Fork oil quantity

[Jclevesque]

Getting ready to do a full fork rebuild and spring replacement. Gonna buy 10wt Belray oil and just looked at quantity and showing near 17oz of oil per fork. Is this correct? This will be my first time doing forks on the Roadstar. Just want to ensure I got at least 2 quarts of oil before I start. JC

[Lug Nut]

Clean forks thoroughly (remove from bike)... I use brake cleaner first to get nastiest shit out. Then fill each fork halfway Auth ATF and cap it (all internal parts removed and can clean those with brake cleaner) and shake back and forth a ton on each fork.... Then let drain... Then quick rinse with brake cleaner.... Then they should be clean and dry.... May want to look at plastic bushing and all seals... Cheap to buy and not a hard job....

You can measure fork oil from top... I think mine were to be 110mm or something like that. . I did that instead of measuring oz.

[roadiemort]

Saved from a post.

[Jclevesque]

Yeah I saw in the manual when fork tube fully lowered without spring 110mm to top. Quantity was a bit over 16.x oz or so. I have a leftover jug of Belray (20oz or so) from the last rebuild of my XS 650. Just want to confirm that close to 2 quarts of fork oil is required. And yes I am doing a full rebuild with all seals and bushings.

[Brad_G]

16oz is a pint (32oz = quart) so if you have some leftover from your other rebuild you'd only need a quart.

[jd750ace]

It’s a tad over a quart to do 110mm from the top.

[Jclevesque]

Right on guys thanks!

[Brad_G]

jd750ace can I ask a question (and it may sound dumb because I've never been inside forks)? I'm curious why it takes over 2 quarts. According to the service manual:

Quantity
554.0 cm3 (18.73 US oz) (19.54 Imp.oz)
Recommended oil Yamaha fork oil 5WT

So if a quart is 32oz, that's roughly 13oz more than the manual states. Is there a difference in the internal springs and parts you're using where it requires more oil to fill the volume of the stock parts that are exchanged? The manual mentions the 110mm height as well. Just trying to wrap my head around why there are differences here.

Thanks for enlightening the uninformed.

[Jclevesque]

His number is for both forks at 110mm. Your quantity noted from the manual is each fork leg.

[Brad_G]

Yeah I figured the manual was giving a per fork measure. But above he mentions just over 2 quarts which would be 64+oz.

One quart is almost 40% more per shock than the 18.73oz stated in the manual. Watching his video I know he's not spilling it all over the floor while he's working. So I'm just trying to understand why as I'll eventually need to go in there.

[jd750ace]

I said it wrong. You’ll need 2 quarts on hand because it takes a little over one quart to hit the mark on both tubes. There is nothing in the tubes when you set up the oil height, so the displacement from the springs and spacers doesn’t come into play.

[Brad_G]

Thanks for the clarification JD. I wasn't trying to be an ass but was confused. That makes total sense and jives with what the service manual states. I just wasn't sure if this were another case of where the service manual may have had a misprint.

[jd750ace]

No worries. Good catch. People have been known to put about half the required quantity in each tube, then put 4 ounces of HD30 oil in the bottle and shake it up to make up the small amount more required. I feel like this the same as I do about trying to blend 5 and 10 weight in a cup to make 7.5. That’s not exactly how it works, but I also understand how it feels to use 2 ounces out of a 12 dollar bottle of fork oil .
I don’t worry about it Because I have 2 sets of forks that use the same oil.