YZ426 Suspension question


3 replies to this topic
  • spdnjoe

Posted January 07, 2010 - 12:34 PM

#1

Hi guys,
I'm riding a YZ426 and I'm 6'2, 240-250 w/ gear. I went riding after picking up this bike this past weekend and it is totally under sprung. I ride mostly open desert and trails. No MX tracks.

My question is, what springs do I need for my weight. I ride mostly open desert and trails. No MX tracks.

Thank you in advance for your opinions.

Also, I'm in Huntington Beach. Is there anyone local that has done springs and seals before that would help me out. I'm very mechanically inclined in automotive and am a very fast learner. I would love for someone to walk me through it. I will drive to you and bring whatever I need. I learn much better through hands on than reading a book.

thank you

  • grayracer513

Posted January 07, 2010 - 01:25 PM

#2

Race Tech's online calculator calls for .48 kg/mm springs at the front, and 5.6 at the rear. MX-Tech suggests .49 fronts and a 5.9 rear. From that, and from what I've seen, I think I'd probably start with either of the fork springs I could find, and go with a 5.8 at the rear.

Changing the rear spring is a piece of cake, and the only "trick" is that the bumper has to be slid up the shock shaft a ways so the slotted lower keeper can be lifted and removed.

As far as the front, changing the springs is also simple. The manual will walk you through a full disassembly of the fork, which is not at all required just to change the springs. In fact, to do no more than change the springs, you don't even need the forks out of the triple clamps, but you should probably at least change the oil.

Goes like this (if removing the fork):
  • Back the rebound adjuster on the fork cap all the way out until it stops (you may want to note how many clicks it takes to turn it all the way in first, so you know where it was set)
  • Loosen the upper triple clamp pinch bolts and loosen, but do not remove the fork caps
  • Remove the front wheel, loosen the lower triple clamp pinch bolts, and remove the forks
  • Unscrew the fork cap and let the upper tube drop over the lower, exposing the spring, etc.
  • Pull the spring down a little and engage a 17mm open end wrench on the damper rod lock nut. Use this wrench together with a 19mm on the cap to loosen and unscrew the cap from the rod
At this point, the spring is free of the rest of the fork, and can be lifted out of the lower tube. If you want to go into changing seals or bushings, you can continue with that. Note that the damper assembly does not need to be removed from the lower fork tube to accomplish any of this, so unless you have some reason for doing so, it's considerably simpler to leave it in.

Lift out the rebound adjuster push rod from the center of the damper rod and dump the oil out. Pump out the damper assembly. Work some mineral spirits through things, dump that, and after you let that drain/dry a little, chase out the remains of the solvent with a little fresh oil and dump that too.

Refill and bleed the air out per the manual. Oil level is set with the spring removed, the main tubes and damper compressed, measuring the oil level from the top of the outer tube. Go for about 110-115mm.

To install the spring:
  • Pull the damper rod up, and run the nut down the thread to the end.
  • Drop the push rod in and drop the spring over the rod. You will need to capture the damper rod quickly so you can keep it pulled up.
  • Screw the cap on so that it screws all the way down and bottoms on the damper rod. There should be a slight gap between the cap and the lock nut when the cap bottoms
  • Tighten the lock nut and reassemble the fork.

Easier than it sounds. To adjust the rear spring sag:

http://www.tootechra...ension_tips.htm
http://www.tootechra...pension Tip.htm

Tips on setting suspension;
http://motoman393.th...suspension.html

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  • DrThumper

Posted January 07, 2010 - 01:43 PM

#3

I ride a '00 426 with stock springs on mtn trails and open desert. I'm 205 lbs but a few years ago I was pushing 250! At 250 the stock spring set up felt like I was riding a WR, which I feel is just fine for what I use my YZ for.

I had the rear spring pretty much set at it's max compression according to the manual and the front I just keep opening up the dampeners until it extends too fast (clunking) or compresses too slow (accumulated retraction in whoops).

  • Dave102429

Posted January 07, 2010 - 02:37 PM

#4

Hey spdnjoe!

I ride desert too and have the same bike as well. I called Jake from Suspension By Jake. Super cool guy, very easy to work with, and quite experienced. I'd call him up and see what he recommends for springs. I had him revalve/respring my bike. He did an awesome job.

http://www.suspensionbyjake.com/

Suspension By Jake
12210 Michigan St. Unit #26
Grand Terrace, CA .92313
909-680-5564

Suspensionbyjake@yahoo.com





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