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
therapture

426 fork oil spec?

14 posts in this topic

What weight fork oil is spec'ed for the '00 426? I am stuck at work, going to have the wife unit pick up my seals and oil so I can change my busted one. My local shop carries BelRay fork oil. I would *assume* like SS7 or a 7 weight oil, seems most modern bikes used that spec, at least back in 97 when i had stopped racing.

Share this post


Link to post
Share on other sites

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:<HR>Originally posted by john.hilton@cape.k12.de.u:

I just did the forks in my 01 426, they come stock with 5wt. You will need about 20 oz per tube.

John

Thank you sir, now I can have the wife pick up the parts without depending on the moronic parts person at the said shop to determine what weight...LOL...

Share this post


Link to post
Share on other sites

Mobil 1 ATF works great! Its right around 7 wt. and it seems to make the seals last. We use a blended version of Mobil 1 ATF in all of our fork rebuid and revalves, up to now I have only had 1 fork seal leak, that was less than a 1% failure rate.!! It increases the damping action of your fork and it also increases the range of adjustment from your clickers.

Just make sure to do a complete teardown and remove all of the old oil and sludge. Email me if you need a complete procedure, I posted it somewhere around this sight.

If you take apart any new KTM forks, you will find a fluid that looks, feels, and smells remarkably like Mobil 1 ATF!!!

Good Luck, John

Share this post


Link to post
Share on other sites

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:<HR>Originally posted by John Curea:

Mobil 1 ATF works great! Its right around 7 wt. and it seems to make the seals last. We use a blended version of Mobil 1 ATF in all of our fork rebuid and revalves, up to now I have only had 1 fork seal leak, that was less than a 1% failure rate.!! It increases the damping action of your fork and it also increases the range of adjustment from your clickers.

Just make sure to do a complete teardown and remove all of the old oil and sludge. Email me if you need a complete procedure, I posted it somewhere around this sight.

If you take apart any new KTM forks, you will find a fluid that looks, feels, and smells remarkably like Mobil 1 ATF!!!

Good Luck, John

Thanks for the heads up, I might try that stuff if this is not better. I have been working on bikes for @12years, so a fork teardown is old hat...I used the Belray 5wt....hope it is equivalent to stock, and I also found my oil level was WAY down there, closer to the standard setting of 130mm even after I added 15cc to each tube at the track last weekend.

Considering my large size, height, and weight, not to mention I love jumping, I set my oil level at 85mm, wich is only 5mm from the minimum level. That SHOULD make a major resistance to bottoming.

Share this post


Link to post
Share on other sites

no no no its 200oz per tube :) yeah thats it!

well at least it would help your bottoming prob

What shop Dale's or Bosarts?

You gonna make it sunday?

Share this post


Link to post
Share on other sites

The ATF trick isn't all it's chalked upto be unless you revalve to compensate for the thicker oil. It will alter the damping characteristics, and not necessarily for the better.

Share this post


Link to post
Share on other sites

I'm not a pro suspension guy by any means, but intuitively it seems like a thicker oil (7.5 vs 5wt) would make the fork somewhat slower, or in other words feel harsher on square edge bumps and the like (assuming all other things equal). Can anyone conform or deny this?

Share this post


Link to post
Share on other sites

This is a good topic !

I would have scoffed a couple years ago at the idea of using transmission fluid in forks.

I think we as consumers get in a kind of "packaging mindset" if you will....just because an item is labeled to be used specifically for a certain type of application, we tend to stick to the packaging label....

If Mobil 1 ATF was packaged as fork fluid and all of the POSITIVE testamonials from suspension tuners and riders were advertised, I guarentee we wouldnt give it a second thought....

But as consumers we get skeptical when something is used for other than its advertised purpose....

Tuner,

Go ahead and set up 2 bikes (especially YZs) with stock forks. Use Mobil 1 ATF in 1 bike and a 5wt "packaged" fork oil in the other. Set the clickers on the Mobil bike 2 softer, and see if you and any average rider can "feel" anything different between the 2wt difference of the fluids...I've done this, the results might suprise you. The 2wt difference doesnt require a revalve.

I am not saying that in all suspension applications, it is ok to use Mobil. Especially dont use it in the PDS shock, there will be an issue where the more viscious fluid will hamper performance.

I will leave you with another question to keep this thread moving..

What is the main complaint of the average rider with his YZ suspension...?? Think about this question and how a different fluid might affect performance..

Take Care, John

Its 9:45 friday night and I am building suspension :)

Share this post


Link to post
Share on other sites

Funny, at 9:45, I was doing the exact same thing.

The complaints you (well, me specifically) get from YZ owners vary totally from one rider to the next. A lot depends on how good of suspension they've ridden on before. If a guy rides CR's all his life and jumps on a stock YZ, he'll have virtually no complaints. The YZ I was doing last night is for a guy who rides woods almost exclusively. So he's getting the Barc-a-lounger valving. I'll be doing the best part tomorrow- the test ride.

I agree 100% about the perception of a products advertised and intended uses. I use ATF in two stroke gearboxes occasionally. Some guys cringe at the tought of not using a motorcycle specific oil. They think the "shear loads" on a two stroke gearbox far outweigh the loads palced in an automotive environment. Mom's Buick station wagon pulling the boat generate so much more stress on a fluid than a dirtbike gearbox, not to mention that there are quite a few cars using ATF in their manual gearboxes as the factory recommended lubricant. so, I don't dismiss the Mobil 1 ATF due to the fact it is ATF but it isn't the weight I want to pour in any of the forks I work on- simple as that. I may give it a try sometime when I'm feeling froggy, but not right at the moment. I put way too much emphasis on plushness to go to a thicker oil. Turning two clicks softer will only help the low speed damping, not hte high speed hits where the plushness is achieved (or given up).

Share this post


Link to post
Share on other sites

Tuner

You say that thicker fluid hampers high speed damping?

Lets go back to fluid dynamics...(we are talking basic textbook stuff), A piston and a shim stack is nothing more than what..? It is a variable metering orifice, plain and simple.

The larger the ports are in that orifice, the LESS viscosity affects performance. The stock ports are pretty large and even more so are the race tech valves.

Also(now this is really important) what type of situation opens the valving more..? low or high speed..? I am sure we agree that a high speed hit opens the valving more, with the valving opening more, as we stated above , fluid viscosity plays less (because the orifice is opened more during a highspeed situation)into the picture than at low speed.....sooo as we factor in basic fluid dynamics, viscosity has a bigger impact on a low speed situation, where the valving is opened less than at a high speed hit...!!

Its all very elementary my dear Watson...!!

Share this post


Link to post
Share on other sites

No question the shims open more with a high speed hit. But does it make the viscosity difference moot? Personally, I don't think so. Sure, you can valve around either oil but virtually all my experience is with the 5wt.

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