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CaptainKnobby

Adjusting fork oil level?

10 posts in this topic

I was just wondering if you can adjust the fork oil level in the forks without having to remove the forks from the bike? I have seen in my 06 yz450f's service manual in the back of the book on adjusting the front forks........For example!..... It says in the book if the front fork is obtrusive (I believe thats the word they used) tending to raise your posture, decrease the oil amount in 5mm increments. Can you do this without haveing to take the forks off the bike and can you add oil with out having to. Sounds like it would be alot of work to just add or decrease 5mm of oil in the forks if you had to take them off the bike and wouldnt be worth the trouble.:thumbsup:

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You can loosen the top and bottom triple clamp bolts, remove the handlebar from the bike, and slide the forks up untill they go past the handlebar clamps so that you can use the fork cap removal tool to unscrew the fork caps. Then add the oil. Adding oil will improve bottoming resistance. If you want to remove oil, you will need a syringe with measurements on it, simply remove the exact amount of oil on both forks.

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Oh one other thing, once you get the forks to slide up enough to where there is enough clearance for you to unscrew the fork caps, re-tighten the triple clamp bolts so the forks don't spin in the clamps, then unscrew the caps.

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You can loosen the top and bottom triple clamp bolts, remove the handlebar from the bike, and slide the forks up untill they go past the handlebar clamps so that you can use the fork cap removal tool to unscrew the fork caps.

If you remove the bars by removing the handlebar mounts from the clamps;

> You will only have to remove two bolts instead of 4

> You won't have to raise the forks (you will need to loosen the top clamp pinch bolts to loosen the "caps")

> and you won't have to reset the postion of you bars when you go back together

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you can use the fork cap removal tool to unscrew the fork caps.

What is this "fork cap removal tool" you people speak of? I need to do a fork oil change but my biggest shifter spanner isn't even big enough to crack the caps open(3mm too small). What does everyone else use to get they're caps off, a bigger shifter?

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What is this "fork cap removal tool" you people speak of? I need to do a fork oil change but my biggest shifter spanner isn't even big enough to crack the caps open(3mm too small). What does everyone else use to get they're caps off, a bigger shifter?
You need the wrench (spanner to you, mate) for removing the damper (what you think is the fork cap):

http://www.motionpro.com/motorcycle/tools/fork_cap_wrench/

(actual size should be 49mm, but the 50 works)

...and the base valve removal tool:

http://www.motionpro.com/motorcycle/tools/fork_compression_valve_removal_tool/

..to open the cartridge and drain/refill it.

The fork seals don't need to be disturbed for this operation, but you may as well change them. If you have a seal driver for an '04 YZF, it works. Use MSR -HP seals for an '04-'05, or the OEM seal for an '04, with a new set of wipers.

You won't find Yamaha S1 oil anywhere for less then an arm and a leg, and frankly, it's not that good. I use Maxima Light Shock Fluid (3wt), but you can use ant good suspension oil in the 2.5-5wt range.

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Thanks for the info and links Gray! Can just the base valve be removed to change the oil? I've actually had some fork oil on the shelf for a while, I didn't know that I wouldn't be able to get the fork cap(and base valve) off!

I'll probably put off changing the seals until they blow(and see how long they'll actually last). My right side seal (for some strange reason) started leaking when my bike was tied down really hard by some other guys to a trailer on a ride I did last year. There must've been some dirt caught in there somewhere 'cause it hasn't leaked since I did the "thin plastic under the seal" cleaning trick.

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Can just the base valve be removed to change the oil?
Nope. There are two oil chambers. Look through the procedure in the manual. The one that the base valve closes up is the damper cartridge itself. You cannot change the oil in the cartridge without removing it, because it has to be inverted to drain it, and you have to compress it completely to reassemble the base valve into it. (note that the "base" valve is also called a compression valve, and is on the top of the fork)

The outer chamber can be changed on the bike, but as I said before, it isn't really any easier to do it that way.

One word of caution if you intend to leave the seals until later: Do not let the forks extend more than 10" or so while the damper is removed. If they extend beyond their normal travel limit, the seals may be damaged by a sharp edged groove they normally never come in contact with.

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I actually posted a reply earlier but it's somehow disappeared!

I should have already taken a look in the manual but I was expecting this to be as easy as changing fork oil in my other bikes. Thanks for the caution, and I'll order some of those tools you mentioned. Cheers, Ben.

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