HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
mightymouse291

01 yz426 fork oil specs

15 posts in this topic

hey there guys...I need to know the amount of fork oil to put into my 01 426. I am going to try Grayracer's recommended Mobil 1 Syn.

Also, which is better..to loosen top cap first, or to go through bottom of fork.

Please help me out....

Share this post


Link to post
Share on other sites

To properly change the fork oil, you need to remove them from the clamps and pump out the oil from the dampers. There isn't a drain plug as there was long ago, so this is the only way to do the job. Further, when changing fluid types it's necessary to partially fill the fork with the new fluid type, work it through, and pump out as much of the mixed fluid as you can. The 46mm fork takes just less than a quart to fill it the 100mm level, so buy one to flush with, and one to fill.

Share this post


Link to post
Share on other sites

I know the stock measurement in my 03' yz450f is 135mm from top of outer tube fully compressed. I think the range is 80mm to 150mm. I wish I had it that easy(changing fluid only). Usually if I have to get into my forks, its to change fork seals which requires more time(and money). Only "loosen" caps before removing forks from clamps. Have fun stroking your fork!lol

Share this post


Link to post
Share on other sites

thanks for the help guys. I tried to loosen the caps while in the clamps, and it wouldn't budge...I guess over torqued. I have to change the seals which blew out on my first ride on the used bike. Anyway I will pump them out, fill a little, pump them out, then fill again....100mm from the top of the tube right?

Share this post


Link to post
Share on other sites
I tried to loosen the caps while in the clamps, and it wouldn't budge...I guess over torqued.
Loosen the upper clamp pinch bolts before attempting to loosen the clamp. The triple clamp compresses the walls of the uppere tube down on the caps, locking them in place.

The oil level is a range, 85-135mm from the top of the collapsed fork assembly with the damper fully compressed, and the spring removed. Higher oil= harsher ride, but less bottoming. Lower = more supple action, but bottoms more easily. Start at about 100mm and go from there.

Share this post


Link to post
Share on other sites

I would only add ...not to battle or dissagree with greyracer...to completely dissassmble the forks and flush them out first with a cleaner/preferably contact cleaner/parts cleaner. I remove the springs, the rod, the seals, all valves and dissassemble down to each tube. Here is the problem if you do not do this at some point...The compression valve at the bottom will hold a lot of contaminants/sludge that accumulates over time.. I completely remove this valve on every fork service as well as take this oppty to replace fork seals with new. It will be impossible to get all contaminated / old fluid out without doing this procedure. It does however take more time but it in my opinion the correct way to service forks. I do it every 3-6mos depending on how much riding I do. Front and rear. It will however teach a newby how the forks and the shock really work and will educate a novice on valving tweeking.... On 426's I start with oil level at 90mm and add in 5cc increments as needed (at the track)on stock KYB 's except on my own Enzo suspension Subtank set up...oil level for that is at 70mm. :D

Share this post


Link to post
Share on other sites
I would only add ...not to battle or dissagree with greyracer...to completely dissassmble the forks and flush them out first with a cleaner/preferably contact cleaner/parts cleaner. I remove the springs, the rod, the seals, all valves and dissassemble down to each tube. Here is the problem if you do not do this at some point...The compression valve at the bottom will hold a lot of contaminants/sludge that accumulates over time.. I completely remove this valve on every fork service as well as take this oppty to replace fork seals with new. It will be impossible to get all contaminated / old fluid out without doing this procedure. It does however take more time but it in my opinion the correct way to service forks. I do it every 3-6mos depending on how much riding I do. Front and rear. It will however teach a newby how the forks and the shock really work and will educate a novice on valving tweeking.... On 426's I start with oil level at 90mm and add in 5cc increments as needed (at the track)on stock KYB 's except on my own Enzo suspension Subtank set up...oil level for that is at 70mm. :D

I would strongly recommend against general recommendations of putting any type of solvent in the forks at all. Not knowing the specific solvent you're dealing with could destroy your seals, and contaminate the oil.

Share this post


Link to post
Share on other sites

He was talking about a set of forks that would be rather completely disassembled, washed and dried. I don't see the problem.

Share this post


Link to post
Share on other sites

I sent my forks to Factory Connection for a revalve. When I got them back it shows 140mm for the oil level. Is that how much they added or is that 140mm from the top of the tube? I have not ridden it yet to see how they feel, but that sounds like a high level compared to several of the other posts I have read.

Share this post


Link to post
Share on other sites

Actually 140mm is below the recommended the range set..... 130mm is standard. You have to remember that Your filling from the top. The smaller the number the more oil is in the forks.

Share this post


Link to post
Share on other sites
He was talking about a set of forks that would be rather completely disassembled, washed and dried. I don't see the problem.

Thanks GreyRacer - that is what I mean. For complete dissassembly - Solvents are ok - just completely clean and dry.

I know several that will do this type of service once a year and just replace fluid per GreyRacers explanation every 3mo....either way you assure yourself better suspension performance with new fluid. :D

Also 140mm oil level....please check this again - has to be a mistake unless rider is 90lbs... :D

Share this post


Link to post
Share on other sites

I am in the middle of the job right now. It all came back to me once I get into them, except these are upside sown from my old suzuki forks..Anyways wish me luck reassembling......

a 1 1/2" PVC coupling fits right on for a seal driver, just cut a groove out to go around inner tube and you are in.

Share this post


Link to post
Share on other sites

Also 140mm oil level....please check this again - has to be a mistake unless rider is 90lbs... :D

I called Steve Ross w/Factory Connection in Rochester NH about the fork fluid level. He said that for Trail/Enduro/Mountains, it isn't uncommon for them to go to as low as 145mm on the '01 forks and rarely get over 125mm. These are base line starting levels based on specific data they have collected over the years depending on terrain, weight and skill level. Some fluid may have to be added, but it's easier to add than to remove. I won't get to ride until next weekend, I'll give a report on what I think.

Share this post


Link to post
Share on other sites

Okay do I leave the outer tube extended or compress it down to the inner tube to measure the oil level? I had it down and am at the top of the tubes. the owners manual called for 578 cc, but i am only at 425cc right now... any help?

Share this post


Link to post
Share on other sites

Just had mine redone with Race Tech gold valves. On my '02 YZ426, they recommended changing the stock spring from .46 to a .44 and 90mm oil. Setting is for trails at beginner/intermediate level standard stiffness. I weigh 180lbs. Not sure how that translates with the stock valves.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0