I posted this on Tanshanomi's site, but figured it's time to post it here....
Those cheap eBay RFY shocks are very tempting for a vintage build for around $100 a set. But, right out of the box, they are absolute garbage. They are sure to be under filled with oil and Nitrogen. Generally, they will be about 100cc low on oil and the N2 charge is very inconsistent. I have found that the N2 pressure can be anywhere between 15 psi to 40 psi. They should be around 75 psi.
In spite of all the disparaging comments about these shocks, they can be made to work reasonably well, though. Once modified and rebuilt correctly, they have plenty of rebound damping but the compression damping is a bit light. I have, yet, to figure a way to increase that, but the spring rate compensates pretty good for compression so it is not much of an issue.
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Watch this tutorial, as it very closely resembles the process needed to rebuild the RFY shocks.
Now, watch it again!
EDIT: That video has been removed. I made my own video and a link is posted later in the thread, in post #13.
OK, now you are ready to proceed.
The tools needed to perform the rebuild are pretty cheap and can be made with a bit of ingenuity. You will need a vise with Aluminum soft jaws, a spanner wrench....I bought an adjustable spanner, but the one for an angle grinder works. You will also need to fab up a spring compressor if you don't have one. and you will need a piece of steel tubing (I think you need 1.5" diameter, I don't recall exactly though) . I had pieces of an old porch swing in my scrap pile that I cut up.
First, to fab up a spring compressor, you'll need a piece of flat stock with a slot in it and a hole drilled. I had a couple of piston holders in my tool box that already had a slot, (that had to be widened, slightly), and I had to drill the hole.
![]()
Next, a vise, a 1/2" bolt, some long eye bolts, nuts and washers, and here is my spring compressor:
![]()
Once you have the spring off, it is very apparent that the shock is not completely full. Cycle the shaft a few times, and you can feel and hear the air in the system.
Remove the valve stem core from the valve stem in the N2 reservoir and use a socket and and a dead blow hammer to push the reservoir down enough to remove the spring clip retainer that keeps the reservoir cap in the reservoir. Use compressed air applied to the valve stem to force the cap and bladder out of the reservoir. DO NOT try to pull it out by the valve stem. Once the res cap is removed, you can dump the oil out of the reservoir, at this point.
Next, set the shock up in in the vise and remove the shock seal retaining cap with the spanner. Use A section of pipe between the the pre-load adjustment ring and the spring retainer, with a washer (or two) and the jam nut for the lower clevis, and use an impact wrench to pull the shock shaft out of the shock body. Below is a picture of my home made puller. The pipe I used is a section from an old porch swing I had in a scrap pile.
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Here's everything disassembled:
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- - - Updated - - -
Now for assembly:
One of the reasons that these shocks are not completely full is that the seal is 15 mm high, and there is no way to install it without trapping air in the body. The original seal is at the top.
![]()
Another reason, I am sure, is the QA control at the factory. We are addressing the QA issue by doing the rebuild, but the seal issue has to be addressed, as well. There is a boss at the top of the shock, that looks like it should have an damping adjuster. I paid a local machinist a few bucks to spot face the boss to house an o-ring, and drill and tap a hole for a bleed screw. I used a button head 10-24 Allen screw and an o-ring for the bleed screw. Install the screw and o-ring.
![]()
![]()
Following the video in the previous post for assembly, Fill the shock body with fork oil (I used 10 wt, but you may need to play with oil weight). Insert the reservoir cap with the bladder. Tap it in past the spring clip ring and install the spring clip and install the valve stem core. Next, bump a bit of air in the reservoir and the cap should seat against the spring clip.
If you are going to replace the seal, good luck! I have not found a vendor that sells the 12.5 mm x 32 mm x 15 mm seal. I did find a SKF 12 x 32 x 7 mm seal, and decided to stack two of them in each shock.
![]()
Note: It is advisable to cut a flat piece of thin plastic and wrap it around the threaded portion of the shock shaft to avoid damaging the seal.
Install the shock shaft, being careful not to displace the white teflon bushing. It is prone to moving out of its groove. Using the plastic guide method when installing the shaft is a good idea, here, as well.
Give the end of the shock shaft a few good whacks (to drive air out of the shim stack), and let the air bubble to the surface. Do that a couple of times, and let it sit for a few minutes. Top off the oil.
Place the seal (or seals ) flush with the rim of the shock body and release the air from the reservoir, while pushing the seal into the body. It should draw the seal in. You might need to tap the seal in a little farther. All you need is for it to be in far enough that you can catch a thread with the shock body retainer cap. Use your spanner wrench to tighten up the retainer cap.
Flip the shock right side up and cycle the shock shaft to get any air to the top of the shock. Once there is no air in the shim stack, use the bleed screw to get the rest of the air out and use a syringe or something to top off the shock. Replace the bleed screw and o-ring.
Now, you need to get it filled with 75 psi of N2. In a pinch, a tire shop that has Nitrogen can do it, but their equipment is made to fill tires....and quickly. It is much more advisable to find a shop that does suspension work. (A motorcycle suspension shop, an off road truck specialty shop, a local speed shop maybe) Their equipment will include a feed valve that fills slowly and accurately.
Reassemble the spring and lower clevis. Job done.
![]()
Those cheap eBay RFY shocks are very tempting for a vintage build for around $100 a set. But, right out of the box, they are absolute garbage. They are sure to be under filled with oil and Nitrogen. Generally, they will be about 100cc low on oil and the N2 charge is very inconsistent. I have found that the N2 pressure can be anywhere between 15 psi to 40 psi. They should be around 75 psi.
In spite of all the disparaging comments about these shocks, they can be made to work reasonably well, though. Once modified and rebuilt correctly, they have plenty of rebound damping but the compression damping is a bit light. I have, yet, to figure a way to increase that, but the spring rate compensates pretty good for compression so it is not much of an issue.
Watch this tutorial, as it very closely resembles the process needed to rebuild the RFY shocks.
Now, watch it again!
EDIT: That video has been removed. I made my own video and a link is posted later in the thread, in post #13.
OK, now you are ready to proceed.
The tools needed to perform the rebuild are pretty cheap and can be made with a bit of ingenuity. You will need a vise with Aluminum soft jaws, a spanner wrench....I bought an adjustable spanner, but the one for an angle grinder works. You will also need to fab up a spring compressor if you don't have one. and you will need a piece of steel tubing (I think you need 1.5" diameter, I don't recall exactly though) . I had pieces of an old porch swing in my scrap pile that I cut up.
First, to fab up a spring compressor, you'll need a piece of flat stock with a slot in it and a hole drilled. I had a couple of piston holders in my tool box that already had a slot, (that had to be widened, slightly), and I had to drill the hole.
Next, a vise, a 1/2" bolt, some long eye bolts, nuts and washers, and here is my spring compressor:
Once you have the spring off, it is very apparent that the shock is not completely full. Cycle the shaft a few times, and you can feel and hear the air in the system.
Remove the valve stem core from the valve stem in the N2 reservoir and use a socket and and a dead blow hammer to push the reservoir down enough to remove the spring clip retainer that keeps the reservoir cap in the reservoir. Use compressed air applied to the valve stem to force the cap and bladder out of the reservoir. DO NOT try to pull it out by the valve stem. Once the res cap is removed, you can dump the oil out of the reservoir, at this point.
Next, set the shock up in in the vise and remove the shock seal retaining cap with the spanner. Use A section of pipe between the the pre-load adjustment ring and the spring retainer, with a washer (or two) and the jam nut for the lower clevis, and use an impact wrench to pull the shock shaft out of the shock body. Below is a picture of my home made puller. The pipe I used is a section from an old porch swing I had in a scrap pile.
Here's everything disassembled:
- - - Updated - - -
Now for assembly:
One of the reasons that these shocks are not completely full is that the seal is 15 mm high, and there is no way to install it without trapping air in the body. The original seal is at the top.
Another reason, I am sure, is the QA control at the factory. We are addressing the QA issue by doing the rebuild, but the seal issue has to be addressed, as well. There is a boss at the top of the shock, that looks like it should have an damping adjuster. I paid a local machinist a few bucks to spot face the boss to house an o-ring, and drill and tap a hole for a bleed screw. I used a button head 10-24 Allen screw and an o-ring for the bleed screw. Install the screw and o-ring.
Following the video in the previous post for assembly, Fill the shock body with fork oil (I used 10 wt, but you may need to play with oil weight). Insert the reservoir cap with the bladder. Tap it in past the spring clip ring and install the spring clip and install the valve stem core. Next, bump a bit of air in the reservoir and the cap should seat against the spring clip.
If you are going to replace the seal, good luck! I have not found a vendor that sells the 12.5 mm x 32 mm x 15 mm seal. I did find a SKF 12 x 32 x 7 mm seal, and decided to stack two of them in each shock.
Note: It is advisable to cut a flat piece of thin plastic and wrap it around the threaded portion of the shock shaft to avoid damaging the seal.
Install the shock shaft, being careful not to displace the white teflon bushing. It is prone to moving out of its groove. Using the plastic guide method when installing the shaft is a good idea, here, as well.
Give the end of the shock shaft a few good whacks (to drive air out of the shim stack), and let the air bubble to the surface. Do that a couple of times, and let it sit for a few minutes. Top off the oil.
Place the seal (or seals ) flush with the rim of the shock body and release the air from the reservoir, while pushing the seal into the body. It should draw the seal in. You might need to tap the seal in a little farther. All you need is for it to be in far enough that you can catch a thread with the shock body retainer cap. Use your spanner wrench to tighten up the retainer cap.
Flip the shock right side up and cycle the shock shaft to get any air to the top of the shock. Once there is no air in the shim stack, use the bleed screw to get the rest of the air out and use a syringe or something to top off the shock. Replace the bleed screw and o-ring.
Now, you need to get it filled with 75 psi of N2. In a pinch, a tire shop that has Nitrogen can do it, but their equipment is made to fill tires....and quickly. It is much more advisable to find a shop that does suspension work. (A motorcycle suspension shop, an off road truck specialty shop, a local speed shop maybe) Their equipment will include a feed valve that fills slowly and accurately.
Reassemble the spring and lower clevis. Job done.
