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Fork oil question

2K views 23 replies 13 participants last post by  plodalong 
#1 ·
I don't have the service manual just wondering if I should have the fork oil done next time I bring my bike into the mechanic. I have a 2007 Bonneville T100 with 30,000 miles. Is this normally included in the tune-up or should I expect the mechanic to charge me extra for it and how much time to they usually spend on this?

thanks!
 
#2 ·
Well, at 30,000 miles it'll need a change if it's never been done. See what's on the 30K checklist and discuss with your dealer. The job is a real PITA and time-consuming since the forks have no drains... :(
 
#4 ·
I changed mine with a $9 hand operated vacume transfer pump from harbor freight . When I changed to progressive springs I played with different weights and this came in very handy .
 
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#15 · (Edited)
The hidden gunk



As stated by LR in a previous post, the job done this way is half done. The wear particles that have been shed from the sliding parts are still sitting in the bottom of the forks, around, inside, and underneath the damper rod.
To do a thorough job the forks need to be flushed several times with a solvent and some pumping action on each flush, ending up with a fork oil flush, and then hung inverted overnight to drain. You will be amazed at all the gunk that comes out.

After that initial flush a hand pump would be useful for experimenting with different weight oils.

Why is this such a PIA? Appears to be straight forward, remove wheel, 22mm wrench to open the top of the forks and 4 -8mm pinch bolts and the legs fall right out no?
Again as LR stated it can be a PIA. Of course it's easy enough to disassemble, it's the return trip that can be frustrating, when getting the fork leg/s to slide thru the headlight ear.

What I do on these bikes is to pull one leg at a time, leaving the other to hold the headlight assembly in place. That way the open headlight ear and rubber bushing is much easier to realign when inserting the leg. Also a good spray of silicone to the bushings helps with this.

Charles
 
#9 ·
Maybe OK if the oil isn't much degraded but less wise for a viscosity change. FWIW, quite a bit stays in the bottom and needs to be pumped inverted to get it out and then left to drain before pumping again.
 
#12 ·
Did a fork oil change last week. One thing to watch when using synthetic oil is that the headlight mount tube rubbers swell when they get coated in the oil and there's no way they will fit then.

Luckily I had a spare set from a load of spares I bought a few years ago.

Yes there was mucho swearing, didn't help that it was 110f at the time. Still the beer tasted real good once I had finished.
 
#17 · (Edited)
One at a time worked good for me. Flushed them out good and let sit for a bit too drain the yucky stuff out. AMAZING difference on the ride after that. It's incredible what we slowly learn to put up with since time erases memories of how well new fluid was...

Make sure to get the correct level on both tubes. I was told the air gap overrides the fluid amount. I had to siphon out a little to get the gap right. Next time should be much faster.
 
#18 ·
Ironically I changed my fork oil this morning and would like to share a little boneheaded "what not to do" for Scrambler owners.

Bought a liter of some fancy fork oil. Pulled one leg, drained, decided to splash a *very* small amount of the new oil in it to help drain out any sludge. Filled to stock 123mm air space for the Scrambler.

Pulled the other leg, did same flush thing. Fill up leg with remaining oil and fills to about 15mm too low. MF.

Option A is to buy another liter of oil for a tiny amount or B split the difference between the two and go with a slightly larger air gap. Thinking B but walking away for now to go on a mountain bike ride.

TLDR: flush with something else if you buy a liter for a scrambler.
 
#20 ·
I remove the entire fork assembly with the wheel still attached. I remove the caliper, loosen the pinch bolts, and pull the whole front end off. Then the wheel is still aligned and all is nice and easy. Plus I can roll the forks over to the picnic table to dump them out in a bucket.
 
#21 ·
Right..., but we all know that you're Superman. :D
 
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#23 · (Edited)
I plan to change mine this week. I'm going to have the front end apart anyway to do the steering head bearings. What's the best solvent to use to flush 'em out? I don't want to damage the existing non leaky seals.
 
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