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quick question fellas. how much fork oil

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the local bike shop here in town is closing it's doors and are getting rid of everything they have left so all of their inventory is being sold dirt cheap. I picked up some fork oil and gear oil and gonna go back tomorrow to see if I can get some other parts for my old beast I'm building. I wanted to ask you all if you knew off the top of your heads how much fork oil per tube an old 93 cr takes. the seals are not leaking but I would like to change the oil out at least and want to get it while it's cheap so want to make sure I get enough. I picked up 1 bottle of 15wt bel ray today just wanted to see so I know I'll have enough

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Premeasuring a volume of fluid and then pouring it inside the fork chamber is more applicable to the twin chamber showa forks. This volume amount is 325-375cc's depending on how soft or stiff the forks need to be before bottoming out. But I think your '91 forks are open chamber forks.

A way to know whether you have OPEN chamber vs. twin chamber fork is this: OPEN CHAMBER has the compression clickers at the bottom of the fork. TWIN CHAMBER is the opposite, w/ the comp clicker at the top of fork.

TO measure the right amount of fork oil for open chamber forks , you use a ruler of some kind and measure how far below the surface of the oil is from the top of the fork- WITH THE FORK IS FULLY COMPRESSED. WHere the fluid level is low, this increase the air chamber volume, therefore the forks will bottom out easier. WIth fluid level raised higher, this decreases the air chamber volume, and the forks won't bottom out as easily. The trick is to find the right amount of air chamber to allow the forks to stroke through and use up as much fork travel as possible without bottoming out all the time. I would try something like 100mm air chamber for motocross, and 150mm air chamber for rocks and technical riding. 130mm air column would be decent for general offroading.

Another thing....5w oil is the standard viscosity for all upside down forks,with some pro racers using no thicker than 7.5w for the USD forks. YOur forks being the upside down forks won't work very well with 15w oil, which is more applicable for conventional / right side up forks. Also, I think you'll need more than a bottle, closer to 1.5 bottles, to fill up two forks.

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great answer man thanks a bunch

I won't be doing any moto stuff or racing just woods and trail riding for ms so I'll go in the middle

I'll check and see if they have some 5 St oil I almost got some there but thought it might be too light I'll have to look tomorrow and see if they still have it

I'll check on where the comp clockers are tonight when I get to the house and see if they are open or twin chambers

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15 wt is heavy oil. I would go back and see if they have some 3-5wt. a 32 oz bottle will be more than enough...but not sure what they sold you. The older KYB were open chamber and you should set the volume by height in the leg collapsed with spring removed. probably around 130-150mm air gap....more fluid equal stiffer. Look around in here....there are some pdf manuals listed.

editted. should have read jeds entire post ..looks like he covered it.

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Isn't Bel-Ray a little notorious for causing fork seal leaks? I love Bel-Ray for the waterproof bearing grease :smirk: , but I've always been told to stay away from the fork oil. Maybe someone else will chime in with some actual experience with their fork oils.

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