LC4 shock rebuild parts?

[rz35027]

Has everybody seen this?


http://www.advrider.com/forums/showthread.php?t=301977

[Tseta]

(Bump for the shock service questions on the previous page...)

Here's another good link regarding the LC4 rear shock. This discusses shock shimming. Probably a bit more advanced than just simple servicing, but very interesting nonetheless.

Click here.

-T

[Luke]

Originally Posted by Tseta

Thanks Luke for the explanations and the alternative part sources. I had a look on the McMaster site for the part numbers and did some research, to make it easier to obtain these parts, especially for those of us not in the US.

It seems that the shock shaft bushing is in fact just a "quite" standard 14mm plain bushing. This type of bushing could be obtained from, for example, INA ( click here). The bushing measures 14mm i.d., 16mm o.d. and 12mm in width. These bushings may be available with either steel or bronze backings, but as Luke said, the steel version should probably be used.

The shaft seal looks to be a quad-ring (an "o-ring" with an cross-section in the shape of an x). Converting the inch sizes to mm sizes results (at least close enough) in a 13,95mm X 2,62mm "standard size" quad ring. Buna-N material is equivalent with regular NBR.

-------

I have some further questions as well. The WP shock manual is slightly vague at best. I hope someone can shed some light onto these issues.

Is it necessary to calibrate the new bushing with the calibrating mandrel when replacing it? Interestingly, KTM supplies these shaft seal parts as "one piece", but the service, according to the manual, still requires fidgeting with the individual components.

How about the reservoir piston, then? Is it necessary to unscrew the reservoir body from the shock casting (using the special tool) to gain access to the reservoir piston? Why couldn't one just unscrew the reservoir cap and take the piston out from that side? This way, one could leave the reservoir body in place and so many special tools wouldn't be needed to service the shock.

Cheers,

Tseta

Those are the right parts. The O-ring I mentioned is a standard size. It's an AS568A-113 AS568A is the series, 113 is the size.

You don't necessarily need the special tools to unscrew the reservoir caps but you need some way to hold the body because they are on tight. After you get the cap unscrewed the first time you probably won't need the tool again, unless you loctite it like they do from the factory. I made a clamp on a mill, but if you don't have a mill you could probably rough one out with a saw and then mould some JB weld to get the size just right.


I made a pin wrench because the one I bought wasn't strong enough. I haven't tried this, but the best DIY design I've heard of is a big Crescent wrench (adjustable open-end wrench) with a couple of holes drilled in it and hardened steel pins pressed in to the holes.

Originally Posted by dentvet

who sells a good adjustable pin wrench?

i have a nitrogen cylinder and regulator, what else do i need for recharging operations?

i have a vacuum pump collecting dust, what's it good for?

For recharging, you either need the special WP charging attachement or convert the shock to a schraeder valve. You can use the vacuum pump to help bleed the shock. It's not necessary, but it's easier to get a good bleed if you have one.

[rz35027]

"I made a pin wrench because the one I bought wasn't strong enough. I haven't tried this, but the best DIY design I've heard of is a big Crescent wrench (adjustable open-end wrench) with a couple of holes drilled in it and hardened steel pins pressed in to the holes. "

That's what I built. 12 in Crescent wrench (10 in wasn't big enough for resevoir body) drilled with 11/64 holes, drill shanks cut off and epoxied in... Buy some cobalt drill bits... the wrench body is hard stuff, you may toast a few bits doing this.

The shock body has the 11/64 holes, the resevoir body holes are larger and farther apart.

I used a 30 in x 6 in x 3/4 in piece of nylon (plastic) (it could be plywood) with holes (cut with a holesaw) (about 1/2 in apart) for the shock body and resevoir, to use as a means of holding the shock while opening both parts instead of just reefing on the head of the shock in a vice.

Those things are on tight! It took quite a bit of heat (hot to touch) and two of us to get the shock body apart.

Good question on the bushing mandrel...

Now for some kind of bleed system...
Is it possible to do this without a vacuum pump? Just take more time and patience to get it?

[Tseta]

I got some 14mm plain bearing bushings. I had an old "adapter cpl" that had been changed by the shop at a previous shock service. I was able to easily disassemble the "adapter cpl" and press out the old bushing, as well as pressing the new bushing in, using just regular sockets and a vice. The calibrating mandrel is and the necessity of it's use is still a big question mark in my book. It is not too expensive, though:

Part Number: T149
Description: CALIB. MAIN BUSHING D=14
Retail: $30.77

I've been trying to source some quality pin wrenches to take the shock body and the reservoir caps off. This part is clear and obvious, the caps must come off for the shock service. The unclear part is whether or not the actual reservoir body needs to be unscrewed from the shock casting during servicing. The WP manual is really vague on this part. Is it possible (feasible, recommended) to take out the separation piston if the reservoir body is not unscrewed?

Cheers,

Tseta

[Luke]

Originally Posted by Tseta

I got some 14mm plain bearing bushings. I had an old "adapter cpl" that had been changed by the shop at a previous shock service. I was able to easily disassemble the "adapter cpl" and press out the old bushing, as well as pressing the new bushing in, using just regular sockets and a vice. The calibrating mandrel is and the necessity of it's use is still a big question mark in my book. It is not too expensive, though:

Part Number: T149
Description: CALIB. MAIN BUSHING D=14
Retail: $30.77

I've been trying to source some quality pin wrenches to take the shock body and the reservoir caps off. This part is clear and obvious, the caps must come off for the shock service. The unclear part is whether or not the actual reservoir body needs to be unscrewed from the shock casting during servicing. The WP manual is really vague on this part. Is it possible (feasible, recommended) to take out the separation piston if the reservoir body is not unscrewed?

Cheers,

Tseta

I forgot about the mandrel.... I never used one, I didn't know it was needed. Just press the bushing in from the top with a flat washer and it will end up in the correct place. You need to be careful choosing the socket to hold the bottom of the 'adapter cpl' body as the bushing sticks a mm or so out from it.

The reservior body doesn't need to be unscrewed- the piston can be forced out with compressed air. However, when I first tried to unscrew the cap I held the shock body instead of the reservoir body and the whole reservoir unscrewed so I had to make the tool to get the cap off.

If you do this, be very careful not to damage yourself or the piston. I have modified my reservoir pistons so that they can be grabbed from the bottom. This is really helpful in dissasembling the shock and setting the piston height when putting it back together.

http://www.advrider.com/forums/showp...6&postcount=27 Shock disassembly.
http://www.advrider.com/forums/showp...4&postcount=29
Reservoir piston mod.



Here's how I vacuum bleed the shock. http://www.advrider.com/forums/showp...8&postcount=34 Set up the pump like that, suck the air out and when the bubbles stop then release the vacuum so that fluid gets sucked back in to the shock. Repeat until no bubble come out. Using thicker hose from the shock to the fluid jar makes things much faster.

[rz35027]

A picture is worth a thousand words...

My homemade pin wrench (dirty), ugly but functional...

[rz35027]

The bracket I used to brace the shock while torquing on it...

I intend to use air to blow out the resevior piston, by screwing the shock body cap back on, putting a rubber plug (drilled through) in the hole and applying air. Carefully... And will be installing the "set screw" in the resevior piston.

The stack of shims in my 95 RXC shock has far fewer shims than those discussed in this thread http://www.advrider.com/forums/showthread.php?t=620602

It will be interesting to compare what is inside the other shocks I'm dealing with...

[Tseta]

This has turned out to be a very great thread indeed. Many thanks to Luke for the answers.

The shock service procedure is quite clear to me now, maybe a bit fuzzy around the edges. I'm sure it will all make sense once actually doing the service, hands on.

One additional point that could be clarified more and expanded upon is the piston height setting. Luke's separation piston mod is a good one, and I understand it will be immensely helpful in setting the correct piston height. However, I find the actual height specification and it's measurement confusing. Is the piston height measured relative to the end cap or to the shock body? In other words, if you want to set the piston at 10mm, do you push it down 10mm from the endcap level, or pull it up 10mm from the shock body casting?

-T

[rz35027]

10mm from the shock body. Part of the reason for the gas chamber is to provide room for the fluild displaced by the shock shaft as is goes into the shock body.... Not enough room = hydraulic lock.

How much vacuum does one of these pumps put on the fluid?

I've read a plastic pop bottle can be fitted with tubing, a slight vacuum can be created by squeazing the bottle at the appropriate moment....

[Tseta]

I found a really nice adjustable pin wrench, with interchangeable pins, the Facom 117-B. Some info here.

For the vacuum bleeding, I bought a similar Mityvac-copy that was shown by Luke in a previous post.

Soon I'll have all the tools and supplies necessary for doing the shock service myself. How exciting!

-T

[Desert Silver]

Originally Posted by rz35027

10mm from the shock body. Part of the reason for the gas chamber is to provide room for the fluild displaced by the shock shaft as is goes into the shock body.... Not enough room = hydraulic lock.

How much vacuum does one of these pumps put on the fluid?

I've read a plastic pop bottle can be fitted with tubing, a slight vacuum can be created by squeazing the bottle at the appropriate moment....

I know this is a very old thread but I'm new to shock rebuilding. I've rebuilt everything else but never tried the shock. The question I have is if you set the resivorior piston higher than 10mm would it give you a more progressive compression dampening like raising the oil level in a set of forks due to a smaller volume to compress? By the way the shock is off of a 1996 ATK 406.

[Luke]

Originally Posted by Desert Silver

I know this is a very old thread but I'm new to shock rebuilding. I've rebuilt everything else but never tried the shock. The question I have is if you set the resivorior piston higher than 10mm would it give you a more progressive compression dampening like raising the oil level in a set of forks due to a smaller volume to compress? By the way the shock is off of a 1996 ATK 406.

Not really. For perspective, it takes about 1500 pounds to compress the shock spring all the way. (6kg/mm, 115mm travel) The shaft has an area of about 1/2 in^2, so for 20% extra force it would take 600 psi of pressure in the shock. That would be a bit rough on the seals.