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KTM Fork Oil Amount Question

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'11 KTM 250xc

Just want to make sure I understand something.  On my forks KTM calls for 365ml of oil.  My forks have been serviced by a suspension shop and they installed 250ml of oil.  Question is, why didn't they put the recommended KTM amount in them?  Does less oil give the forks more air inside to make them more plush.  Wondering why they would do that.  I'm going to service them myself this time and just making the decision on the amount I will put in this time and what effects it will have.  Thanks.

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If u liked the feel of what your tuner done for you use his oil volume.

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It's good but could it be better?  I have since moved and ride a different type of terrain. 

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See what the spec is for the air level (top of the oil to the top of the fork) should be.  Pull your forks, take the springs out, collapse everything and measure it to see if it is within spec.  If not, add or subtract fork oil to get it where it's supposed to be.  Lots of YouTube videos on how to do this.

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If they really only put 2/3 of the oil specified in there, tire's a good chance the cartridge isn't submerged, and a lot of air is being pushed around in the system, causing a lot of cavitation, and you may be relying only on the spring for suspension.  

If you do check the level and find you have to add a lot of oil, be sure to bleed the system to get the air out.  You can see how easy it is to do this in this video.  Start watch at 22:55.

 

I know this probably isn't your shock, but the process is the same.  You don't need the fancy syringe, just make a mark on a stick at the level you want, and other marks 10mm on either side of this mark.  Put a little oil in, check the level.  If not enough, put a little more in.  Keep doing this until you have it set at your mark.  The syringe is easier, you can just overfill a little, set the depth on the brass tube, and suck out the extra until the syringe starts bubbling and you're done.  I made one with a syringe, brass tube that I slid in the end and shrunk some heat shrink over the joint.  I used a tie-wrap around the brass tube that I can slide up and down to set the level.

Pulling the forks to do this is pretty simple.  Takes me only about 5 minutes to entirely remove the front wheel and both forks.  Takes me maybe 15 minutes to take the cap and spring off and set the level and reassemble each fork leg.  Then another 15-20 minutes to put it all back together.  Be sure to clean off any oil on the upper fork tube where it gets clamped into the triple clamps.

 

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Those are a different type of fork. Mine are closed chamber forks and you add oil by volume and not by oil height. 

 

 

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Probably too late, but don't use volume, measure the oil height, a lot more accurate.

pull your springs and measure whats there from top of the tube with fork collapsed.

a cap full of oil can mean the difference between a fork that works right and one that doesn't.

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14 hours ago, Spud786 said:

Probably too late, but don't use volume, measure the oil height, a lot more accurate.

pull your springs and measure whats there from top of the tube with fork collapsed.

a cap full of oil can mean the difference between a fork that works right and one that doesn't.

Not on the cc fork.  factory fill on them for the xc bike is 365 cc, many tuners may use less...BUT 250 is not enough.

This is for the outer chamber, the inner is a different story.

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2 hours ago, E-TECH said:

Not on the cc fork.  factory fill on them for the xc bike is 365 cc, many tuners may use less...BUT 250 is not enough.

This is for the outer chamber, the inner is a different story.

Yeah I couldn't tell by the year, if it was open chamber

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Had a tuner do that to my forks. manual said 353 min. to 425 max. , when I changed fork springs and dumped the oil out there was only 250 cc in there ? what the hay. And right on the sticker that the tuner put on your fork , it said 370 cc ? Just have to wonder sometimes what are they doing. Lucky that I had to change springs after two riders , or I would have not known for a month or two.

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 I don't think that if I drain them for a week more than i did,  that a 100 more cc`s would come out lol. I do read my manual , and used a ratio rite.

Edited by tjg53
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