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Discussion Starter #21
Top row is OEM compression assembly. All are 6mm I.D.
Ill list compressiin as mm 'thickness x OD' From right to left in pic above:

Nut
1.4x10.0 spacer
0.5x9.0
Special shim with main flow holes
Special Main check
PISTON
0.13x17.5 with slits
0.12x17.5
0.12x15.0
0.12x13.0
0.3x9.0
0.3x16.0
0.3x16.0
0.3x16.0
0.3x16.0
0.3x16.0
1.6x16.0 spacer


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Berksglh-

Thanks for the exploded view. Some of those shims are some real funky things, especially the check plate. Seems like that check plate shim would eventually crack and fail. I've never seen anything like this in any dirt bike or snowmobile. The compression face shim especially, but I see/think they are attempting to create several small "reeds" rather than flexing the washer into a potato chip (or are they bleed holes?). Wonder if this unusual arrangement was designed by the boss' summer intern kid with some zany new ideas. Or, maybe these special shims are A-Kit supercross stuff? :)


Thanks!
 

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Discussion Starter #23
Bottom row is rebound. Will list sizes from left to right (I should have laid them both out this way, but oh well...)

1. Threaded shaft is 7.94mm, or 8mm ID shims.

2. Thick flow hole spacer with small step away from piston.
The rest:
0.3x10.5
0.15x22.5 thin flow hole spacer and check
0.12x22.5 slotted check bypass/main flow
PISTON
0.13x18 special shim with outer slits
0.13x18
0.13x16
0.13x14
0.3x10.5
0.3x10.5
Nut


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Discussion Starter #24
Berksglh-

Thanks for the exploded view. Some of those shims are some real funky things, especially the check plate.
I think the odd shims opposite the main stacks just set up a one way check/flow. The shims with slits on the outer diamater seem to set up main stack bypass holes. See picks. In the gold valves, you drill bypass holes in the piston to allow a calibrated flow to bypass. I dont totally understand it, but thats my thoughts. Good luck, and if anyone messes with OEM valving, feel free to post results here.


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Thanks again for the pics and measurements. This is certainly different than a normal MX fork. But,,,, we're working with only 6" of travel and much greater forces, plus likely a tighter budget at the factory.

There are not many changes to be made to the compression stack, but I'm not looking for a major revision either. I just want to lighten up the lower speed sharp bump harshness and get the fork to move a bit more on the street.

I'll be trying some changes within the next month or so, and report back.

Thanks!
 

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I took a first attempt at revalving the compression today. It's definitely an improvement on those expansion seams in the road and/or manhole cover type sharp edge bumps. I left the rebound as stock.

I'll add some ride updates after I get out for some two up rides.

The Vee fork is actually pretty easy to work on, aside from needing a device to compress the main spring and you will need to buy the Race Tech damper rod tool (~$60).

Here's what I have-

185 lb solo rider, 650# Eihbach rear spring on the stock non-modified OEM shock. (shock internal mods coming later)

Springs- Race Tech .95 Kg/mm with standard preload spacer. No additional spring spacers added.

Fork Fluid- Maxima 5wt at 120mm Be sure to push the damper rod all the way down.

(compression stack data)

Nut
1.4x10.0 spacer
0.5x9.0
Special shim with main flow holes
Special Main check
PISTON
0.13x17.5 with slits
0.12x17.5
.10x12 <- new shim
.10x 18 <- new shim
0.12x15.0
0.12x13.0
0.3x9.0
0.3x16.0
0.3x16.0
0.3x16.0
0.3x16.0
0.3x16.0
1.6x16.0 spacer
 

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Suspension tuning update...

Since the last update, I've been riding some solo rides and several two up rides trips with a 160 lb passenger. Most rides have been on paved country roads at 55-70 mph, with a small amount of rough gravel road. With the above calibrations and stock rebound valving, the compression dampening was a little too stiff on some high speed compression hits and the heavier .95 springs overpowered the stock rebound valving. I have needed to make shim changes a couple of times to dial in the compression and rebound dampening.

After all the tuning, I'm pretty happy with the end results. The forks now absorb those low and high speed sharp hits much better that stock, and the stiffer springs hold the front end up much better during hard braking.

I now need to address the dampening control of my rear shock. My stiffer shock spring (650 lb) sometimes overpowers the stock shock's rebound, making the bike wallow a little bit in certain situations, which then can negatively affect the front suspension's action. The shock isn't horrible, but it will need to be done at some time to complete the suspension upgrade.

As a conclusion, I'd recommend this revalve and spring modification to anyone who is a bit dissatisfied with the performance of the stock fork. The improvements are definitely available. The technical challenges of this mod might not be for many folks, and my settings are not likely be correct for people with other requirements, but there are tuners who can perform the work and they can set it up for your specific needs.
 

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Was a week ago while tuning carb on my sherco 300 trials bike. Top end is great, 1/8th throttle is fat and sputtery. Needed a leaner slide or larger strait section on the needle, but was trying different pilot jets.

I tried double blipping over an obstacle and it hesitated then cleared and launched. Dangerous and should have never hit the obstacle like that. Threw my ballance and hit ground leaning left, put leg down and twisted knee.


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Yup, I know exactly what you mean. Before I decided I was too old to continue hitting trees and things and rode single track in the woods a lot I used to know exactly what I'd done wrong almost before the event was concluded. If I didn't I walked back and figured it out. I don't know how that can be, but it's usually almost instantaneous...my mind goes to braking for a tight turn, rear slides out and I was laughing to myself as I slid down the trail.....
 
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