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Discussion Starter #1
I'm on a bit of a mission, forever fiddling with the forks looking for the perfect front end ...Aahem! Draining the oil requires the removal and inverting of the fork tubes which is time consuming. I intend to try many ideas and I ask the collectives knowledge bank: can I drill and tap the lower leg to drain oil more easily? I'm sure this feature was on my ST1100 some years ago. Has somebody a cross section view of the fork leg? If it can be done and I think it can,what would be the lowest practical point I could fit a bleed screw?

In anticipation, Many thanks.
SATURN 5
 

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I'm on a bit of a mission, forever fiddling with the forks looking for the perfect front end ...Aahem! Draining the oil requires the removal and inverting of the fork tubes which is time consuming. I intend to try many ideas and I ask the collectives knowledge bank: can I drill and tap the lower leg to drain oil more easily? I'm sure this feature was on my ST1100 some years ago. Has somebody a cross section view of the fork leg? If it can be done and I think it can,what would be the lowest practical point I could fit a bleed screw?

In anticipation, Many thanks.
SATURN 5
Someone else suggested doing that. Either VSRI or here.

Almost certainly voids your warantee (etc), but yes, it's been done on other bikes, the trick is knowing where to drill :). When you find out, let us all know.

Shouldn't need a large hole, 3mm is probably enough if you are prepared to pump the forks up & down.

Pete
 

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Someone who rebuilds the suspension components as a business may be able to assist you.

I'm expecting to go through my suspension (front and rear) this coming winter to rebuild and upgrade it. One of the mods that I want to have done (by who ever does my work) is exactly what you are talking about.
 

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.....Someone else suggested doing that. Either VSRI or here.....

..... the trick is knowing where to drill :). .....

Pete
...and we never hear back from those who suggested it...

From memory on my last complete dis-assembly, that oil lock piece pretty much fill up the last 25 mm of the fork stanchion- so the hole would theoratically has to go higher up from that... but please dont take my word - do a complete disassembly to measure yourself. U should put new oil seal upon reassembly.

Saturn 5, i feel your pain- i have changed fork oil about 20 times in the last 2 years in my search for the perfect setup. I can do the whole thing in about 2.5 hour now- and at least 1/2 hour is spent ensuring the forks are assembled correctly so the fork actions are as smooth as possible - this particular process really helps the fork in dealing with small movements and make them feel more compliant.
 

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Discussion Starter #5
Bleed Screw

When I find the correct info. on this I will post the details. It may encourage others to change the oil more often. Fork oil becomes completely grey in colour after the first 10,000kms (6000miles) The process of changing the oil is not difficult but it is time consuming.
 

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If you're someone who is changing viscosity constantly then tapping a hole may be a small benefit. For people just doing it as part of normal maintenance though I don't see it.

Even if you have the drain holes you still really need to pull the front wheel and fender so that you can cycle the forks up and down to get all the old oil out, and to compress each leg to set the oil level correctly. You also have to loosen the top triple clamp bolt and remove the fork cap. So the only additional work to pull the leg is loosening the lower triple bolts and the caliper hose routing bolts. 5 minutes tops, both directions.
If you sync up fork oil changes to front tire swaps you're only looking at 1/2 hour extra to do the fork oil too.
Even starting from scratch it's no more than 1 hour, and that's not working fast. (I'm a pretty slow mechanic. :) )
 

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...,what would be the lowest practical point I could fit a bleed screw?

Of course it CAN be done...considering the pitfalls it's rather : should it be done?

The tubing has a wall-thickness of 1.5-2mm, the "bottom plug" which houses the bolt which fixates the damper rod is too awkward and too narrow to drill and tap a second hole parallel to the damper rod bolt...as it's also recessed from the axle-bore and impossible to get tooling onto/ into.

Which leaves you with the side-walls of VERY thin alum-cast. Even with a superfine-thread, things would be very questionable....there's also no machined surface for the drainbolt to sit against.... and perfectly flush at that for any seal to work properly.

Which leaves some "butter"-welding to create some "meat" to machine/drill/tap etc a boss solid enough to house the drain-screw.
Meaning... taking some serious heat to the machined tubing of the boot, arghhh


And those fork-boots are well over A$500 each (local price)....just giving things a try could well be a fairly expensive exercise.
 

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+1 on what Glitch said on the topic. Once u find the correct setting, it's a once every 10,000km exercise anyway.

The fork lowers can be had from the States for about $700 landed for the pair if u are really inclined.

the other thing is that to get rid of the crap in the forks - u really need to unbolt the bottom bolt, cycle the forks and pump things out and leave the forks standing for at least 15 minutes to drain things out. - i usually fill with a thinner oil such kero to clean things out, before filling up with fresh oil - of course u dont need to be as anal as me:green_lol:
 

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Discussion Starter #10
The fork leg wall thickness looks a tad thin for a bleed screw. Looks as though I'll continue to pull the fork legs as before. It was just a thought. Thanks Pete and others for the H.U.
 

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FWIW: Plan-B - the method I use.

Just pull the springs out and suck as much oil as you can out the top.

That still leaves some old oil at the bottom, so do the first couple of oil changes close together - which you probably will if you are fiddling with getting the viscosity right.

After the second change the oil is pretty clean and being so easy there's no disincentive to refreshing the oil more often - which also means the bit left matters less after those first couple of "changes".

Pete
 
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