09 YZ 450 Suspension oil in rear


6 replies to this topic
  • honda907

Posted November 11, 2009 - 05:32 AM

#1

I have 32 hours on my 09 450 YZ. My question is, does Yamaha have a specific oil for the shock like they have for the front forks? I have the $25 a bottle KYB S1 oil for the forks and was real happy. Worked just like new. What do you use for the rear? I assume pressure is 148 psi like all the other KYB stuff.

While I am on the subject of rear shocks, at 32 hours (never in mud), should I also replace the foam bumper? They bike only seen races on race day. no midweek practice ever.

  • kawamaha

Posted November 11, 2009 - 06:05 AM

#2

it's called KYB K2C

  • grayracer513

Posted November 11, 2009 - 11:20 AM

#3

The Yamaha name for the same product is "Suspension Oil S1".

I use 215.VM2.K5 from SMART Performance. Great stuff, and more durable by far than the KYB fluid. While you're in there, you may want to tighten up the rebound stack by adding base shims. Not sure if the '09 is any better than the previous models, but YZF's notoriously have too little initial rebound response at the rear. Attempting to correct this with clickers doesn't really work because then the higher speed response becomes too great. The result is that the rear wheel stays behind the front much better, and most of the kick goes away.

The bumpers are pretty tough. You be the judge, based on what it looks like, and how hard you ride.

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  • honda907

Posted November 11, 2009 - 11:41 AM

#4

I think the rear works good, and I have won almost all my races this year, so a revalve is not in order. I just want the same performace that I had(or have) and I would be happy. So the stuff from Yamaha that I use in the forks can be used in the shock?

I know what you mean about the springy rear end, but I find when ridden hard, it worked better than FC revalve on my Honda450. Even had a promoter hold my bike once at the gate of the first moto and he thought the rear felt very lively. I said I know. Second moto he said it worked OK for me!

Anyway, I was happy. So happy that I will buy another 09 over a 10 if the bike has a major flaw this year. Only thing I thought the bike needed was a little better steering on flat ground. (maybe it needed a pipe, but I put on a DrD after I broke it in in January. I also changed the pilot, needle and leak jet when I changed the pipe). Maybe it is the Bridgestone tires (403/404 combo I think). I have a set of those Hard track Michelins (HP4) that I never tried, but probably will this winter indoors. They worked good on Hondas. Anyhow thanks for the info.

Edited by honda907, November 11, 2009 - 11:57 AM.


  • mywifefarts

Posted November 11, 2009 - 08:24 PM

#5

The Yamaha name for the same product is "Suspension Oil S1".

I use 215.VM2.K5 from SMART Performance. Great stuff, and more durable by far than the KYB fluid. While you're in there, you may want to tighten up the rebound stack by adding base shims. Not sure if the '09 is any better than the previous models, but YZF's notoriously have too little initial rebound response at the rear. Attempting to correct this with clickers doesn't really work because then the higher speed response becomes too great. The result is that the rear wheel stays behind the front much better, and most of the kick goes away.

The bumpers are pretty tough. You be the judge, based on what it looks like, and how hard you ride.


Grayracer are you saying the shock has to much rebound damping at low speed? Or in other words isn't able to rebound quickly enough without compromising it's action during high speed movements? Not trying to be a smart ass, just trying to hopefully confirm my correct understanding.

I'm sure I read somewhere that another comon mod for the '06-'08 shock was to somehow modify the piston like that of the '08 and later. Are you aware of this at all? If so what exactly is done and what effect does this have?

  • grayracer513

Posted November 12, 2009 - 08:14 AM

#6

Grayracer are you saying the shock has to much rebound damping at low speed? Or in other words isn't able to rebound quickly enough without compromising it's action during high speed movements? Not trying to be a smart ass, just trying to hopefully confirm my correct understanding.

I'm sure I read somewhere that another comon mod for the '06-'08 shock was to somehow modify the piston like that of the '08 and later. Are you aware of this at all? If so what exactly is done and what effect does this have?


Actually, read again. I'm saying exactly the opposite; the shock has too little rebound damping at lower speeds, but has more at high speeds. So, if you trim the clicker way in to correct the low speed, the high speed is off. The response curve of the valve stack is just wrong the way it starts out. Dave Johnson had me restack the rebound valve with an increased number of thicker shims to keep the valve from opening so easily at low speed. It made an enormous improvement in the bike's stability that I simply cannot emphasize enough.

The high speed piston mod requires disassembling the piston from its valve stack and enlarging the holes in it to match those of the '08. Pretty simple.

  • honda907

Posted November 19, 2009 - 05:37 PM

#7

I found the right oil. Enzo racing has it. Just ordered it from them.

K2C rear shock oil. http://www.enzoracing.com/parts.html





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