2005 YZ Preload spacer

Suspenders
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57
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5/7/2014
Location
Alpine, CA US
1/24/2015 7:09pm
Cut the proper length of PVC that matches the diameter of spring for your spacer.
0 to 10mm of pre load is ideal.
Frodad78
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TX US
1/27/2015 7:47am
So I match it to the diameter of the spring? Thanks for the info!

I tossed around getting stiffer springs for my weight but i'm only 160 lbs so I stock springs should work?
Suspenders
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Alpine, CA US
1/27/2015 8:27am
Should be fine with what you have.
Once you put in proper preload up front play with your sag and see if you can improve the bike.
Even different tracks may need different sag.
Frodad78
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2154
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TX US
1/27/2015 9:45am
Suspenders wrote:
Should be fine with what you have. Once you put in proper preload up front play with your sag and see if you can improve the...
Should be fine with what you have.
Once you put in proper preload up front play with your sag and see if you can improve the bike.
Even different tracks may need different sag.
Good info, I'll tear into it this week. Thanks again!

The Shop

DaveJ
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114
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10/10/2006
Location
Los Gatos, CA US
1/27/2015 10:03am
Frodad78 wrote:
So I picked up a mint 05 yz125 a few months ago and I'm noticing some headshake. Appears the front is riding low, rear sag is...
So I picked up a mint 05 yz125 a few months ago and I'm noticing some headshake. Appears the front is riding low, rear sag is good but i'm learning the fork springs on the 05 yamahas are a bit short. Everyone is talking about adding spacers because there is a bit of slack. Where can I get a spacer? Can I make one? I'm apprehensive to put homemade parts in my forks! I googled the hell out of it and can't get the info i'm looking for. Thanks
Hey guys,

The 05 uses two spacers on the spring. One up top around the cartridge and one down below inside the lower tube. One is aluminum the other is plastic with a metal ring.

The bottom plastic spacers is 55mm tall. The top spacer is available in 42, 59 and 125mm sizes. George at Suspension 101 can get these for you.

You can also make spacers with PVC pipe. Use schedule 80. You can also make spacers with Delrin, (my fav) a slippery yet hard plastic. If you do make spacers, the most important thing to do is to keep the angles perfect. Use a good miter saw - don't do it by hand.

With that, you need to consider pre-load. Most MX bikes run 5mm and we agree with this for most applications.

To measure pre-load, undo the rod from the rebound adjuster bolt. Mount the fork in the vice with the top facing down and allow the weight of the lower tube to settle on the spring. The rebound adjuster is removed. Then measure from two points, such as the bottom edge of the upper tube to a spot on the lug. Then re-attach the rebound adjuster bolt, screw it into the lug, then take that same measurement. The difference between the two is the pre-load.

There's more than one way to measure pre-load but this is the general premise.


That said, head shake is an oscillation between the hinge point of the steering and the main chassis. It's caused from either more energy coming into the suspension than it can handle (kinetic to heat) or it's from an inability for the fork to recover fast enough after taking a hit. The later of the two is the most common. In other words, it's not re-cycling fast enough.

With that, there are a host of things that you can do to increase stability and plenty of opinions that come with it. The bottom line, if the fork is valved and set-up correctly, it won't matter what you do with the rest of the bike (sag, fork height, links...etc.).

Yoda wisdom - "deep in the fork, stability begins".
Frodad78
Posts
2154
Joined
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Location
TX US
1/27/2015 11:26am
Frodad78 wrote:
So I picked up a mint 05 yz125 a few months ago and I'm noticing some headshake. Appears the front is riding low, rear sag is...
So I picked up a mint 05 yz125 a few months ago and I'm noticing some headshake. Appears the front is riding low, rear sag is good but i'm learning the fork springs on the 05 yamahas are a bit short. Everyone is talking about adding spacers because there is a bit of slack. Where can I get a spacer? Can I make one? I'm apprehensive to put homemade parts in my forks! I googled the hell out of it and can't get the info i'm looking for. Thanks
DaveJ wrote:
Hey guys, The 05 uses two spacers on the spring. One up top around the cartridge and one down below inside the lower tube. One is...
Hey guys,

The 05 uses two spacers on the spring. One up top around the cartridge and one down below inside the lower tube. One is aluminum the other is plastic with a metal ring.

The bottom plastic spacers is 55mm tall. The top spacer is available in 42, 59 and 125mm sizes. George at Suspension 101 can get these for you.

You can also make spacers with PVC pipe. Use schedule 80. You can also make spacers with Delrin, (my fav) a slippery yet hard plastic. If you do make spacers, the most important thing to do is to keep the angles perfect. Use a good miter saw - don't do it by hand.

With that, you need to consider pre-load. Most MX bikes run 5mm and we agree with this for most applications.

To measure pre-load, undo the rod from the rebound adjuster bolt. Mount the fork in the vice with the top facing down and allow the weight of the lower tube to settle on the spring. The rebound adjuster is removed. Then measure from two points, such as the bottom edge of the upper tube to a spot on the lug. Then re-attach the rebound adjuster bolt, screw it into the lug, then take that same measurement. The difference between the two is the pre-load.

There's more than one way to measure pre-load but this is the general premise.


That said, head shake is an oscillation between the hinge point of the steering and the main chassis. It's caused from either more energy coming into the suspension than it can handle (kinetic to heat) or it's from an inability for the fork to recover fast enough after taking a hit. The later of the two is the most common. In other words, it's not re-cycling fast enough.

With that, there are a host of things that you can do to increase stability and plenty of opinions that come with it. The bottom line, if the fork is valved and set-up correctly, it won't matter what you do with the rest of the bike (sag, fork height, links...etc.).

Yoda wisdom - "deep in the fork, stability begins".
Man I was hoping this would be as simple as putting 7mm spacers on top of the springs...How the hell does yamaha sell a bike with negative preload? sheesh...

So when you say the fork can't recover fast enough, how can this be resolved?
Frodad78
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2154
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Location
TX US
1/27/2015 11:55am
I should add that it only happens when i'm accelerating downhill. I'm also 6 clicks from full hard on the compression dampening.
DaveJ
Posts
114
Joined
10/10/2006
Location
Los Gatos, CA US
1/27/2015 12:06pm
Frodad78 wrote:
I should add that it only happens when i'm accelerating downhill. I'm also 6 clicks from full hard on the compression dampening.
Technically, there is no such thing as negative pre-load. The spring just floats when the suspension goes to full extension.

This can for a host of reasons, one being too short of a spring and another being a spring that tends to settle.

And yes, the 05 was a funky fork so they didn't quite hit the mark on a few things.

Additionally, there are cases where you don't want pre-load on a spring...so perhaps that matter was discussed when the 05 was being buttoned up.

As for rebound rates, you can speed things up by adding pre-load, by running a stiffer spring, by running more oil in the lower chamber, by running thinner fluid, and by changing the rebound shim stack.

The logical process is to the get the right spring, set the right pre-load, set an oil height for end-of-stroke performance, then tune the stack accordingly to match all this.

In general, (and this is my opinion) most of the YZs have too much rebound damping in their forks. Best to adjust the stack.
DaveJ
Posts
114
Joined
10/10/2006
Location
Los Gatos, CA US
1/27/2015 12:25pm
Frodad78 wrote:
I should add that it only happens when i'm accelerating downhill. I'm also 6 clicks from full hard on the compression dampening.
Makes sense.

Obviously as you go down a hill you have a weight bias towards the front, which means the fork is working as the primary damper for the mass of the entire bike and you as the rider.

The more load or more energy that goes into a damper assembly to more likely it is to...um... crack under the pressure...so to speak.

Stability is a bubble. Stay within it, you are fine. Go outside of the line and things start to happen. Head shake is one of the things that happen when you cross the line as to how much energy a damper can withstand.
chillrich
Posts
648
Joined
4/1/2008
Location
Kamloops CA
1/27/2015 7:43pm
I added OEM preload spacers to my 2005 YZ250, maybe 3 each side, wasn't expensive.
scooter5002
Posts
4761
Joined
6/6/2010
Location
Nanton Alberta CA
1/27/2015 10:04pm
DaveJ wrote:
Hey guys, The 05 uses two spacers on the spring. One up top around the cartridge and one down below inside the lower tube. One is...
Hey guys,

The 05 uses two spacers on the spring. One up top around the cartridge and one down below inside the lower tube. One is aluminum the other is plastic with a metal ring.

The bottom plastic spacers is 55mm tall. The top spacer is available in 42, 59 and 125mm sizes. George at Suspension 101 can get these for you.

You can also make spacers with PVC pipe. Use schedule 80. You can also make spacers with Delrin, (my fav) a slippery yet hard plastic. If you do make spacers, the most important thing to do is to keep the angles perfect. Use a good miter saw - don't do it by hand.

With that, you need to consider pre-load. Most MX bikes run 5mm and we agree with this for most applications.

To measure pre-load, undo the rod from the rebound adjuster bolt. Mount the fork in the vice with the top facing down and allow the weight of the lower tube to settle on the spring. The rebound adjuster is removed. Then measure from two points, such as the bottom edge of the upper tube to a spot on the lug. Then re-attach the rebound adjuster bolt, screw it into the lug, then take that same measurement. The difference between the two is the pre-load.

There's more than one way to measure pre-load but this is the general premise.


That said, head shake is an oscillation between the hinge point of the steering and the main chassis. It's caused from either more energy coming into the suspension than it can handle (kinetic to heat) or it's from an inability for the fork to recover fast enough after taking a hit. The later of the two is the most common. In other words, it's not re-cycling fast enough.

With that, there are a host of things that you can do to increase stability and plenty of opinions that come with it. The bottom line, if the fork is valved and set-up correctly, it won't matter what you do with the rest of the bike (sag, fork height, links...etc.).

Yoda wisdom - "deep in the fork, stability begins".


Frodad78
Posts
2154
Joined
1/11/2012
Location
TX US
1/28/2015 5:35am
chillrich wrote:
I added OEM preload spacers to my 2005 YZ250, maybe 3 each side, wasn't expensive.
where did you find them? I've been looking
chillrich
Posts
648
Joined
4/1/2008
Location
Kamloops CA
1/28/2015 11:11am
I looked in the parts list but they don't break it out. I found they info initially on Thumpertalk, maybe do a search there.
Frodad78
Posts
2154
Joined
1/11/2012
Location
TX US
1/28/2015 11:30am
chillrich wrote:
I looked in the parts list but they don't break it out. I found they info initially on Thumpertalk, maybe do a search there.
yeah I found that link, company called MX tech I believe. I emailed them today and they definitely have them!
Frodad78
Posts
2154
Joined
1/11/2012
Location
TX US
2/9/2015 10:43am
Hey guys I"ve never worked on forks like these. I need a special tool to take off the caps? Looks like there is an inner hex inside the cap. My service manual is a little fuzzy, any tips on how to handle this?

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