GS850 Fork Oil Amount

[Guest]

I'm putting some GS850 forks on my '78 GS750E. How much fork oil does each fork take? It's 180cc for the GS750's 35mm tubes but the GS850's are 37mm and have air caps. Thanks.

[bwringer]

The amount of oil is completely irrelevant.

The oil level is what's important, and it's also very important that they are the same on each side.

On these forks, set fork oil to 140mm from the top with the springs out and the forks collapsed all the way.

If you Google "fork oil level tool" you'll see what the "official" tool looks like, and it's quite easy to make one yourself from a large syringe.

You basically put in a little too much oil, pump the forks several times to make sure there aren't any air bubbles inside, measure a tube, stick it into the fork and slurp out the excess. Bingo, perfect fork oil levels every time.

Ideally, you do this with the forks off the bike and held vertically. If they're on the bike, do your best to be consistent where you place the tube.

[tkent02]

What he said, you can use a turkey baster and any stick or tube to measure the distance.
It's pretty easy to make a proper tool like this:

http://www.progressivesuspension.com/pdfs/R00799-025%20Instr%20FOL-2.pdf

Like he said, the actual amount isn't that important, but the two fork legs being the same is. Higher oil level (actually the smaller air space left above the oil) will increase the fork's resistance to bottoming.

[Steve]

Brian is right, of course, but the answer to your question is found in the service manual. You can download a manual from BassCliff's site.

The 'fun' part will be which specification you need to use. The spec for early forks is 251ml in each leg, later forks take 245ml, but the level remains the same at 140mm.

It should also be pointed out that specs are different for the "L" forks. Hopefully you have not gotten a set of them for your 750, as it will change the handling. "L" forks take 302ml of oil, and have a level spec of 160mm.

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