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sss fork free piston movement

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Is there supposed to be play in the free piston, and the inner chamber springs (small spring)? Also, I noticed there are a bunch of holes on the plastic.

 

Am I supposed to use the spring spacers with racetech springs? 

 

The bike is an 

'06

 

Thanks

 

<iframe width="560" height="315" src="https://www.youtube.com/embed/_KIcnKBTZnQ"frameborder="0" allowfullscreen></iframe>

 

<iframe width="420" height="315" src="https://www.youtube.com/embed/us0wLY-abcQ"frameborder="0" allowfullscreen></iframe>

 

<iframe width="420" height="315" src="https://www.youtube.com/embed/us0wLY-abcQ"frameborder="0" allowfullscreen></iframe>

Edited by Fasz Kalap

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Some folks drill holes in the stock free piston assembly because sometimes they shatter. Others think drilling affects the feel. Still others replace them with aluminum free pistons with huge chunks machined out of the sides.

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I drilled mine to match what tbt reccomends, and mine had play as well.

 

 

 

 

it came out like this, after a new oring and drilling i put it back together, still works great

110B96CE-FA9C-457B-9C34-B728127344E1_zps

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Is there supposed to be play in the free piston, and the inner chamber springs (small spring)? Also, I noticed there are a bunch of holes on the plastic.

 

Am I supposed to use the spring spacers with racetech springs? 

 

The bike is an 

'06

 

Thanks

 

Cleanly drilled holes indicate the 'free piston mod' was done on those pistons.

Any fractures / cracks in the plastic aren't normal and are signs of damage.

 

Race Tech ICS springs are longer than the stock one, the 15mm or so OEM nylon spring spacers aren't required if you use RT springs.

And yes there is free play in the piston / spring assembly.

Edited by mlatour

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Thanks. I have more than two holes in the plastic piston. I bought the bike used a couple years ago, and it had tbt stickers on it. 

 

Where would the plastic spacer be? Inside the piston? I don't think I noticed any in there

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Thanks. I have more than two holes in the plastic piston. I bought the bike used a couple years ago, and it had tbt stickers on it. 

 

Where would the plastic spacer be? Inside the piston? I don't think I noticed any in there

 

Watch the SSS fork rebuild on YTube. You can see the spacer in the video at 1:10. As the video guy says, you may or may not need the spacer. But maybe your guy left it out?

 

You can also see the spacer at 7:25. This guy shows the drilling process at 7:45. Your owner just added more holes than these guys.

Edited by LSHD

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Just checked, and mine does not have the spacer. The springs I have are longer. Do you have the length of the stock ics spring? 

 

So to confirm, a small amount of play is ok? I have about 1/8" up and down. 

Edited by Fasz Kalap

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Forgot to mention, yes there are some OEM applications where the springs are longer and no spacer is required.

 

Namely YZ (2T) vs YZ-F (4F)

 

In my 2010 YZ125 the springs are short plus a spacer, so longer Race Tech ICS springs are installed without the spacer.

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Thanks, the bike is a '06 yz250. I tried to find out if it needs a spacer or not, but the couple of fiche I have looked at online, do not show the parts for it. The owners manual doenst show what is inside either

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When I look in the KYB parts catalog, these are the applications where the use of a spacer is indicated:

 

2007-2015  YZ125 & YZ250

2007-2011  YZ250F & YZ450F

 

On paper, your 2006 YZ250 should have had a long OEM spring / no spacer

so perhaps at one time yours were replaced with parts from a more recent model.

One thing for sure, you do want to add the spacer to a long spring as it would have too much preload.

 

A few other details I found in the parts catalog : 

 

spacer       :   15mm

short spring : 90mm , rate 20N/mm

long spring :  105-107mm, rate : 20N/mm to 22N/mm (depends on application) 

 

No matter if a short or long spring is used, all the 2006-2015 YZ125 & 250 are OEM specced with a 20N/mm ICS spring rate.

Edited by mlatour

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I have those SDI pistons in my YZ125,

my plastic OEM ones weren't damaged but since I had the forks apart I said 'might as well'...

Edited by mlatour

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It's not a component that you notice a big difference.

 

"In theory"...

Unlike the stock setup, the ICS spring chamber is now vented with the outer tube (thru the tube's bleed holes),

since there is less pressure build-up behind the free piston, that would perhaps make a bit plusher action during initial movement of the fork.

 

Also, since the outer tube's air volume is now increased (the air volume inside the free piston assy now shared with the outer tube),

that would make the fork act like the outer tube's oil height was slightly lower, so less progressive near the end of the stroke.

You can add oil to the outers to compensate for this effect if you feel your forks are too soft near bottoming.

 

When modified, 'free piston mod' plastic pistons will have the exact same effect,

the only advantage to these are that they are made of aluminium and more durable.

 

Are these a necessity...likely not, could be qualified as some 'internal bling' parts,

but also takes a well known part to fail (plastic ones cracking) out of the equasion for some piece of mind.

Edited by mlatour

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Thanks that's good enough for me.

I forgot to mention that one of my stock plastic free piston blew up that's why I need to replace them.

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I wanted to make an update on my free pistons, I ordered an aluminum Set on Cyber Monday from http://mx-tech.com received them that following Friday. I spoke with Matt a number of times and was very pleased with the help I received. Installed with no problems and I'll have to wait until spring to ride but I'm sure it will be great.

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