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Offline Kris

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Re: Changing Fork Oil without Special Tools?
« Reply #20 on: February 03, 2018, 02:52:04 PM »
anyway, how hard can it be?  remove the top screw, take the spring out, pump the oil out. then add the oil, compress the fork and insert any rod or measuring tape to the point where it touches the oil, so the air gap can be measured, and remove or add oil.  am I missing something?  considering that the front seems to be a bit on the soft side, can creating smaller air gap be an option? 

Offline Rtwo

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Re: Changing Fork Oil without Special Tools?
« Reply #21 on: February 03, 2018, 03:25:57 PM »
It takes more pumping and draining than you'd think, it just keeps producing more. When you think it's all out, another pump produces more.

If you overfill, which is easy to do, you could do with some way of sucking out the excess. that's why some sort of fixed pipe the correct length makes it easy.


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Offline Kris

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Re: Changing Fork Oil without Special Tools?
« Reply #22 on: February 04, 2018, 11:19:37 AM »
*Originally Posted by Rtwo [+]
It takes more pumping and draining than you'd think, it just keeps producing more. When you think it's all out, another pump produces more.

If you overfill, which is easy to do, you could do with some way of sucking out the excess. that's why some sort of fixed pipe the correct length makes it easy.

I don't mind pumping:)  I thought of using a syringe with a rubber hose cut to the length of 108mm to correct the oil level; I used one for reverse bleeding.  I was worried that compression tool is required, but apparently, it is not needed for XR models.  the manual says: 'the top cap IS NOT under the spring tension.'  My service manual is for models up to 2013, but I guess not much has changed? 

I am also wondering if one can play with air gap a bit to harden the suspension...  I know that too small gap would reduce the fork travel, but perhaps there is some acceptable room for changing the air gap? I find the front a bit on the soft side.                                                                                                                                                                                                                               

Offline Rtwo

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Re: Changing Fork Oil without Special Tools?
« Reply #23 on: February 04, 2018, 11:23:51 AM »
*Originally Posted by Kris [+]
I don't mind pumping:)  I thought of using a syringe with a rubber hose cut to the length of 108mm to correct the oil level; I used one for reverse bleeding. 

That's how I said do it earlier, I use the the aerosol cap to sit flush and the ball point tube set to the length I want.
It's then just a case of using a syringe to draw out the excess. So simple and you don't need three hands
Tinkering is what happens when you try something you dont quite know how to do, guided by whim, imagination, and curiosity.

Offline Kris

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Re: Changing Fork Oil without Special Tools?
« Reply #24 on: February 04, 2018, 11:39:52 AM »
*Originally Posted by Rtwo [+]
That's how I said do it earlier, I use the the aerosol cap to sit flush and the ball point tube set to the length I want.
It's then just a case of using a syringe to draw out the excess. So simple and you don't need three hands

yes, right. this would be more precise.  for removing the front axle one needs 17mm Allen key?

Offline Rtwo

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Re: Changing Fork Oil without Special Tools?
« Reply #25 on: February 04, 2018, 11:41:29 AM »
*Originally Posted by Kris [+]
yes, right. this would be more precise.  for removing the front axle one needs 17mm Allen key?

yes a 17mm and a 6mm for the pinch bolts
Tinkering is what happens when you try something you dont quite know how to do, guided by whim, imagination, and curiosity.

Offline Kris

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Re: Changing Fork Oil without Special Tools?
« Reply #26 on: February 04, 2018, 12:17:42 PM »
*Originally Posted by Rtwo [+]
yes a 17mm and a 6mm for the pinch bolts

Rtwo, thank you!  I am confident that I am up to the task. It does not look any more complicated than old fashion forks.  If I mess it up, I will let you know :)

I was wondering about another thing.  When I replaced the oil in my Enfield Bullet, I wasn't aware that after pouring the oil one has to pump the shock in order to expel the air, since there one does not need to measure the air gap.  Could the air trapped in the lower portion of the shocker cause some potential problems?

Offline KildareMan

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Re: Changing Fork Oil without Special Tools?
« Reply #27 on: February 04, 2018, 05:28:26 PM »
Yes that's why you should put in about 300ml then exercise the damper rod maybe 10-15 strokes before continuing to pour.
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Offline Kris

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Re: Changing Fork Oil without Special Tools?
« Reply #28 on: February 05, 2018, 01:16:37 AM »
I understand that for measuring the air gap pumping is needed, but if in older forks the air gap is not specified, just the quantity of oil is, would not the air from the bottom make its way up eventually?  I am asking because the is a clunking noise in my fork during decompression after harder braking, so I am suspecting that some air maybe is trapped at the bottom causing metal to metal contact.

Incidentally, in my CRF250 with Ohlins spring, there is a small relieve screw on the top cap that one should open after the first 100km to get rid of the excess air.

Offline AvgBear

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Re: Changing Fork Oil without Special Tools?
« Reply #29 on: February 05, 2018, 05:30:24 AM »
*Originally Posted by Kris [+]
...in older forks the air gap is not specified, just the quantity of oil is
my CRF250 there is a small relieve screw on the top cap that one should open after the first 100km to get rid of the excess air.
There will always be a column of air trapped above the oil in the standard hydraulic front fork tube that must be dealt with as the trapped air, itself, becomes a spring (of sorts).
Off road competition bikes have often used bleed screws to relieve trapped air -- relying, then, on purely spring action and hydraulic damping.
Likewise, there've been air-caps that allowed for pressurized air chambers for additional "spring".
Old poem from 'back in the day':
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They're built like rocks to take hard knocks -- it's the Harleys that give all the grief.

 


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