Suntour Edge 4050 overhaul
01-16-18 | 08:55 AM
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From: Near Pottstown, PA: 30 miles NW of Philadelphia
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Suntour Edge 4050 overhaul
I recently cleaned up a Suntour Edge 4050 rear derailleur and was pretty stumped on how to take it apart to service the body spring. I found NO information out in the cloud on these but did figure it out (played the old game "what if I try this? Nope, try that."). So "you may know somebody in a similar situation, or you may be in a similar situation, and if your in a situation like that...." these photos and experience may be useful. This may even apply to other late model (circa late '80s) Suntour RDs. BTW: I had to take this RD apart as the cage pivot would not move - the original grease and grime had glued the spring and rotating shaft in place. Only concerted force would rotate the cage which would, then, not return. I could have tried to hose it out with WD40 or MS but that would not have been right. I wanted to clean it out and relube with fresh grease and apply thread lock.
Taking the cage apart and cleaning out the jockey wheels was straight forward so I'll not explain. The problem was how to get the cage and top wheel shaft out of the RD body. I removed the rotation stop screw which allowed the cage to 'unwind". Mine rotated CW about 180 degrees to that shown in the first phots.
https://www.bikeforums.net/images/attach/jpg.gif
The green arrow shows the threaded whole where the stop screw was. I recommend you never force that screw out - be gentle and give it time, penetrating oil and the right screw driver bit. I have a pretty large selection of driver bits so I can try several (whether straight or 'philips') to ensure that I'm using the best fit driver. Too easy to damage the stop screw which has been tightened in there for 30 or 40 years. This goes for most screws on old bikes. Take the time to lube the threads, let them soak, pick the perfectly fitting driver then give em some gentle torque until they move.
With the cage assembly fully unwound it still will not come out. I found (see the next photo) that the end of the rotation shaft has a flat - a D shaped end (red arrow). That engages with a pin that is down at the end of the cylinder inside the RD body (very hard to see but follow the blue arrow). Rotate the cage assembly back and forth a bit until that D is lined up with the pin and it then slides apart. Easy. The pin captures the shaft as the D is not normally lined up right. The third photo is a different angle so you can see that you'll find when you get it apart. This RD was all cleaned up prior to the photos though. When this one came apart, the internals (spring and shaft) were coated with dried, black old grease.
https://www.bikeforums.net/images/attach/jpg.gif
https://www.bikeforums.net/images/attach/jpg.gif
You'll also see the body spring there in the snaps. In the second photo, see where there is one hole in black plastic shield on the cage rotation shaft. Moving that shield will align that hole with 2 or 3 choices on the cage body. There are also 2 holes in the bottom of the RD body well. Those holes accept the ends fo the body spring when assembled. That gives you several choices for spring tension - whatever works best for your bike: FW and chain ring size, chain stay length and axle position in the drops. Find one what works best for you. Probably take some trial and error. I found that the 'tangs' on the two ends of the spring were not the same length. I put the shorter tang in the cage body hole so it would not protrude on the other side of the hole and impact the cage rotation.
Assembly is the opposite of disassembly. Those familiar with these RDs will know that the 'nut' for the shaft end of the top jockey wheel is unusual. Not a hex but a round, threaded nut with two notches in the outside edge. For the overhaul of another Suntour RD I made a 'tool'. I have snap ring pliers with multiple bits. I took a pair and ground the tips to fit those two notches. I install them in the snap ring pliers then fit all that in to those two notches and can turn that 'nut'. On reassembly I use a wee bit of blue locktite to keep that nut in place. If it vibrates out there will be 'the devil to pay' finding another one.
Yes, I cleaned up the rest of the RD after I got the rotation assembly sorted out. Take care of the show stoppers, the death knell problems first. Then do the easy stuff.
Taking the cage apart and cleaning out the jockey wheels was straight forward so I'll not explain. The problem was how to get the cage and top wheel shaft out of the RD body. I removed the rotation stop screw which allowed the cage to 'unwind". Mine rotated CW about 180 degrees to that shown in the first phots.
https://www.bikeforums.net/images/attach/jpg.gif
The green arrow shows the threaded whole where the stop screw was. I recommend you never force that screw out - be gentle and give it time, penetrating oil and the right screw driver bit. I have a pretty large selection of driver bits so I can try several (whether straight or 'philips') to ensure that I'm using the best fit driver. Too easy to damage the stop screw which has been tightened in there for 30 or 40 years. This goes for most screws on old bikes. Take the time to lube the threads, let them soak, pick the perfectly fitting driver then give em some gentle torque until they move.
With the cage assembly fully unwound it still will not come out. I found (see the next photo) that the end of the rotation shaft has a flat - a D shaped end (red arrow). That engages with a pin that is down at the end of the cylinder inside the RD body (very hard to see but follow the blue arrow). Rotate the cage assembly back and forth a bit until that D is lined up with the pin and it then slides apart. Easy. The pin captures the shaft as the D is not normally lined up right. The third photo is a different angle so you can see that you'll find when you get it apart. This RD was all cleaned up prior to the photos though. When this one came apart, the internals (spring and shaft) were coated with dried, black old grease.
https://www.bikeforums.net/images/attach/jpg.gif
https://www.bikeforums.net/images/attach/jpg.gif
You'll also see the body spring there in the snaps. In the second photo, see where there is one hole in black plastic shield on the cage rotation shaft. Moving that shield will align that hole with 2 or 3 choices on the cage body. There are also 2 holes in the bottom of the RD body well. Those holes accept the ends fo the body spring when assembled. That gives you several choices for spring tension - whatever works best for your bike: FW and chain ring size, chain stay length and axle position in the drops. Find one what works best for you. Probably take some trial and error. I found that the 'tangs' on the two ends of the spring were not the same length. I put the shorter tang in the cage body hole so it would not protrude on the other side of the hole and impact the cage rotation.
Assembly is the opposite of disassembly. Those familiar with these RDs will know that the 'nut' for the shaft end of the top jockey wheel is unusual. Not a hex but a round, threaded nut with two notches in the outside edge. For the overhaul of another Suntour RD I made a 'tool'. I have snap ring pliers with multiple bits. I took a pair and ground the tips to fit those two notches. I install them in the snap ring pliers then fit all that in to those two notches and can turn that 'nut'. On reassembly I use a wee bit of blue locktite to keep that nut in place. If it vibrates out there will be 'the devil to pay' finding another one.
Yes, I cleaned up the rest of the RD after I got the rotation assembly sorted out. Take care of the show stoppers, the death knell problems first. Then do the easy stuff.
