03 YZ250 Forks

Big Daddy

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#1
03 YZ250 Forks
I have a 03 YZ250. I think the midstroke of the forks are harsher than my old 98 cr125 with .42K springs. I have read this issue in the mags, but is there a cheap fix for this. I'm not in to revalving or sending my forks away. Lower the oil and install heaver springs or opposite? Any one read a fix for this? I do bleed the forks after every ride. Stock settings.
6' 190lbs.
 

Seth_88

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#3
Originally posted by marcusgunby
bad valving IMO on all modern YZs.
I have an 03 YZ250, and just installed the Race Tech valves in the forks today. I'm not sure if I need to remove the mid valve or not- is it a bad idea? I'm 175lb intermediate and the stock forks seemed to bottom no matter the oil level or clicker settings. I got the Gold Valves to learn how to do it myself, and it was not that difficult. Are the shim recommendations from Race Tech pretty close?
 

marcusgunby

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#4
I prefer to use a midvalve-it can be made ridable with a check plate but you are missing out on the forks potential.The YZ fork isnt the easiest to modify as you have the 2 piece mid valve piston.The mid is where the YZ forks needs most work.Try leaving the mid in place and using RTs settings and see how you get on.
 
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#5
Revalving is probably the only way to truly get rid of it. Somethings can minimize it but not take it away. I am currently awaiting the return of my YZ forks cause I couldn't take it anymore. I have the correct springs but have to ride with the forks only 4 clicks out to keep from bottoming on jumps. Its not so bad on a prepped trak but after I hit a trail the next weekend it was like hitting curbs repeatedly..ouch.

The design is pretty flawed and I'm not sure as to why it is done. My buddy explained it to me but I can't really recall the details enuff to adequately explain it. His 01 YZ had almost the identical valving but had more shims than mine making his stiffer. All Yamaha did was remove the some shims each year until they felt plusher but this just made bottoming even worse.

Hopefully I'll have a report on the revalving soon.
 

Seth_88

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#6
I tried the bike out yesterday with the new Gold Valves, and it did make a difference. The only place it bottoms now is on one jump that has a slap down landing. The forks seem to be a bit more controlled now. I mainly tried the Gold Valves to learn how to do it myself(not interested in spending $5-$700 on suspension) and it's really not that bad. I'm still unsure about the mid valve removal. What difference will its removal make in the action of the forks? I'm not sure if I'm going to revalve the shock, it seems to work pretty well.
 

Big Daddy

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#7
Originally posted by Big Daddy
03 YZ250 Forks
I have a 03 YZ250. I think the midstroke of the forks are harsher than my old 98 cr125 with .42K springs. I have read this issue in the mags, but is there a cheap fix for this. I'm not in to revalving or sending my forks away. Lower the oil and install heaver springs or opposite? Any one read a fix for this? I do bleed the forks after every ride. Stock settings.
6' 190lbs.
I checked the fork sag, and its 70mm(2 3/4"). The stock springs are .43K. Would going to a .44 be enough? Can this be some of the problem?
What can I do with oil level and springs alone without changing the valving?
 
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Seth_88

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#8
The .44 springs would probably be close for your weight, maybe .45. I weigh 175 w/out gear and I'm on the upper end for the stock springs. You might try raising the oil level to 90mm from the top and see if thet helps with the bottoming.
 
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#9
Got my forks back today and the work on the midvalve was awesome. Could not bottom out the forks no matter how hard I tried. I purposely case some jumps and no bottoming. Only thing now is that they are too stiff on low speed compression. Some shims were added to the low speed compression to hold me over until the midvalve shims came in. This made it stiffer through the whole stroke to compensate for the weak midvalve setup. The low speed stack was left as is for the first ride. I will probably have the low speed returned to the stock setup and leave the midvalve.

THe low speed was pretty bad so I backed the clickers all the way out to full soft and no bottoming whatsoever. This is quite a difference from stock as I had to have the comp. only 4 clicks out to prevent bottoming which I could still do on flat landings. So 17 clicks more towards soft is a DRASTIC change over previous setup. I could feel the forks getting stiffer as they went down. Very cool.

I was also able to blitz the whoops and the forks sucked up everything even if I screwed up. Not something I could have done with stock forks.
 

Studboy

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#10
SpectraSVT, Who did you have do your forks?
 
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#11
My buddy works at Fox Racing Shox. Its not really a company you can send it to. Not sure if a place like Pro Circuit, Factory Connection or RG3 will do that same thing as he did. he has connections at Yamaha too. He also knows all the Factory Works specs as well. This won't help us mortals but he is extremely knowledgeable and resourceful.

He may give up the shim specs if you want the same thing. I still need to get the low speed compression worked out before I am totally happy with it which he says is a 10 min job.
 

Studboy

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#12
Ahhh....Fox Racing Shox. I have those on my Snopro (snowmobile.).
I already sent my forks out to MX-Tech, I was just wondering who did yours so I could compare.
 

Big Daddy

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#13
I think I'm going to put two shims under the springs and recheck the sag. Maybe go with 145mm oil height. Do you think it will help? It doesn't bottom out, just has a mid-stroke harshness.
 

Studboy

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#14
That's how my YZ is. The initial plushness is not great, the mid-stroke is extremely harsh. Almost unbearable for me. I haven't had any issues with bottoming, I actually think that the bottoming resistance is great.
 
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#15
I only had midstroke harshness when the bike was set stiff but it would still blow through the stroke on hard landings. So I had to pretty much set it way stiff to avoid it. If I rode trails I wouldn't have to worry about bottoming and I personally thought the forks were way plush. I just couldn't have both. Now that the midstroke spike is gone I can plush it out again.

From what I understand the midvalve was a stack of shims that were stiff and don't give under small loads like chop or braking bumps. These types of things don't apply enuff pressure for the midvalve to open. Because its not opening you feel every little bump. But under extreme pressure the shim would break away suddenly. As you keep riding, these shims get weaker and it gets worse. You end up blowing thru the stroke so fast its as if there was no resistance.

What my buddy did was make it a progressive stack so it has it own support system that allows it to open slightly on chop but still be strong enuff to withstand a heavy blow. With the extra support it won't weaken like the stock setup would. And it allows the mid valve to give a little in the chop.

This is a elementary explanation. He explains things to me but I don't get all of it so not sure how well this comes across.

Adding shims to the bottom (base valve) will only make the forks stiffer thru the whole range. It will resist bottoming better but only make the midvalve harshness standout even more. Thats why I am having the extra shims he put in taken out of the base valve 2morrow.