Rocky shock rebuild using modern parts

[Champ85 609]

If you have a Kyosho Rocky and the original shocks, you already know how difficult they are to restore.

One of the biggest reasons for this is because the shock shaft is an integral part of the piston design.  The piston itself is unlike any other shock design by Kyosho:

Unique shock shaft:

Unique piston (notice that it is very thin and hollowed out with notches on either side):

Tiny little spring to allow the piston to slide on the shaft to alter the shock vs rebound damping rate depending on impact force (non-adjustable unless you replaced the spring itself):

 

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Due to the unique shock shaft design, I decided to forget about using the original piston and spring and switch to a modern piston based on the Kyosho Optima re-release shocks.

Here are the original Rocky shock parts I am going to use not including the original red plastic spring retainers (we'll see them later in the pictures).

The original springs, cylinders and screws:

The original end cap:

The metal end cap washer responsible for keeping the o-ring from popping out of the end cap after installation:

 

 

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The parts used:

Kyosho OT239 Front Shock Shaft (Kyosho Optima re-release).   You will need 2 sets to rebuild the 3 Rocky shocks.

Kyosho OT209 Shock Piston (Kyosho Optima re-release). You will need 2 sets to rebuild the 3 Rocky shocks.

Kyosho W5181-03 Shock Pistons.  Note that we will not be using the pistons in this set, only the small washers (there are 8 of them in each pack, enough for 8 shocks).

Team Durango TD310671 O-Ring 9*1mm (10 PCS).  These will be used to seal the end caps to the cylinders.  Note that Kyosho W5181-04 Shock Seal O-Ring(S) (no picture) can also be used, however this part is getting harder to find and they only come 4 to a pack.

Kyosho ORG03BK O-Ring (P3) (Black/10PCS).  I am sure other o-rings that are the same size can be substituted, but these are what I used.

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Now for the rebuild itself.

Step 1:  Insert a small white washer from the W5181-03 parts tree into the end cap.

Step 2: Insert a 3mm O-ring from ORG03BK.

Step 3: Put the 9mm x 1mm O-ring from TD310671 or W5181-04 on the end cap.

Step 4: Get a shock shaft from OT239 and then select a piston from the OT209 piston tree (there are 3 different pistons to choose from) and also grab one of the spacers.

Step 5:  Assemble the pistons onto the shafts using the supplied e-clips.  Note that the spacer washers are used to limit the shock travel and are outside the e-clips and thus free to slide down the shock shaft.  In this picture they are pushed against the piston but they can slide off easily.

Step 6: Grab your bottle of favorite silicone shock oil.  Insert the shock shaft/piston assembly into the Rocky shock cylinder and fill the cylinder with oil up to the end cap threads.

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Step 7:  Tap the side of the shock cylinder to help get the air bubbles out.  Pull the shock shaft up about halfway and push it back down quickly to dislodge more air bubbles.  Wait for air bubbles to rise to the top surface and disappear.

Step 8:  Install the end cap washer over the shock shaft and into the shock cylinder, making sure it is seated uniformly against the lip inside the shock cylinder.

Step 9:  Put some silicone shock oil on the shock shaft o-ring that is installed in the end cap.  This lubricates the o-ring so the shock shaft threads do not cut it during installation.

Step 10:  Push the shock shaft through the end cap, then screw the end cap to the cylinder.  Test the shock shaft to ensure it is not hydrolocked when fully pushed in to the cylinder.  If the shock shaft won't push in all the way, unscrew the end cap to allow a little but of oil to leak out and relieve the pressure, then screw the end cap back down.   The outer o-ring should seal the end cap to the cylinder preventing oil leakage.

Step 11:  Using shock pliers or many layers of paper towel to prevent damage to the shock shaft, grip the shaft and screw on the original ball end.

Step 12:  Install the original Rocky spring retainer, using the screw to tighten it in place.  Slide the shock spring into place, then the shock spring end retainer.  Done!

I have now rebuilt nine Rocky shocks for three cars using this method and it works really well.  The shocks look original on the outside, but are using readily-available parts on the inside.

You might be thinking why not just use the re-release Optima shocks instead of going through all of this work?  The truth is I have not actually tried it because I do not have a built set of front or rear Optima shocks to try, so I do not know if the compressed or extended length matches the stock Rocky shocks.  I did compare the cylinders and the front shock cylinders on the re-release Optima are shorter than the Rocky shock cylinders and the rear shock cylinders are longer than the Rocky's so they do not have the same look and may not have the same travel length.  Plus they are anodized red and I wanted to use the original Rocky shock parts for the original vintage look.

[Champ85 609]

Mounted on the car: