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brennan duncan

Fork Oil level for 06 yz250f

12 posts in this topic

What oil quantity is working best for the riders in the 190 lb range in the outer tubes. The forks are stock and the use is primarily motocross. I know the owners manual says 335 ml with a range of 300-380 ml---but I have noticed other suspension websites that recommend 260-280 ml. With the conflicting info I am not sure who to believe. Furthermore, when I changed the oil and refilled with the "stock" level of 335 ml I noticed a mid-stroke harshness that was not present before the oil change. I was able to reduce the harshness by changing the compression damping clicker from 12 out to 17 out. Now I am not sure if I made a mistake somewhere else during the oil change process or if I just put in too much oil. Any suggestions?

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Check with JC, but 3 out on the damper is pretty tight, your springs are going to take longer to bounce back over whoops - not good...

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I have not measured the oil level from the top of the outer tube with the fork fully collapsed-like I did with the single chamber type forks. All of the instructions I have read pertaining to the twin chamber fork design state that setting the oil level in the outer chamber is accomplished by measuring the quantity of oil poured into the chamber. Also, I have not seen any specs stating the amount of air space that should be in the fork. :crazy:

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Your manual tells the correct volumes, don't believe what you're reading on some of the websites b/c they might have something mixed around. I did some work on a guy's 07 YZ250 forks this summer and the volume I replaced with was 350cc.

To your mid stroke harshness (or maybe a spike?).... Can you tell if the fork is blowing thru the first 1/2 or so of the travel? Does the fork fall thru the travel fairly easy (or more easily than previous?)? If so, then maybe you didn't get the inner chamber bleeding quite correct, such as maybe some air in the chamber. Or, if the fork is holding up in the travel, perhaps the replacement fluid is thicker than the original fluid.

Also, check for proper fork tube alignment. Out of aligned tubes can cause sticky action.

Hope this helps.

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I was going to say measure the air space to see if there is the same level of fluid in both sides. Are your clamps maybee too tight?

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I measured the fork oil that I drained out just to verify that I refilled with the proper level and I measured 320 ml in each fork. I also cleaned, lubricated and torqued the clamp bolts to 17 ft-lbs on the upper and 14 ft-lbs on the lower. I also aligned the fork tubes before performing the final torque on the axle pinch bolts. Thanks for the suggestions though. The only thing I have found wrong is I used mobil 1 synthetic ATF in the outer chamber and when I drained the inner chamber there was ATF in the inner chamber. Maybe this contamination made the oil thicker than it should be :crazy:

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Your manual tells the correct volumes, don't believe what you're reading on some of the websites b/c they might have something mixed around. I did some work on a guy's 07 YZ250 forks this summer and the volume I replaced with was 350cc.

To your mid stroke harshness (or maybe a spike?).... Can you tell if the fork is blowing thru the first 1/2 or so of the travel? Does the fork fall thru the travel fairly easy (or more easily than previous?)? If so, then maybe you didn't get the inner chamber bleeding quite correct, such as maybe some air in the chamber. Or, if the fork is holding up in the travel, perhaps the replacement fluid is thicker than the original fluid.

Also, check for proper fork tube alignment. Out of aligned tubes can cause sticky action.

Hope this helps.

Actually, the '06 manual is incorrect. If you look in the front for fork oil volume it gives about 17oz, if you go to the tuning section it calls for 10 to 11 oz. I do not have the exact measurements in front of me but after hurting my daughter's wrists after replacing the oil I finally caught it.

Rich

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Actually, the '06 manual is incorrect. If you look in the front for fork oil volume it gives about 17oz, if you go to the tuning section it calls for 10 to 11 oz. I do not have the exact measurements in front of me but after hurting my daughter's wrists after replacing the oil I finally caught it.

Rich

I stand corrected. :crazy:

I was going on the thought that 06 and 07 forks are similar construction. The 05 uses less fluid, but those are different construction.

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The manual says that there should be 195cubic centimeters(6.59oz) in the inner/top chamber, and for the outer/lower chamber ,300cc -375cc(10.1-12.8oz) and 340cc is the standard amount, or 11.5oz.

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