Last year I changed out the original fork sliders to chrome and installed new seals. I did not have the fork oil level gauge so I measured 10.8oz of fluid (what the manual calls for) with a digital scale so I made sure I had the right amount of fluid. So this year I wanted to change the fluid again this year, I know you don't need to but I had 14,000 miles last year but I like to change all the fluids. I purchased a level gauge this year and I set the gauge at 142mm and I pulled out about 2 to 3 ounces of fluid using the gauge and I weighed the fluid that came out and it was 10.4oz so I set the level gauge to the other fork that I did not drain and that came to 92mm on the scale. 10.8oz of fluid = 92mm on the fork level gauge and not 142mm.

Long story short do I put in 10.8oz or 142mm on the level gauge? One of them is not right and I wonder if it is because the FLHX has a lower suspension than the FLH. I ran all last year with 10.8oz of fluid in the forks and they seemed fine.

 

I think it's fluid ounces not the weight of the fluid

 

Interesting. I used 10.7 oz when I changed out my forks and seems ok a year later

 

They are both correct. The fl/oz measurement is a start point with just enough extra to ensure the "sucker" will contact the fluid, the linear measurement from the top of the fluid to the top of the collapsed tube is the final adjustment.

 

10.8 fluid ounces is 10.8 ounces!

 

At 10.8 ounces poured in the tube the sucker pulled out 2 to 3 ounces of fluid. Which would make around 7.8 to 8.8 ounces in the tube. I don't think you should have that low of fluid in the forks.

 

You sure about that? What is the density of the oil you are using?

 

Not true....measure liquids in a measuring cup and dry on a scale

 

My bad. I did the calculations. The specific gravity of 10W and 20W oil is between .88 to .94 and after the calculations 10.8 fluid ounces of oil = 11.38 ounces in weight. Which means that I have less oil in the forks but a mechanic told me that you can off by as much as 1 to 2 ounces and you will be fine.

 

Ditch the digital scale and the specific gravity conversion formula, and just get a cheap measuring cup with a fl/oz scale. Bottom line is the linear measurement from the top of the fluid to the top of the collapsed tube is whats critical, doesn't matter how much fluid is left after the linear measurment, or what units of measurement you use to account for what's left over.