Two Stroke Motocross

Two Stroke Motocross Forum => Technical => Topic started by: jesse.fenner3 on August 20, 2012, 08:58:04 PM

Title: oil level on forks off a 2004 rm 250
Post by: jesse.fenner3 on August 20, 2012, 08:58:04 PM
just wanted to see how much oil these forks should have in them after rebuild thx guys
Title: oil level on forks off a 2004 rm 250
Post by: arnego2 on August 20, 2012, 09:54:20 PM
On my RM250 I use 380ml per fork leg. ATF, as I frecuently change forkoil.  :D
Title: oil level on forks off a 2004 rm 250
Post by: beaner on August 21, 2012, 08:14:14 AM
ATF in a cartridge fork?

I'll check my manual when I get home and let you know.
Title: oil level on forks off a 2004 rm 250
Post by: SachsGS on August 21, 2012, 03:16:47 PM
My friend was talking to a powersports lubricant rep once and the rep. said all fork oils are derived from automatic trans. fluids - 10 wt is type F, 2 1/2 wt Toyota etc..
Title: oil level on forks off a 2004 rm 250
Post by: arnego2 on August 21, 2012, 04:45:48 PM
That's great info, I wasn't even aware of that. I use ATF becaue it is around W7.5, easy to come by and I change the oil every 40 hours.
Also work good in trannies and the smell will give a crank seal leak away. I have a reasonable hig outside temperature so the viscosity drops down fast.
Title: oil level on forks off a 2004 rm 250
Post by: beaner on August 21, 2012, 06:48:17 PM
That's bad info because it's BS.
Even though the SAE viscosity rating system is totally inappropriate for suspension fluids, ATF would be roughly a 10-15W oil.
The real problem with the SAE system, and suspension fluids, is that one companies 5W oil may be heavier than another companies 10W oil.
I did a lot of suspension tuning on my race bike with viscosity. If you have a suspension that you're not happy with, it's the second thing you should do after springs, and you should ALWAYS pursue it before even thinking about a revalve. If I used oils based on SAE viscosity, I would never be able to tune it.
Here's a chart that shows the viscosity's in centistokes. A much more reliable way of classifying suspension fluids.

Title: oil level on forks off a 2004 rm 250
Post by: beaner on August 21, 2012, 07:07:32 PM
Quote from: jesse.fenner3 on August 21, 2012, 03:58:04 AM
just wanted to see how much oil these forks should have in them after rebuild thx guys


368 ml is the standard amount with 326-421 acceptable for tuning purposes.
Title: oil level on forks off a 2004 rm 250
Post by: SachsGS on August 22, 2012, 04:04:55 PM
This information was given to my friend by one of the chief technical reps. of one of the world's largest lubricant manufacturers while my friend was competing at the Six Days in Europe.
Title: oil level on forks off a 2004 rm 250
Post by: beaner on August 22, 2012, 07:35:28 PM
If that's the info he got, he either got some bad info, or he misunderstood what he was hearing.

Look up the MSDS sheets on ATF for all the manufacturers, and see what the viscosity's are (the one you're interested in for forks is cst @ 40C). They're almost all exactly the same. ATF will work fine as a suspension fluid, as will many other fluids, but the viscosity is inappropriate for just about anything other than some open chamber forks.
Title: oil level on forks off a 2004 rm 250
Post by: SachsGS on August 22, 2012, 10:47:20 PM
You could be right but,on the other hand, I doubt lubricant manufacturers are going to custom engineer and manufacturer something from scratch for such a small market. When the tech said "Derived from" I suspect he meant that ATF is used as a "raw material" in the manufacture of fork and shock lubricants. It would be interesting to see if there are empty 45 gallon drums of ATF behind the Belray facilities.