2007 YZ250 Weird Fork Issue

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11/18/2020 4:20 AM

So I was riding my freshly rebuilt YZ the other day and my buddy wanted to trade up bikes, so we did. I jumped on his minty, hardly ridden 2007 YZ and ripped on it from the start. Wasn't the best decision I've made..really immature really, I should've ridden it slow just to feel it out. Well, immediately the front end felt a little stiff to me but I figured he just had it set up differently from me. Then...I slammed into a solid face and the front felt like a total brick. After making sure I was good, haha, I inspected..

I stopped, held the front brake, and tried to compress the front end. It would only go down about 2.5" or so. Literally, would not go down any further. Nothing sounds weird, it just won't compress.

What do ya'll suggest for issues? I haven't seen this one before. I'm thinking could be over torqued pinch bolts, an axle that isn't square. All weird issues because he hasn't ridden the bike in a long time and it was fine before. Its a good mystery.

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Motorcycles have been keeping me smiling for 19 years and counting!

The Chap - My YouTube channel. Trying to share the stoke!
https://www.youtube.com/channel/UCqTZ4lNA_xYv6N2DS4L1Now

11/18/2020 4:34 AM

Did you bleed the air out?

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11/18/2020 6:59 AM

Inner damping chambers were likely not bled properly. There is probably excess oil in the upper part of the inner chamber causing hydraulic lock. Either that or something is broken or there is about 3x too much oil in the outer chambers.

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Powerband in every gear !

11/18/2020 7:17 AM

FGR01 wrote:

Inner damping chambers were likely not bled properly. There is probably excess oil in the upper part of the inner chamber ...more

Thanks guys.

My first question was had the forks been bled. He said yes.

To me it seems like oil is bleeding off to somewhere it shouldn't be and continuously doing so because it seemed to get worse (less travel over time).

A disassembly is in order, I'm sure.

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Motorcycles have been keeping me smiling for 19 years and counting!

The Chap - My YouTube channel. Trying to share the stoke!
https://www.youtube.com/channel/UCqTZ4lNA_xYv6N2DS4L1Now

11/18/2020 8:01 AM

Is it plush in the beginning then suddenly stops, or is it more linear? Anyway I would guess the front axle is pinched. Does the thicker part of the axle stick out from the clamp? Bad sign in that case.

One other less plausible root cause that I am ashamed to know is that a 46 mm fork seal is possible to assemble to a 48 mm fork leg. It is however not possible to compress the fork afterwards 😂

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11/18/2020 8:10 AM

It seems totally normal then just hits a stop so I would say not linear. Its fine then brick wall. So freaking weird. The last time he rode it, it was fine. Only thing that's changed is it sat up for awhile.

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Motorcycles have been keeping me smiling for 19 years and counting!

The Chap - My YouTube channel. Trying to share the stoke!
https://www.youtube.com/channel/UCqTZ4lNA_xYv6N2DS4L1Now

11/18/2020 10:07 AM

What FGR01 said and add a bad inner cartridge seal. Oil form the inner cartridge leaks out into the outer chamber and you end up with hydraulic lock of the outer tubes. You won't notice the loss of dampening because the "air spring" effect is so high and then the lock point hits.

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11/18/2020 11:08 AM

This is sounding like a culprit to me! Thank ya'll for the help on this.

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Motorcycles have been keeping me smiling for 19 years and counting!

The Chap - My YouTube channel. Trying to share the stoke!
https://www.youtube.com/channel/UCqTZ4lNA_xYv6N2DS4L1Now

11/20/2020 3:02 PM

Too much oil in the outer chamber. Remove about 35cc of that oil and see how it does.

Paw Paw

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11/21/2020 12:06 PM

You can drain 100% of the inner chamber into the outer and it's not enough to cause hydraulic lock on those forks. Most likely a front axle pinch bolt binding issue, or maybe a bent or dented fork tube.

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