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Discussion Starter · #1 ·
Mates,

I have problem with my old faithful RS Pike Race - I rebuilt it with all new o-rings and Enduro seal kit. Now the compression travel is very stiff, as the fork had an overly firm spring in there. I studied the problem by removing the coil spring, and found out that the fork popped back up a bit even without the coil! I opened the bottom bolt in the other lower leg a bit, and and some air farted out of there...

So to me it seems that there is an unwanted air chamber in at least one of the lower legs. How are the lowers supposed to ventilate anyway? Otherwise the rebuild seems fine, no leaking and the oil level in the damper is correct too...

Any ideas how to get rid of this additional air spring in my coil fork?

Thanks!
 

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Sandels said:
Mates,

I have problem with my old faithful RS Pike Race - I rebuilt it with all new o-rings and Enduro seal kit. Now the compression travel is very stiff, as the fork had an overly firm spring in there. I studied the problem by removing the coil spring, and found out that the fork popped back up a bit even without the coil! I opened the bottom bolt in the other lower leg a bit, and and some air farted out of there...

So to me it seems that there is an unwanted air chamber in at least one of the lower legs. How are the lowers supposed to ventilate anyway? Otherwise the rebuild seems fine, no leaking and the oil level in the damper is correct too...

Any ideas how to get rid of this additional air spring in my coil fork?

Thanks!
Something doesn't sound right. Air pressure just doesn't enter the lowers. Maybe the seal between the damper and lowers isn't doing its job. I'd see if the damper side lowers are filling w/ oil .
 

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Discussion Starter · #3 ·
I already checked the oil level in the damper and it was correct. Apparently the space in the lower leg below the damper is closed, even though in my opinion it should breathe somehow to compensate the change in the volume when the fork travels in and out?
 

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That is weird, I have never had air pressure build up in the lowers (I have an `05 Pike). At least nothing significant enough that I noticed air escaping when I pulled the lower bolt out.
 

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Sandels said:
Apparently the space in the lower leg below the damper is closed, even though in my opinion it should breathe somehow to compensate the change in the volume when the fork travels in and out?
Any decent fork is build this way MTB, moto, etc. If they were open as you suggest, the oil would pour out if inverted (if you crashed) and you would constantly be pulling dirt into the system as the fork breathed (very bad..see here http://forums.mtbr.com/showpost.php?p=7825134&postcount=1 )
Some moto forks use an air bleed screw, or use a volume expansion chamber to decrease spring affect, but this has more to do with temp changes due to long ride times and 'work' being done on a moto fork that MTB forks do not normally experience.

The air spring affect you are feeling is pretty minimal compared to spring force, but if you are running a very light spring (and depending on the volume change of the trapped air) you might feel a slight diference by doing the following:

Turn the fork over (bike on bars/seat or similar).
Crack the footbolts on the fork (on a RS, you need to tap the bolts 'into' the fork to relase the press-fit of the inner shaft)
Compress the fork as far as possible (get someone to help, or compression strap between the crown and brake arch if needed).
Tighten the footbolts while the fork is compressed...
 
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