to the MV face shim only. This takes a long time to develop. Should be possible to suppress by using a heavier face shim.
The pringle crisp damage from being allowed to flex too far on compression. This can happen to any shim in the MV stack, it did, even to one in between two undamaged. It happened within a just a few hours of riding. Seems like the backing, shims and flex limit, is important to stop this from happening.
regards
What do you think?
