Author Topic: Gravity defying fork oil  (Read 1057 times)

Offline flashblack

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Gravity defying fork oil
« on: 13.03. 2010 18:45 »
A bit of an odd one this, i`ve had oil leaking out of my fork top nuts, apparently coming up the threads, i`ve loctited the threads now which should cure it, but i was wondering if anyone has an explanation for it? Seems illogical to me, cheers, confused but happy, Rich.
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Offline BSA_54A10

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Re: Gravity defying fork oil
« Reply #1 on: 14.03. 2010 02:55 »
The usual culprit is too much fluid in the fork legs and the prime reason for this is generally water ingression, the other biggie is an over zealous owner with an oil can.
Drain out the oil and see what is in there.
Bike Beesa
Trevor

Offline bl**dydrivers

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Re: Gravity defying fork oil
« Reply #2 on: 14.03. 2010 04:19 »
i believe it is too much oil but on the threads instead of using threadlock why dont you use ptfe tape thats the best stuff right there.

Offline flashblack

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Re: Gravity defying fork oil
« Reply #3 on: 14.03. 2010 07:44 »
Trevor, regarding the quantity of oil, it has the recommended 213cc of 20 weight, and last weekend i was sat on the drive letting the engine warm up, watching oily bubbles emerge from under the heads of the fork top nuts? Seemed to me to be pressure related, and reminds me of a problem i recently had on japanese bike on which i had removed the fork legs to renew the head bearings, on testing the action of the forks, one was very stiff and practically unmoveable, so ,halfway through undoing the top nut, there was a loud hissing release of a huge amount of pressure, which resulted in the fork working properly again? Can`t figure out how so much pressure had built up (other leg was fine), regards the A10 fork, i can only imagine temp change has something to do with it?
BD, agree with you regards the ptfe tape, but at the time i had no tape, so being too lazy to go buy some at that time, loctite it was!

cheers Rich.   
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Online bsa-bill

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Re: Gravity defying fork oil
« Reply #4 on: 14.03. 2010 09:05 »
I have had this and upon draining the fork oil found it to be contaminated, so my thought would be same as Rich -  water.

All the best - Bill
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline MikeN

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Re: Gravity defying fork oil
« Reply #5 on: 14.03. 2010 10:45 »
,halfway through undoing the top nut, there was a loud hissing release of a huge amount of pressure, which resulted in the fork working properly again? Can`t figure out how so much pressure had built up (other leg was fine), regards the A10 fork, i can only imagine temp change has something to do with it?


cheers Rich.   

Think about it.The oil seals are designed to keep oil in against pressure but not nessesarily to stop the ingress of pressure.So when the forks are working there must be a tendency for there to be a derpession as they extend drawing air in and a pressure build up as they compress.Its like a big bicycle pump that doesnt let air out until you take your finger off the end (or unscrew the top nut in your case).You must have really excelent fork seals!
Mike

Offline flashblack

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Re: Gravity defying fork oil
« Reply #6 on: 14.03. 2010 14:26 »
Bill, i`m pretty sure it`s not water ingression, as i recently changed the oil, and found no contamination in the old oil either ( even the old stuff was only six months old).

Mike, i was also surprised the seal held that amount of pressure in, and also, that i didn`t feel any difference when riding it!

Cheers,  Rich.
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Online bsa-bill

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Re: Gravity defying fork oil
« Reply #7 on: 14.03. 2010 14:37 »
So now we know we have hydraulic come Pneumatic forks  *smiley4* *smiley4* *smiley4*

I agree with Mike though as certain seals used on farm machinery are in what would seem to be the wrong way around so that overgreasing is not an issue as the grease can escape past the seal but soil and water wont get in from the outside world.

All the best - Best
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco