YZ450 Fork oil/ tuning


5 replies to this topic
  • ACE_269

Posted December 25, 2005 - 08:44 PM

#1

OK well I just pulled my forks to replace the fork oil and noticed that they look either really low , or I am way off on the level needed. I always thought that about 3" was a good start but I checked mine and there isnt any oil @ 6". I think I might need to check some resources and find out exactly where it needs to be. Prolly drained out the seals w/ my luck. Anyone have any suggestions?

Plus, I looks like the forks have alot of static sag in them and might need shimmed. Just sitting on the ground, they have 4mm of play in them. Seems excessive to me.

I was reading the slick fork thread and was thinking about going the cheap route and just waxing my tubes, lol. Who knows, it might work-redneck engineering.

  • grayracer513

Posted December 25, 2005 - 09:06 PM

#2

You din't specify the year. If you're working on an '03 or '04, oil level has to be checked with the spring removed, and both the tubes and damper completely compressed. Oil level should be between 80-150mm down from the top. Lower oil level gives a plusher ride, but an '03 will foam and bottom if it's too low. Higher oil level gives the bike a harsher feel.

  • ACE_269

Posted December 25, 2005 - 09:36 PM

#3

Sorry, it's an 05 YZ450F. Just bought it this year from a guy who raced it for a year. Not sure what he has done to it or how much abuse it has been thru, so i'm trying to get it all ready for the season next year.

And yeah, I was looking at the way its assembled, trying to figure out if I could replaace the seals on my own and it looks kinda complicated to get the valving detatched from the upper tube. I had a 98 KX 250 and dooing those was a snap. Are you saying I have to take the valving apart to measure, or just unscrew the top cap from the upper tube and let the upper tube slide down to the bottom of the lower fork( the part that has the valving in it). Thats how it did my kx. Seemed hard to get my measuring stick ( zip-tie) down in the tube due to the spring getting in the way. Thanks for your help Grayracer.
Hey, have you ever heard or advancing the cam in your 450? A guy at a local shop said he would do it for me, said it would increase HP by 8hp at peak and 3 HP off idle. worth a try IMO.

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  • djo269

Posted December 26, 2005 - 12:10 AM

#4

You din't specify the year. If you're working on an '03 or '04, oil level has to be checked with the spring removed, and both the tubes and damper completely compressed. Oil level should be between 80-150mm down from the top. Lower oil level gives a plusher ride, but an '03 will foam and bottom if it's too low. Higher oil level gives the bike a harsher feel.


I have an 03' yz450. Which do u think would offer me a plusher ride? Say I have both of the stock .46 springs in with about 100mm of 5wt oil...or...say I have one stock .46 & one .52 spring in with about 135mm of 5wt oil??
I weigh close to 285lbs now during the holidays and just want to plushen the forks abit. thanks

  • grayracer513

Posted December 26, 2005 - 09:29 AM

#5

Hey, have you ever heard or advancing the cam in your 450? A guy at a local shop said he would do it for me, said it would increase HP by 8hp at peak and 3 HP off idle. worth a try IMO.

Sorry, I haven't done anything with the '05 fork. Can't help with that.


I have heard of the cams being retimed (Doug Dubach at Dr.D does this, and I think he advances the cam. Contact him), but my understanding is that his purpose in doing it is to move the power band up the RPM range to reduce the low end hit on the early models.

Bear in mind two things: when converting a WR426 to YZ timing, the cam is retarded, not advanced. when this is done, the bike has more power overall, and more top end. Secondly, if the cam is advanced, the decompression pin will need to be extended in order to hold the exhaust valve off its seat until the right point in the compression stroke.

When Dubach does his cam mod, he does so by removing the sprocket from the cam and reindexing it, and he comensates the decomp mechanism at the same time. As far as there being a gain of 8 hp, I will boldly venture that that is total BS. That's an impossibly large gain for such a minor change in the engine. Call or e-mail Dr.D an ask for more facts about what this mod will do, and what's involved in it.

  • mikedabike

Posted December 26, 2005 - 10:55 AM

#6

The 05 fork is like the Showa twin chamber design. The dampening mechanism is in a sealed cartridge in the top. You need to buy or make a the special tool to get it apart. The seals are no harder to change than any other fork. You dont have to take the dampening assembly apart to change them you simply unbolt it from the bottom and take the whole assembly out. when you reassemble them you really can't check the oil level you have to do it by volume. I beleive the capacity for the outer tube is something like 9-11 ounces. Check your manula for the exact specs. The play when fully extended is normal, the springs will actually rattle if you shke them when fully extended.





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