Fork Internals Smashed

[cyprice]

I bought my 02 YZ250 in May of this year. Forks have felt a little stiff on the initial stroke so I thought I would take a few minutes today and put in some quality 5w. I got them apart and was greeted with this unhealthy sight.

The preload washers are mangled beyond belief, the top 2in of the white plastic is smashed and the steel bottoming cones are dented.

I got several nickel sized peices of plastic to pour out with the oil which was filthy black and the level seemed quite low. What would cause this? I have bottomed a few times but nothing that felt violent, could have been the previous owner, he was hefty. How should I check the internals for damage? What should I look for beside the obvious bent and broken items?
Thanks,
Cy

 

[cyprice]

Here is a pic of the oil. It barely filled the bottom of this pan. Two legs worth.

Help me get back on the dirt again. I have taken forks most the way apart but understand little of the inner workings.
Cy

 

[dbrace]

That's what happens when you put preload spacers on the top of the fork springs on bumper forks.They must go under the fork spring. They will need a complete tear down and inspection for damage,and no that isn't even close to being enough oil. This repair job will be best left to an expert.

 

[Calcaneus]

I have torn down a grand total of 2 sets of forks in my life, if that tells you anything about my exprtise. I just finished assembling the forks on my 99 WR 400. I believe they are the same forks as yours. The only plastic inside my forks was the washer between the cushion rubber and the metal spacer. My forks had no plastic in the location indicated by your picture. I suspect this was added to increase preload. I would suggest you get a manual with an exploded view of the forks. If I had a scanner I would email it to you. Take a look at motoman393.com for some cheap tools for working on these forks.

 

[marcusgunby]

You really need to strip them down to shim level-that isnt easy for a newbie-i would look at taking them in to a professional-it will cost more but it honestly is a fair job you have on your hands.

 

[cyprice]

Well, I dont know if I would classify myself as a newbie, I did install the Race Tech gold valve and shims in my DRZ a year ago. Those were conventional forks but I assume the difference isnt that great for disasembly and reassembly. I also have the service manual.
Next item, the manual does not show any preload washers in the parts diagram, above the spring or under. If I remember correctly my 426 only had one. What is stock, one, two or none?
I am mostly concerned about internal damage. I can recognize bend shims and tweeked parts but is there something that may not be obviously broken that I need to check while I am in there?
Cy

 

[marcusgunby]

The hard part is getting to the midvalve as you have to unscrew the cartridge.It takes alot of heat and sometimes a few good whacks with a hammer to get it to loosen-a search on midvalve should throw up a few threads on that topic.Im not sure on the preload washers-dbrace will be able to help more on that.The only other things to check is the condition of the damper rod bushes-you shouldnt have any real side to side play.A good clean and feel for if they are damping on compression and rebound should show up any problems.

 

[dbrace]

Stock yamahas have no preload spacers.

 

[cyprice]

Thanks, marcus. I'll check those things. I tore into the forks because the initial feel was stiff, I'll neglect to install the preload washers and see if it softens up any.
Where in the UK are you? I lived in the area around Blackburn for a few years back in the mid 90s durring the madcow scare. You anywhere near there? I miss the english chocolate and bread. Why does every country in the world have better bread and chocolate than the US? Even Mexico kicks our butt in those areas.

 

[bclapham]

i run the preload spacer in the bottom of those forks under the spring as per the manual. the reason they are stiff is the valving- also, if you need to take the cartridge apart you will need to drill the peens a bit using a drill press. mx-tech also has a good download for them forks

 

[Studboy]

cyprice, the 02 YZ250's fork is not my all-time favorite to say the least. (Look at my signature.) I would get them revalved at the same time that I was getting the problem fixed. Mine are going to MX-Tech next month I think for a little treatment.

 

[DEANSFASTWAY]

Terrorism

 

[bclapham]

LOL dean, its a shame you didnt see the spare cylinder head i got of ebay- it looked like a top end bearing failure, but they took the wizzy wheel to it and grinded all of the deep indentations out!:eek: luckily, the head was for a 58mm piston and eric managed to rescue it for me and i have a nice spare now.