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Old 05-07-2008, 11:36 PM   #2
meat popsicle OP
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Joined: Feb 2004
Location: Circumlocution Office of Little Dorrit
Oddometer: 14,260

Is your bike dirty? Are your forks caked with mud? You should always clean your bike up first so crap doesn’t get inside. Might as well not service it if you are just going to get dirt and crap in the fresh oil during the job… so get scrubbin’!

Get the forks off the bike

Use LC4 Laramie’s Steering head bearing, a how-to-guide… to get your forks dismounted BUT use the following changes:

1) Loosen the upper triple clamp pinch bolts, then loosen the fork caps from the outer tube, before loosening the lower triple clamp pinch bolts. This will allow you to use the lower triple clamp as a vice to hold the fork legs while you loosen - but not disconnect – the fork caps.

2) You may need to use something to pry open the triple clamps in order to slide the fork legs out. With my triple clamp pinch bolts completely removed I couldn’t budge the fork legs without wedging the clamps open a bit.

3) I removed the handlebars so I could use a socket on the fork caps. If you are dismounting your forks for service, you probably should be checking your steering head bearings, so you might as well since its part of Laramie's how-to.

Well, there they are… I wished mine were still mounted too, but ya might as well continue.

Open them up, remove the springs, and drain the oil

Open one fork leg and let the outer fork tube slide down; don’t worry fork oil won’t spill as long as its upright. Then fit your special narrow-width spanner onto the hydraulic stop, as pictured below, by pulling the spring down and holding the fork cap up.

You can now get the fork cap off the cartridge assembly. The wrench is now holding the spring down, so pull down on the spring a bit to remove the spanner and then the spring can be removed. You should notice a thin hollow rod sticking out of the inner assembly. If not, and it is sitting flush or inside the piston rod, then pay attention to the rebound needle business below. Either way pull it out; pre-2003 48mm USD forks should have a o-ring on that rod.

Now you can turn the rest of the fork upside down, gently, and pour out the oil. I said gently because if your rebound needles are not stuck and you are rough with the fork while it’s upside down they may fall out with their springs. So take it easy at this point when turning the fork leg upside down. Pumping the piston rod will help release the oil in the cartridge, and I found that leaving them upside down in my drain pan overnight helped too. I wonder if pumping the piston also helps stir up any grit that has settled out so you can pour it out with the old oil… that would be good.

Once you have drained the oil you can either continue with the disassembly or begin reassembling. You should more fully disassemble your forks if:

1) your fork oil looked bad enough to warrant some cleaning,
2) your rebound needles are frozen,
3) or you were going to replace the fork seals and/or revalve the stacks.

If the fork oil looked good, the rebound needle was springing, and no revalve and/or fork seal replacement was going to happen then you could simply pour in new fork oil, set your oil height, put in your old springs (or your new ones), and close ‘em up. (Remember new springs will require you to set the preload, which is not covered in this guide - see your fork manual.) If not, it probably would be a good idea to disassemble them and do some cleaning. If you are good to go, scan below for where to pick up with the assembly.

Now what about this rebound needle business?

Based on what the suspension tuners both said, the rebound needle is the most vulnerable part of these forks. There is no fork oil inside the inner assembly, unless you poured it in the wrong place… then you might notice oil weeping out of your rebound clicker Anyways, the rebound assembly is not bathed in oil so the bore (made out of plain steel) can and will rust as moisture makes its way inside your forks. This will render it non-adjusting and eventually might interfere with the fork’s rebound. If for no other reason, this is why you must service your forks annually!

You can check to see if yours have rusted by pressing on the rebound adjustment rod before removing it from the inner assembly. The rod should extend a bit (less than ”) out of the inner assembly when properly seated on the rebound needle down yonder, and if you push on it you should feel the rebound needle’s spring. There's my lil' rod sticking out in the picture above! If not then the needle is likely frozen in the bore and will need further attention.

NOTE: the following rebound needle information in this paragraph is out of the disassembly order; I put it here to help you understand how much further you would need to disassemble in order to service the rebound needle. A trick I was told is to use a small Allen wrench to try and push the rebound needle from the bottom of the rebound assembly. Again, you can’t see it until you disassemble the cartridge, but there is a small hole on the bottom of the piston that goes straight through to the rebound needle. You can see the hole in the bottom of the rebound piston pictured below. The needle is made of soft metal so don’t push too hard! Just give it a moderate push and see if this frees up the needle so that the rebound adjustment rod sits above the piston rod and you feel the spring’s action.

If not then you will need to disassemble the rebound assembly from the piston rod, which requires a soft-jawed vice or some other way to hold the piston rod without damaging its finish while you remove the rebound assembly “complete”. The shop manual says to secure the piston rod by grabbing it along the length that will be covered up by the hydraulic stop, probably to minimize any risk to its finish. Removing the rebound assembly from the piston rod will expose the rebound needle and bore where you might be able to clean them up, depending on how neglected they were...

I watched my fork tuner open up the assembly, then make a drift out of a stout piece of soft wire (aluminum) that he rounded on a grinder, and then punch out the rebound needle through the same hole in the bottom of the rebound assembly used for the trick noted above. The needle is brass (soft) so if you have to hit it too hard you probably will damage it. He then cleaned everything up to restore the bore and needle, but again if you can’t restore the bore and needle you will have to replace them. Finally, he found one of the springs was rusted away to oblivion and the other was permanently squished from being stuck in one position. He salvaged one spring from another person’s assembly that was completely replaced and said they would probably do OK, but recommended replacing them. BOTTOM LINE: if you keep up with servicing your forks you can limit the amount of water that remains inside the fork, which will help you steer clear of this mess.

Remove cartridge and base valve from the fork tubes and disassemble it

OK (breathe), I’ll continue with the teardown and those not needing more can scan below in Post #3 for where to jump back onboard. Now you need to remove the inner assembly from the fork tubes. To do this, pry off the rubber plug covering the compression adjustment clicker on the bottom of the fork leg. You can then use a socket to remove the compression assembly (aka base valve) from the cartridge. Once you separate them you will be able to remove the cartridge and then tap the compression assembly out of the fork tubes. There is one useful tip in the shop manual on this: extend the piston rod and hold it to one side – gently bend it to one side and hold it there – which will keep the cartridge from spinning while you unscrew the base valve.

In order to reach your rebound adjustment needles and rebound valve stacks you will need to disassemble your cartridges further. But do not follow the steps in the service manual! It will guide you to remove the screw sleeve from the tube, which is a royal pain due to the number of threads and/or amount of Loctite on them. Both tuners recommended a workaround: remove the hydraulic stop/spring guide, which will allow you to drop the piston and rebound assembly out the bottom, leaving the screw sleeve and tube of the cartridge assembled. Be ready for the piston ring to fall off. And be nice to it; that is what creates the seal within the cartridge to direct oil through the rebound and compression assemblies.

That does it for the amount of disassembly I performed. This exposes the valve stacks for both rebound and compression. If you are game, here are two local threads that may help you revalve your own forks: Zerodog’s fork mods and one more with valve info. If not, but you would like to improve your forks get a tuner that knows LC4s. I know of one in San Francisco and another in Salt Lake City and both seem to know their stuff and will take care of you. As one tuner told me, the LC4a’s forks are setup very oddly by the factory; as I recall he said something to the effect of: soft springs with harsh valves is a bad combination.

If you are replacing your fork seals I can’t help you with any tips on further disassembly/reassembly for that; perhaps someone here can fill in this bit of information. Here is one thread on cleaning your fork seals without disassembling: cleaning fork seals

EDIT: Zerodog has graciously added a summary of his experiences with various fork seal brands that are available for (some) LC4 forks HERE or on page 3.

meat popsicle screwed with this post 05-12-2010 at 01:27 PM
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