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Yz 250 Fork Setup... Shims, Springs, Etc.

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I am new to the forum and have been trying to gather as much info as I can to dial in my 08 yz 250 forks. I have been struggling a lot this race season with fork setup. I wasnt happy last year so i tried some home tuning and made them worse if anything. My shim stacks are very strange compared to anything i have seen on this or any forums. I race hare scrambles in the PA, MD, NJ, and NY. Often the tracks are very brutal and my suspension does nothing but beat me up. Any help on setup would be appreciated... I will include my current shim stacks and spring rates.

 

Rider weight is about 195 with gear

Terrian is mostly PA woods. Rocks, roots, steep uphills and downhills

 

BV

5- 32's

1- 24

2- 32's

1- 30

1- 28

1- 24

1- 20

1- 16

1- 18

1.6mm spacer

Stock bleed stack

 

MV

3- 20's

1- 13

1- 18

1- 16

1- 14

1- 12

1-10

 

Spring rates are stock now but i also have some race tech springs on the shelf.

The main spring is a .50kg and the smaller spring for the inner chamber has a 14 on it.

 

 

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Wow. I race the ECEA series on a 300 Beta, and weigh a few lbs more than you. Your springs are off the grid for your weight! No wonder you get beat up. You want to be on .44s. I'm just starting to get involved with valving the KYBs, but from all accounts your valving looks a bit soft but reasonable. Get a set of springs ASAP.

Edited by GP

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ICS springs are fine for your kind of riding.

 

The main springs are way too stiff and the valving is way too soft (however, float is missing for a final judgement).

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As of now i have the stock springs in... I beleive they are 44's. The 50's came with the bike and i took them out. I just ordered some shims from mx tech last night to help the valving issues but the float is something i dont yet understand. I'm sure there are forums to read but can you explain float Vietze? How is a certian amout of float achieved and what would i want for my riding style/weight? I will probably be opening the forks again tomorrow. Maybe i can make some changes while i have them open.

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44s will be too light.... Around 46s are going to be better to keep the forks up in the stroke...

Curious to what the shock spring is as it plays a huge part too..

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Shock is stock as well, 4.9. I just hit racetech's spring calculator and figured with my rider weight and an oversized gas tank my springs should be .486 in the front and 5.52 in the back. I mentioned before i have the .50's for the front but i only have the stock rear spring. I've been really struggling with the setup this year. In previous years i did really well in harsh conditions. Rocks were my favorite. This year it seems the only time i feel comfortable is in moto style sections, grass tracks, and smooth woods sections. Any kinda of rocks, roots or bumps and my bike throws me. Never felt like that before and i have never had such bad arm pump either... from holding on so tight when i feel like i cant control the bike.

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I think 48s will be on the stiffer side but still better then 50s. The. 4.9 is the way to soft and 5.5 will be a dramatic change...

Do both or don't, the balance of the bike is upset...

Edited by Monk

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My chart says 0.44 and 5.4 , for mx maybe 0.48 but even then I would go 0.46

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Thanks mog... Im working on getting correct springs for front and rear. The other issue is with the valving. I have a good idea where im going with that i just need to get the shims i ordered and try it. Any stack suggestions for a b class woods rider? My plan was to add some shims to the comp base and fill in the missing shims on the tapered portion of that stack. Almost head back closer to stock and go from there.

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I would try what you have first

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Havnt got the springs yet but I did make one adjustment today. After watching a maintenance video I realized I was installing the jam nut and rebound adjustment nut on the bottom of the forks wrong. I wasn't turning the jam nut all the way on the threaded part of the bottom of the damper tube. Which means the rebound adjuster wasn't threading onto the shaft as far as it should either. Could this be too blame for any of the newfound fork issues?

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That would make the rebound possibly inactive and could cause a issue ?

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The number of face shims on that stack is low (soft), but the clamp shim is quite large (16 mm). I'd convert that over to a more common YZ woods setup, with something like 4 more face shims after the crossover and a 14 mm clamp. These two changes might cancel each other out, but at least then you'll be on the map for a more standard setup.

You need to post the float on your mid, that's as important or more important than the stack.

I definitely agree with all of the other comments about spring rates. For your terrain and your weight I would think that around 0.46 would work really well, and 0.44 might be good too. I weigh 175 and run 0.44 in my WR300 2-stroke in the same race series, and they're a tad stiff nut pretty good.

Do you race ECEA? Where in PA are you located? Both GP and I race ECEA scrambles...

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Thanks...my main series is ecea but I usually just hit whatever is close when I have off work. Enduros, d6, neoc, doesn't matter. The weird thing about this year is in past years my best riding was done in the woods and rocks. This year it seems like it's the opposite. I only feel comfortable when I'm riding moto style stuff with ruts to help hold my line. Otherwise the bike just seems to go wherever it wants.

Both front and rear springs are stock right now which is .44 front and 4.9 rear according to racetech.

I won't have the springs for about 2 weeks. I also ordered shims to try and do some testing with a more basic setup on the valving. I will have the float measurement next week.

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Where in PA are you located?

I think there is/was some confusion about the spring rates. In the original post, you said that you've been struggling and the forks beat you up. Was that with the 0.50 springs, or with the 0.44 springs?

Measure the float. That base valve stack is a bit unconventional, but it should work pretty well, quite a bit similar to the "standard" YZ woods stuff. I think that the problem is somewhere besides the base.

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I live in the reading area but i'm originally from north of there...

 

I have the .44 springs in and they have been in for a while. I havnt done much riding at all with the .50's. Took them out not long after i got the bike from the previous owner. I believe the back spring is stock as well. Thats what i was told.

 

I'm going to be riding this sunday so i'll probably have the forks open again early next week. Plan is going to be, check the float and maybe even take it for a test ride with the .50's because i wont have any other springs to try for at least 2 weeks. Just to see how they feel... I can remember liking them when they were in originally but i changed them because i new by the numbers they were too stiff for my weight and i figured at the time i'd rather be under sprung then over. I also got some shims from mxtech in case i need to add or rearrange any of the stack configs.

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I'm actually starting to think the rear might have a lot to do with it as well. Not all the problem but def some... It hasnt been serviced since i got the bike and its beginning to feel softer and softer when i ride.

 

Do you think it would be a good idea to try a yzf250 shock on this bike? I can probably have one to test by early next week with a 5.5 race tech spring. According to racetech that is what i should have for my weight/riding style. I have to study shock differences a little more before i go with it but it seems like it might work. At the very least i can use the spring from the yzf shock on my yz shock. They are the same racetech part numbers according to their tech support.

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0.50 on a 2 stroke is crazy stiff

You only weigh 180 without gear ?

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And you ride woods and rocks , some would even run 0.42 , how much travel do you use with the 0.44 and what oil level ?

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