Cafe Racer Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
1,536 Posts
Discussion Starter #1 (Edited)
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.


IMG_3143.JPG


Watch this tutorial, as it very closely resembles the process needed to rebuild the RFY shocks.




Now, watch it again!




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.


IMG_5601.JPG


Next, a vise, a 1/2" bolt, some long eye bolts, nuts and washers, and here is my spring compressor:


IMG_5635.JPG


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.


IMG_3150.JPG


Here's everything disassembled:
IMG_3148.JPG

- - - 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.
IMG_5632.JPG


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.


IMG_3154.JPG IMG_5629.JPG


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.


IMG_5633.JPG


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.


IMG_5637.JPG
 

Attachments

·
Registered
Joined
·
1,536 Posts
Discussion Starter #2
And Tanshanomi's response is worth quoting. CrazyPJ machined the lowers on his because the ones with the lower clevis arrangement (as opposed to the eyelet lower mount) are weak and tend to snap as the mounting bolt tends to squeeze the clevis legs together:

One other thing to watch for with RFY shocks and
their bretheren is the lower mount stripping/breaking. This is one guy's solution:




I got it from here:
http://forums.sohc4.net/index.php?topic=76385.25
but in one post he references a more extensive thread on DTT.
 

·
Registered
Joined
·
840 Posts
The hardest part is figuring out how to hole the shock in a milling machine to spot face and drill for the bleeder screw. I used screws with built in O-rings in mine from McMaster-Carr. McMaster-Carr
I used 1/4 so I could screw in a taller center drilled screw (stand pipe) I had planed on using a 5mm and a adapter from my mercury sticks but the hole is so small its hard for the oil / air mix to float up the tube.
Also hooking up a hand pump vac to the bladder with the valve stem out and pulsing it helps jiggle out the air along with moving the shaft.
 

·
Registered
Joined
·
10,450 Posts
Very cool to see what goes into rebuilding these.
 

·
Registered
Joined
·
88 Posts
Very cool to see what goes into rebuilding these.
I tried RFY's on my RD 350 but they were way too stiffly sprung for a 290lb bike with 150lb rider even at minimum preload. I switched to Hagons from Dave Quinn which work great with .85 RaceTech forks.
I ended up selling the RFY's at half price to a guy who planned to rebuild them. The RFY's do have nice machining & finish.

Jim B
 

·
Registered
Joined
·
840 Posts

·
Registered
Joined
·
7 Posts
Hi! Great post! I am about to rebuild my own shocks or atleast change oils of the shocks. There seems to be some video in the post but it's not awailable. Is there anyway to see that video? Don't know the exact amout of oil and how to properly disassemble the shock without damaging them! Thanks!
 

·
Registered
Joined
·
5,622 Posts
Hi! Great post! I am about to rebuild my own shocks or atleast change oils of the shocks. There seems to be some video in the post but it's not awailable. Is there anyway to see that video? Don't know the exact amout of oil and how to properly disassemble the shock without damaging them! Thanks!
Hey Tupezzi, you might as well post new posts as add on to ancient ones on this site, it just moved.

I seen a picture of a chinese rear shock absorber that was broken a couple weeks ago, you know the big steel cylindrical part on the back of the shock that has the nitrogen reservoir in it? Well the nitrogen reservoir broke clear off that thing and guess what was inside :| nothing, no holes for anything it is just a big lump of powdered metal to make it look like a nitrogen gas reservoir shock absorber. It's at best a spring holder.
 

·
Registered
Joined
·
23,296 Posts
I seen a picture of a chinese rear shock absorber that was broken a couple weeks ago, you know the big steel cylindrical part on the back of the shock that has the nitrogen reservoir in it? Well the nitrogen reservoir broke clear off that thing and guess what was inside :| nothing, no holes for anything it is just a big lump of powdered metal to make it look like a nitrogen gas reservoir shock absorber. It's at best a spring holder.
That wasn't an RFY branded shock, but something else. Could have even been a counterfeit RFY (strange I know).

RFY isn't exactly a bad shock, it's just a budget scooter shock built to a cheap price point that is being used for applications they weren't intended for with various degrees of success and failure. The biggest issue with RFY is quality control, which also happens to be the biggest area of savings for the makes of auto/motorcycle parts. It's important to take them apart because it could have inadequate fluid or broken parts inside.


Hi! Great post! I am about to rebuild my own shocks or atleast change oils of the shocks. There seems to be some video in the post but it's not awailable. Is there anyway to see that video? Don't know the exact amout of oil and how to properly disassemble the shock without damaging them! Thanks!
Go search on youtube, there are a few tutorials on everything from rebuilding to adjusting preload. I think thats where the original videos were as well.

If you haven't been here, this is a good source of info:

 

·
Registered
Joined
·
7 Posts
I started today ny disassembling the shocks and immediately saw somethings wrong with other shock. When i relealed the n2 from the reservoir it started to spray oil from there. When i disassembled the reservoir i saw there is a big hole in the bladder... Is there any bladders as an spare part wich will fit straigt to the reservoir?
 

·
Registered
Joined
·
1,598 Posts
I started today ny disassembling the shocks and immediately saw somethings wrong with other shock. When i relealed the n2 from the reservoir it started to spray oil from there. When i disassembled the reservoir i saw there is a big hole in the bladder... Is there any bladders as an spare part wich will fit straigt to the reservoir?
You should start a new thread for your work, this one is complete with only 8Balls tutorial.
 

·
Registered
Joined
·
1,536 Posts
Discussion Starter #12
Hi! Great post! I am about to rebuild my own shocks or atleast change oils of the shocks. There seems to be some video in the post but it's not awailable. Is there anyway to see that video? Don't know the exact amout of oil and how to properly disassemble the shock without damaging them! Thanks!
Apparently that video was taken down, or moved. The first 5 minutes and the last 5 minutes of this video are close. I wouldn't use the Schraeder valve to pull the reservoir end cap on these shocks, though. A quick shot of air into the Schrader should pop the cap out with the bladder.

As far as oil quantity: You don't want ANY air in the oil side of the shock. 1 quart of oil should be plenty. So what ever it takes to fill it completely. And putting a bleed screw in the top is HIGHLY recommended, so you can get all the air out.
 
1 - 12 of 12 Posts
Top