RPM fork valve and spring fitting

[balky1]

Take a half full bottle of water and hold it with your thumb and index finger in the middle of the bottle at the water line.

Now, tilt the bottle.  What do you see?  Until you get to extreme angles, the level of the water from the top of the bottle will pivot at the center of the bottle and remains the same for a wide range of angles.

The forks are only slightly tilted and narrow so measuring the level will be perfectly fine with them installed.  This is definitely not rocket science.

Show is about to start.   

[Country Joe]

 

[Pat Conlon]

If you take the forks off, you now also have the ability to repack the front wheel bearings....

....see Pat run for cover.........

[FJ1100mjk]

Take a half full bottle of water and hold it with your thumb and index finger in the middle of the bottle at the water line.

Now, tilt the bottle.  What do you see?  Until you get to extreme angles, the level of the water from the top of the bottle will pivot at the center of the bottle and remains the same for a wide range of angles.

The forks are only slightly tilted and narrow so measuring the level will be perfectly fine with them installed.  This is definitely not rocket science.

Just trying something here...

Using an estimated fork tube ID of 39mm, and the rake angle of 27 degrees, it appears the level of fork oil from one side of the fork tube to the other differs close to 18mm.

[FJ_Hooligan]

Yes, but the level is ~9mm too high on the back side and ~9mm too low on the forward side.  Drop the tape measure in the middle of the tube and you'll get it close enough.  You can do this same thing with carb fuel level as long as you make the measurement in the middle of the float bowl.

Or, go ahead and spend 3 more hours to pull everything apart.  I'm just trying to help.

That's also why whenever I read the advice that the proper fork oil level is measured without the spring and the tube fully collapsed I always recommend to make a second measurement with the spring in place and the fork fully extended.  That way when you only want to change fork oil, you can do it without disassembling the entire front end just to collapse the fork.  Saves LOTS of time when you just want to get fresh oil in the fork.

But it's just advice.  Feel free to ignore it.

[FJ_Hooligan]

Also, your math doesn't look correct. 

I get tan(27*)x39mm = 19.87mm

:-)

[Pat Conlon]

Geeze Louise, along with measuring the oil level at an angle, you expect me to accurately measure the oil level with the spring in the tube?

"A man's got to know his limitations" and I am not that competent........ besides, I can r/r both forks, change the fluid in under an hour.

I've got one of these Motion Pro goodies and it works a treat (with the springs out)



http://rpmracingca.com/proddetail.asp?prod=tools%3AForkLevel

[racerrad8]

Don't you have to divide by two since the center line of the fork should still be the proper level...?

When we change fork oil on the bike, it us the fork level tool at the middle/center line of the side of the fork tube.

We will have to check the difference in oil level for perpendicular to rake angle on the next set we rebuild.

We only use this fork level tool: http://rpmracingca.com/proddetail.asp?prod=tools%3AForkLevel

Randy - RPM

[FJ1100mjk]

Also, your math doesn't look correct. 

I get tan(27*)x39mm = 19.87mm

:-)

Neither does yours. Your formula is incorrect. It yields -127.6

Next time you attempt Trigonometry like you did above, convert degrees to radians, and you'll get the correct answer.

39 X TAN ((27/(180/π)) = 19.87

The 17.61mm dimension shown in the graphics above, is not based on the Tangent function. It is a correct value.

You assumed that longer leg of the triangle is perpendicular to the line representing fork tube. It is not. Look closer.

[FJ_Hooligan]

Wow, really?  This is almost embarrassing.

I don't know what calculator you're using, but with my calculator we apparently get the same answer.  Or did you miss that above?

If you want to get pissy about it maybe you need a new calculator or lessons in using one.

In degree mode, tan(27*) gives the same answer as tan(27*pi/180) in radian mode.  But since I have to explain this then I'm probably wasting both of our time.

My formula is correct.  The legs of the right triangle are the 39mm ID and the far side of the fork tube and tangent is opposite over adjacent.

Where did you learn your trig?

[FJ_Hooligan]

Randy,
What you're doing is correct, the level at the centerline of the fork does not change.  That was my original message.

You can change my fork oil anytime!

[FJ_Hooligan]

Geeze Louise, along with measuring the oil level at an angle, you expect me to accurately measure the oil level with the spring in the tube?

"A man's got to know his limitations" and I am not that competent........ besides, I can r/r both forks, change the fluid in under an hour.

Pat,
Correct me if I'm wrong.  But don't you HAVE to remove USD forks to drain the oil?  There is no drain screw on the bottom of the fork?

I'm just trying to save everyone an extra shot at cracking/breaking the fender tabs.

DavidR.

[FJ_Hooligan]

On second thought, NEVERMIND!  Maybe I shouldn't try to help.

Everyone please ignore the advice I gave above.

EVERY time you want to change your fork oil, pull the entire front end of your FJ apart so you can accurately measure the oil level in an upright position.  Good luck not cracking any fender tabs.

In the meantime, I'll have the job done as practically an afterthought.

I really didn't think it was a  thread, but I guess I was wrong on that too.

[Pat Conlon]

I'm gettin a wee bit antsy.....is it rally time yet?

[Mike Ramos]

I'm gettin a wee bit antsy.....is it rally time yet?

Hmmm, Mr. C. - perhaps we can get started early? 

I'll bring the booze & you bring the babes...?

Just a thought...