2005 YZ450F fork springs and bushings...?

3 replies to this topic
  • ace402

Posted August 26, 2008 - 09:25 AM


So I recently bought a 2005 YZ450F from a former pro privateer. He had Pro-Action revalve and respring his suspension. He said that they went up one spring rate from stock but gave me the un-used stock springs with the bike.

Stock Fork: .46 Shock: 5.3

Currently Fork: .47 Shock: 5.4 or 5.5

Race Tech Recommended Fork: .437 or.44 Shock: 5.2 or 5.22

I'm a 145-150 lb (without gear) novice MX rider with two big races coming up at Millville. TT OEM can get me .438 OEM springs PN# 1C3-23141-40-00 for dirt cheap.

I think I'll keep the 5.3 shock spring but I'm considering getting new fork springs. What do you guys think? Would the bike be out of balance if the forks were slightly softer? Also if I kept the stock fork springs would it give me room to "grow" and become a faster rider without having to do more suspension changes in the future?

The forks are currently leaking, that's what prompted my thinking. "If I'm in there anyway I may as well at least put the stock springs back in."

Also, How probable is it that i'll ruin my fork bushings when I separate the fork tubes? I only orderd seals with out bushings. If I end up damaging the bushings how bad is it to ride on it for a weekend while I get new bushings?

Also, from what I've read in the manual it doesn't look like I'll have to set an oil level, just fill the inner and outer chambers with a set amount of oil? Is that right? I would find it hard to get each fork the same because there will most always be residual fluid in the forks.

Thanks a lot in advance!!

Sorry for all the noobie questions, I just want to do it right the first time.



  • grayracer513

Posted August 26, 2008 - 11:03 AM


No damage will be done to the bushings on separation of the tubes. You can hurt them (bend or scratch) by mishandling during their removal/reinstallation, but if you're reasonably careful, you won't.

The outer tubes are filled with a specific amount of oil. The inner dampers are filled to the point that excess fluid is ejected while making the assembly of the compression valve assembly. ALL air must be excluded from the inner chamber, and the design of the '05 inner chamber free piston makes this difficult, to be polite.

Read the manual carefully. You will be told to fill the dampers with a certain volume of fluid and then stroke the damper slowly several times to work the air out of its internals. Do this slowly, and wait for the bubbles to go away.

Then, you will be told to fill the damper to a level, compress the rod, and insert the valve while allowing the rod to extend. While doing this, hold the cartridge at an angle, and rotate the valve a bit to get air out from under the piston. Once the valve is screwed in, wrap a rag around the top where the two small holes are and, holding the damper at about an 80 degree angle to vertical (top higher than the bottom) compress the rod slowly and completely three to five times. Excess oil, and hopefully any remaining air will be exhausted and can be drained fron the two small holes near the top of the damper.

The '05 is so much more difficult to properly bleed that I wouldn't even open the cartridges unless it was strictly necessary, and it's not, just to change springs. You may want or need to for other reasons, of course.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Ga450owner

Posted August 26, 2008 - 01:39 PM


So figure 160lbs with gear - If time is a issue put it back to 100% stock springs and if you are a fast B to B+ rider you will be happy. I would clean and refill oil in both forks and shock(and Ni), replace seals (always if they leak) and leave 10 -15cc out of the forks, ea side so you can add more if you need at Millville (this will be probably about right for you). Hope you have a scringe - to add oil.

If it is too stiff, even with less oil, or you are a C/D racer then think about the other springs. :thumbsup:

  • ace402

Posted August 26, 2008 - 05:36 PM


Thanks for the advice!!

Related Content


Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

Wilson the Blue Privateer by jetfuel

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride

Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies

Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017

James Stewart back on a YZ450F by YamaLink

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.