Question for Greyracer...


19 replies to this topic
  • whiskey wheelie

Posted April 15, 2011 - 08:54 PM

#1

Do you know what stock spring rate is on a 2010 yz450? Ive been told differnt things from .47 to .479 and trying to figure out what I need. Right now I'm getting a little midstroke harshness and not using about 3.5-4 inches average of my front forks even at 1 click from softest... of course this is for cross country and not mx. Im about 165 B ridder and am afraid to drop to too low of a spring rate and make it feel like mush... based on whatever the spring rate is im guessing I need to go about .2 less? Any thoughts would be appreciated!:thumbsup:

  • whiskey wheelie

Posted April 15, 2011 - 09:05 PM

#2

oh and one other thing... I do some moto but not much.. I'd like to have more adjustibility say around 12 clicks so i can go either way if ridin enduro or mx. Tracks up here in n. ca dont have any huge jumps.. and are almost more cross country rough beat up tracks.

  • Steel Panther

Posted April 15, 2011 - 09:33 PM

#3

it should be in the manual

  • dgcars

Posted April 16, 2011 - 12:19 AM

#4

I think the std rate is 0.469
Have you tried dropping the oil level? Are you running any pre-load?

  • grayracer513

Posted April 16, 2011 - 09:33 AM

#5

Stock is a .47kg/mm front and 5.7 kg/mm rear. At 165, you should be running .46 fronts (maybe .45's??) and a 5.4 rear.

The harshness can be addressed in a couple of ways short of a revalve, although I do recommend the complete "Dell Taco" treatment from SMART Performance for the bike.

One thing to check is that you don't have the rebound cranked up to high. If the fork recovers too slowly, it will take the next impact too deep in the stroke with too much spring resistance. Also, the same clicker needle that controls the rebound bleed does the mid valve, so adding rebound adds a little compression. Not a big thing, but it's there. Once you get the new springs, try it with the compression clickers opened all the way up and close them down as needed.

Then use a heavier oil (like a 7wt) in the outer chamber and decrease the oil fill to 320cc.

Do this mod, too:

http://www.smartperf.../YZMODASSEM.htm

Here's why:

http://www.thumperta...ad.php?t=650136

  • Steel Panther

Posted April 16, 2011 - 10:00 AM

#6

Will that 2010-11 spring fit a 06-09?

  • dgcars

Posted April 16, 2011 - 12:30 PM

#7

Will that 2010-11 spring fit a 06-09?


Did you ever try to search a Yamaha parts fiche???? Or is it in the manual...

  • dgcars

Posted April 16, 2011 - 12:49 PM

#8

I think the std rate is 0.469...


Stock is a .47kg/mm front.....


Pretty close.....If the guy is doing woods, what about a 0.44 with a Davej DIY kit. That way everyone is a winner & the OP gets educated? :thumbsup:

  • whiskey wheelie

Posted April 16, 2011 - 02:55 PM

#9

Thanks guys.. I had wr1 revalve it and it was valved for a mix of Mx and cross country.. Mx its pretty good allthough im still about 5 clicks from softest... I love it on high speed until I hit a g out or something where I still am not able to use all the travel. The rear actually feels good for me and sag is perfect so not sure on the lighter rear spring. I dropped the oil level from 350 to 325 and figured that I need to change the front springs. Appreciate the input. Ill drop down. 02 and try that.

  • whiskey wheelie

Posted April 16, 2011 - 02:56 PM

#10

Ive also found im getting too old for Mx so figure im just gona set it up for c.c. soley

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  • whiskey wheelie

Posted April 16, 2011 - 03:01 PM

#11

One other question.. if the rear is meeting the free sag guidlines does that mean my scale is wrong or is that just because of all my gear and water pack. I was told for Mx that would be very close to the same spring rate im running. Wouldn't think c.c. would call for extra free sag when running 104 mm?

  • brentn

Posted April 16, 2011 - 03:01 PM

#12

Stock is a .47kg/mm front and 5.7 kg/mm rear. At 165, you should be running .46 fronts (maybe .45's??) and a 5.4 rear.

The harshness can be addressed in a couple of ways short of a revalve, although I do recommend the complete "Dell Taco" treatment from SMART Performance for the bike.

One thing to check is that you don't have the rebound cranked up to high. If the fork recovers too slowly, it will take the next impact too deep in the stroke with too much spring resistance. Also, the same clicker needle that controls the rebound bleed does the mid valve, so adding rebound adds a little compression. Not a big thing, but it's there. Once you get the new springs, try it with the compression clickers opened all the way up and close them down as needed.

Then use a heavier oil (like a 7wt) in the outer chamber and decrease the oil fill to 320cc.

Do this mod, too:

http://www.smartperf.../YZMODASSEM.htm

Here's why:

http://www.thumperta...ad.php?t=650136


what is the purpose of increasing the oil weight in the outer chamber? I understand (or do I?) that the lower capacity allows for more air, making for a more plush feel, but why the heavier oil?

  • grayracer513

Posted April 16, 2011 - 03:43 PM

#13

Did you ever try to search a Yamaha parts fiche???? Or is it in the manual...

That won't tell you if it will fit. The answer, BTW is no, the new springs are too big to fit an '09 or earlier.

  • grayracer513

Posted April 16, 2011 - 03:47 PM

#14

what is the purpose of increasing the oil weight in the outer chamber? I understand (or do I?) that the lower capacity allows for more air, making for a more plush feel, but why the heavier oil?

The heavier oil makes the oil brakes that prevent harsh bottoming more effective. Bottoming resistance is the only thing at all like damping that the outer chamber oil does, so it has no adverse effect on the rest of the fork's behavior.

The main spring has a linear rate, but captive air is a very progressive "spring".

  • grayracer513

Posted April 16, 2011 - 03:51 PM

#15

One other question.. if the rear is meeting the free sag guidlines does that mean my scale is wrong or is that just because of all my gear and water pack. I was told for Mx that would be very close to the same spring rate im running. Wouldn't think c.c. would call for extra free sag when running 104 mm?


Rider sag should be measured with you standing on the pegs, neither leaning on nor pulling back on the bars. Obviously, at least one assistant is required. I would recheck it.

The whole free sag thing varies a little. 25mm isn't always the right number. What is your free sag?

  • whiskey wheelie

Posted April 16, 2011 - 07:18 PM

#16

Im just past 28 but im sitting on the bike in riding position but bike was bring held...

  • dgcars

Posted April 16, 2011 - 10:42 PM

#17

The heavier oil makes the oil brakes that prevent harsh bottoming more effective. Bottoming resistance is the only thing at all like damping that the outer chamber oil does, so it has no adverse effect on the rest of the fork's behavior.

The main spring has a linear rate, but captive air is a very progressive "spring".


I'm hearing you on this, but not fully understanding your reasoning. Will the heavier oil with its slower bleed rate not have an adverse effect on the search for mid-range plushness.

  • grayracer513

Posted April 17, 2011 - 12:11 AM

#18

No. It won't affect any aspect of damping whatever. All the damping is done in the inner chamber. The oil brakes are only effective in the last inch, and all they do is prevent the fork from slamming into itself metal to metal.

  • whiskey wheelie

Posted April 19, 2011 - 02:09 PM

#19

so gray.. do you think i could get away with .44's? Apparently he said garahan is running stock springs with 300 cc level at 180 lbs dry. I'm about 15 lbs lighter and by no means as fast.. wit hthe stock springs im coming short on bottoming 3.5 inches. Hes thinking i would have full range of motion on the clickers and worst case bump up the oil level from 290 in which im currently at 325.. down from 350. thoughts?

  • grayracer513

Posted April 19, 2011 - 02:37 PM

#20

Leave the oil at 315/325 and use a heavier weight (outers only). The recommended .46's seem high, but going to .44's seems low. Maybe .45's; that's what I'd start with. When you get the springs and oil levels fairly sorted out, consider using 215.VM2.K5 oil. #3 in the inners and the shock, and #5 in the outers.





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