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Discussion Starter · #1 ·
Hey people, does anyone know how much fork oil each leg has in it from the factory? I read online about 16oz left leg and about 15.5oz right leg but I am unsure if those numbers are correct. Also has anyone measured how much extra fork oil they added (volumetric quantity not height measurement) to each leg to raise the level so it would not bottom out as easily? Thank you!
 

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I raise my level from 148mm to 130mm, that was 27cc of oil. That's what I remove from the fork from 130 to 148mm, I then reset the oil level back to 130mm.
 

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Discussion Starter · #3 ·
Thank you Marthy. :) I am going to attempt removing a little fork oil and replacing it (plus .9 oz extra) with heavier oil to raise the avg fork oil wt to between 7.5 and 10. I may change the springs and oil later, but hopefully this will be easy to do without removing the forks from the bike.
 

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Any drawback to raise oil level like fork seal leak?
 

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Discussion Starter · #6 ·
My guess would be it is not a good idea to over fill it. Marthy has tested his bike quite thoroughly so .9 oz extra is probably safe.

I just need to get 2 oz out of each fork, then fill each side with 2.9 oz of 30w fork oil. That should get the fork oil up to about 9.5w. I only have 300 miles on my bike so the fork oil does not need to be changed.
 

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Can you do that without removing the forks from the bike? Is there a write up somewhere?
 

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Discussion Starter · #8 · (Edited)
I am going to try when the fork oil arrives next week. I will update the thread after I give it a go. I don't believe that anyone has tried it yet. Also, even if you don't remove any fork oil the avg wt will go up to about 6.5w just by adding .9 oz of 30 wt oil to each leg.
 

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Okay. If you don't mind take some pictures. I would love to know how to open the forks and I bet you could even suck most of the fluid out with something and replace it that way.
 

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Discussion Starter · #10 · (Edited)
Well the suspension genie paid me a visit today and magically made my fork oil 9w instead of 5w without removing the forks :) I haven't had a chance to try it out yet, I just wish the genie could have provided stiffer springs along with the fork oil!

Just got back, dampening is better on the bumps but the front end dive feels about the same.
 

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Discussion Starter · #11 ·
Here is how to adjust the fork oil weight.

1. Put bike on rear stand (not necessary but recommended) - Right now they are $25 after 20% coupon at Harbor Freight.
2. Move the instrument display out of the way (3 allen screws on back, 2 allen bolts holding the bracket down)
3. Remove the 4 bolts holding the handlebars in place, remove the 2 caps, move the bars onto the tank on a towel and replace the caps and screws so they are just snug.
4. Loosen the 2 bolts at the top of the triple tree next to the top of the forks.
5. Attach a ratchet strap from the ceiling to the handlebar caps and winch the bike up until the forks are up all the way. (Or have someone help hold the bike up for when the fork springs let go!)
6. Loosen the 2 caps at the top of the forks (24mm?) until they are completely unscrewed.
7. Carefully release tension on the ratchet strap while pushing up on the front end to lower the suspension until it bottoms out.
8. You need a small hose, 1/4" od will NOT work. I took an 18" piece of 4 strand telephone wire and pulled the 4 wires out of the main casing and used the casing as a hose. You also need a graduated syringe that will attach to the wire casing hose (I used a 12ml inkjet refill syringe)
9. Stick the hose in the small hole on the side of the cartridge angling it downward and toward the rear of the bike. It will take some turning and prodding but eventually it will go down about a foot or so. Put the syringe on the end of the hose and pull the plunger out to fill it with fork oil. Then remove the hose from the syringe and eject the fork oil in a 1/4 cup baking measuring cup. Repeat until you wither remove an entire 1/4 cup or you can't seem to get any more fork oil out. I was only able to get about 1/4 cup out of each side.
10. Remove the 5w fork oil from the measuring cup and then pour into the cup that same exact amount of 30w fork oil. Use the syringe to transfer the oil from the cup to the inside the fork cartridge. Then add an additional 22ml to raise the fork oil level (Marthy measured this to be 27ml but I reduced that number by ml because we are not measuring the actual height)
11. You need to do this for both forks, however it is best to remove the oil from both forks before adding anything so you know you can get nearly equal amounts out of each leg.
12. Ratchet the front end back up until the caps are pressed against the forks and tighten them up, then bolt everything back together.
13. In case you wish to change the formula the computation for calculating avg oil wt is:

(%wt x wt) + (%wt x wt) = avg wt

example:

16.75 total oil in left fork because it was filled with 16oz stock and we added an extra .75oz. We removed 2oz of the 5 wt and added 2.75 oz of 30 wt.
5w volume amount = 14 / 16.75 = .836
30w volume amount = 2.75 / 16.75 = .164
(.836 x 5w) + (.164 x 30w) = 4.18 + 4.92 = 9.1w avg wt
 

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Here is how to adjust the fork oil weight.

1. Put bike on rear stand (not necessary but recommended) - Right now they are $25 after 20% coupon at Harbor Freight.
2. Move the instrument display out of the way (3 allen screws on back, 2 allen bolts holding the bracket down)
3. Remove the 4 bolts holding the handlebars in place, remove the 2 caps, move the bars onto the tank on a towel and replace the caps and screws so they are just snug.
4. Loosen the 2 bolts at the top of the triple tree next to the top of the forks.
5. Attach a ratchet strap from the ceiling to the handlebar caps and winch the bike up until the forks are up all the way. (Or have someone help hold the bike up for when the fork springs let go!)
6. Loosen the 2 caps at the top of the forks (24mm?) until they are completely unscrewed.
7. Carefully release tension on the ratchet strap while pushing up on the front end to lower the suspension until it bottoms out.
8. You need a small hose, 1/4" od will NOT work. I took an 18" piece of 4 strand telephone wire and pulled the 4 wires out of the main casing and used the casing as a hose. You also need a graduated syringe that will attach to the wire casing hose (I used a 12ml inkjet refill syringe)
9. Stick the hose in the small hole on the side of the cartridge angling it downward and toward the rear of the bike. It will take some turning and prodding but eventually it will go down about a foot or so. Put the syringe on the end of the hose and pull the plunger out to fill it with fork oil. Then remove the hose from the syringe and eject the fork oil in a 1/4 cup baking measuring cup. Repeat until you wither remove an entire 1/4 cup or you can't seem to get any more fork oil out. I was only able to get about 1/4 cup out of each side.
10. Remove the 5w fork oil from the measuring cup and then pour into the cup that same exact amount of 30w fork oil. Use the syringe to transfer the oil from the cup to the inside the fork cartridge. Then add an additional 22ml to raise the fork oil level (Marthy measured this to be 27ml but I reduced that number by ml because we are not measuring the actual height)
11. You need to do this for both forks, however it is best to remove the oil from both forks before adding anything so you know you can get nearly equal amounts out of each leg.
12. Ratchet the front end back up until the caps are pressed against the forks and tighten them up, then bolt everything back together.
13. In case you wish to change the formula the computation for calculating avg oil wt is:

(%wt x wt) + (%wt x wt) = avg wt

example:

16.75 total oil in left fork because it was filled with 16oz stock and we added an extra .75oz. We removed 2oz of the 5 wt and added 2.75 oz of 30 wt.
5w volume amount = 14 / 16.75 = .836
30w volume amount = 2.75 / 16.75 = .164
(.836 x 5w) + (.164 x 30w) = 4.18 + 4.92 = 9.1w avg wt
Use a length of 1/8 copper gas tubing from a plumbing supply or brass tubing from a model shop attached to the syringe with a length of plastic tubing.This is easier to poke into where you want it.
4mm PU or PE tubing is readily available from pneumatics suppliers.
 

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Thank you!!!


Sent from my iPhone using Tapatalk
 

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If my memory of my dirt bike racing days serves me correctly, I think that if you are trying to reduce the amount of dive you need to look at spring rates and or preload adjustment. Adding oil reduces the air space in the fork which will indeed firm things up, but not until the fork is compressed enough to allow the reduced air space to build pressure within the fork. This is more at the end of the travel than at the beginning of the travel as you would experience with brake dive.

Since you already added heavier oil with no effect, you are probably going to go to a heavier spring rate. Before you do, set your rider sag on the forks to 42mm. With the 42mm sag see how much preload you had to add to achieve the proper sag. It should be around 8mm. My guess is it will be allot more than that indicating that your springs are too soft. There are many factors that come into play with suspension setup: Rider sag, oil weight and quanity, shim stacks, piston design etc... But the most important element-the foundation of proper setup- starts with the right springs. Springs make a HUGE difference in how suspension works and FEELS.

I know enough about suspension to make me dangerous. If I were you, I'd check with Nick from Stoltec. I believe he's probably the most qualified to point you in the right direction....
Good Luck!
Trevor
 

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Discussion Starter · #15 ·
Thanks Trevor, I know I need heavier springs. I should be running .85 or .90 springs. I have the preload all the way in, the springs are just too weak for my weight .I just did this somewhat easy mod to increase the dampening until I get around to stiffening the front end. I live in CA so I will likely be dealing with Race Tech since they are local. I am either going to put in heavier springs or buy those Italian cartridges for like $500 with springs. After doing this I'm guessing that the springs can also be replaced with the forks still on the bike.
 

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I'm waiting on a group buy opportunity for Penskes myself. Suspension will be my final piece to the puzzle. I can't wait!
 

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When I pulled my forks off and tipped the oil out there was only 400mil in each leg.
I filled with 10w and increased volume to factory level, it was better but not much better.
I then got some heavier oil, I think 15w from memory and increased levels to 520 / 500 mills, this made it a bit better again and is what I've been riding on for 12 months but this is only a band aids, when I have the money I'll get some cartridges.
 

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Guys,

Increasing fork oil qty (no more than 10%) will only help the fork in bottoming out harshly, It's an old motocross trick. It has zilch to do with stopping fork dive under braking and more to do with damaging expensive fork seals.

Where is your fork preload settings at... 2 lines from 'full in' for a 200 lb rider? if not why not.

Increasing oil weight will slow the compression under braking but it will still compress the same amount. Only heavier springs will reduce fork dive.... then you need to change the shim stacks on the compression and rebound valves to compensate.

If you haven't gotten around to upgrading your suspension with after market items (that's most of us), then follow the Sport Rider recommended settings... They work.

Sorry MXNUT, I missed your post here.... I'm nearly as dangerous but will defer to your post .... :p
 

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Guys,

Increasing fork oil qty (no more than 10%) will only help the fork in bottoming out harshly, It's an old motocross trick. It has zilch to do with stopping fork dive under braking and more to do with damaging expensive fork seals.

Where is your fork preload settings at... 2 lines from 'full in' for a 200 lb rider? if not why not.

Increasing oil weight will slow the compression under braking but it will still compress the same amount. Only heavier springs will reduce fork dive.... then you need to change the shim stacks on the compression and rebound valves to compensate.

If you haven't gotten around to upgrading your suspension with after market items (that's most of us), then follow the Sport Rider recommended settings... They work.

Sorry MXNUT, I missed your post here.... I'm nearly as dangerous but will defer to your post .... :p
Agree with you.

Fork oil level is a good fine tuning tool but should be last thing on the list.
1. Proper spring rate
2. Set rider sags
3. Damping (internal change or oil change)
4. Fine tune oil level if bottoming out or need a little extra support under hard braking.
 

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Discussion Starter · #20 ·
^Actually fork oil level has one more benefit - for some of us. It allows someone to add some extra heavy oil to raise the avg wt more without having to do it twice (only for those of us that are lazy and want to do it with the forks on the bike). I was unable to suck more than 2oz out of each leg. If I filled it to stock level with 30w the avg wt would have been around 8w, but by adding an extra 22ml I was able to raise it to 9.1w.
 
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