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Offline pennpeel

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Fork Oil renewal problems
« on: March 07, 2021, 10:37:26 AM »
Someone asked to let them know how I got on with my fork renewal problems.

Well, ok is the answer, but i still have a problem I think.

Forks came out no problem when when I found out to loosen the top pinch bolts, drained the oil, topped it up no problem to 107mm as per the Haynes manual, quite tricky to get it dead on but i'm sure its ok.

Problem came as I put the spring in and a bit of oil overflowed the outer tube, as I hadn't pulled it up properly. Not alot so I put the fork back together and did the other one no problem put them back on the bike with a view to torqueing everything in the morning I then found myself thinking over night did the oil that overflowed make a difference?

On the video  (Tinderbox art)

I watched to do the job, as well as reading the Haynes manual the guy said for ref. he'd measure the oil level with the spring in for ref.  Brilliant I'll undo the fork again check the oil level 40mm with the spring in and all is well.

That's where it goes wrong, My level is about 60mm 20mm difference. I did pump the fork repeatedly as per video and book probably more than required but better more than less.

So next thing was get the spring out, measure from scratch a i'll be sure, but i can't get the spring out, with out tipping the fork and the new oil coming out to.

Not a big problem i'll just require another bottle of oil.

So any thoughts on why its so different? I'm sure my 107mm is right I checked it a number of times then, held the rule and got my wife to check it again. Obviously now I've draw out the inner tube which was covered in oil and spilled a bit, (although i did drain as much as I could into the fork as I withdraw it.

In the Haynes manual it shows in the picture 7.1 the piston extended but in the video and the Haynes manual it says fully compress the rod.

I bought a litre bottle but in the manual  in the spec in the Haynes manual 619cc, have I mistaken the quantities? The guy in the video had a 430 ml bottle presume for each fork. I'm a bit confused now.

The options are drain that fork again get the spring out, and start again or ignore what the guy said about the 40mm. The bike is a 2012 800 xc Any Ideas please.

Offline crispey

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Offline mcinlb

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Re: Fork Oil renewal problems
« Reply #2 on: March 07, 2021, 04:53:05 PM »
Initially , when draining the oil, you've got to make sure all the old oil is pumped out of the damper unit.
Similarly, when refilling, you've got to ensure the damper is bled through with fresh oil so the amount you put in is close to the recommended.
I tend to measure the amount , from the fork top to check amount , but only when I'm sure the damper unit is full also..

Offline AvgBear

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Re: Fork Oil renewal problems
« Reply #3 on: March 07, 2021, 11:13:16 PM »
I should've mentioned this earlier: when changing fork oil, I measure the fork oil I get out of each fork as it's difficult - without full disassembly - to remove 'all' the oil. It's just more info...
If the bike is from new, one can assume it's got the proper amount. What you get out when draining may be different -- but may be the amount you'll want to replace. Again, more info...
There are a terrible lot of lies going about the world, and the worst of it is that half of them are true.

Offline pennpeel

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Re: Fork Oil renewal problems
« Reply #4 on: March 08, 2021, 05:24:08 PM »
As ever thanks for the advise, with a little time to think about it.  I'm going to try and hook the spring out with a bit of wire wrapped in tape, measure the levels again, pump it again repeatedly check and double check my measurements. I've just ordered a new cap bolt from Fowlers as I mangle the old one getting it off. I'll probably get some more oil just in case I need it. Its a pain, but I want it right. Its still alot cheaper than getting a garage to do it. A bit of a learning curve as well.

I don't use the bike as regular transport so I can take my time and do a bit at a time.

Once again thanks all :)


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