Suntour Cyclone mkII return spring issue
06-08-12, 04:09 PM
#1
enginerd
Thread Starter
Suntour Cyclone mkII return spring issue
I've got a Cyclone mkII rear der mated to some "Symmetric" shifters that won't go into the smallest rear cog. I've backed the limit screw out but the der just won't return to the full relaxed position, even with the cable fully slack. Is there a way to adjust the spring tension without taking it apart? I know there's a wound spring inside the big pivot with the hex key bolt. There's a tiny flathead screw inside the hex recess but it won't budge. Any thoughts? Is it just too tired?
06-08-12, 05:54 PM
#2
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If you haven't done so yet, Try cleaning (dip it in some minearal spirits for a little while and hit it at the hinge areas with brushes) the RD really good and relubing it. It might just be old, stiff contaminated grease keeping it from smoothly/easily going through it's full shifting arc. If that does not work it might be a worn out return spring. I'm not sure if you can easily replace those on a MkII. Maybe you can try shimming it up where it contacts the parallelogram arm(s) as a last resort to add in some more spring tension, but be careful doing so as putting materials in that area might further limit the RD shifting stroke too.
Chombi
Chombi
Last edited by Chombi; 06-09-12 at 08:04 PM.
06-08-12, 08:04 PM
#3
Senior Member
I have the successor to that model, the first gen XC. I had the same problem, the return spring isn't strong enough to return the cage all the way to high gear. I wonder if this was a general problem with Suntours?
06-08-12, 10:57 PM
#4
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On a Mk. II it's pretty easy to remove/replace/retension the return spring. That's not a small straight-head screw, that's the slot that one end of the return spring passes through. You'll have to disassemble the main pivot.
Use a Phillips screwdriver to remove the stop pin from the pulley cage, gently release the tension by letting the pulley cage unwind. Then remove the outer pivot bushing (5mm? 6mm? hex bolt with the plastic around the edge). After that the pulley cage will slide right out. Don't lose the little shim from the slot the spring goes through on the pulley cage pivot pin.
You probably don't need to add more tension -- once it's disassembled just clean all the gunk out and lube the spring and bushing with light oil. Then reassemble. Friction takes up a ton of the spring power on these derailleurs once they're all nasty and gunked-up.
Unfortunately you can only add additional tension 1/2 turn at a time, due to the design of the spring attachment points. So, hope you don't need to.
Use a Phillips screwdriver to remove the stop pin from the pulley cage, gently release the tension by letting the pulley cage unwind. Then remove the outer pivot bushing (5mm? 6mm? hex bolt with the plastic around the edge). After that the pulley cage will slide right out. Don't lose the little shim from the slot the spring goes through on the pulley cage pivot pin.
You probably don't need to add more tension -- once it's disassembled just clean all the gunk out and lube the spring and bushing with light oil. Then reassemble. Friction takes up a ton of the spring power on these derailleurs once they're all nasty and gunked-up.
Unfortunately you can only add additional tension 1/2 turn at a time, due to the design of the spring attachment points. So, hope you don't need to.
06-09-12, 01:28 PM
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I don't think the OP is having a problem with the cage tension spring, but has a weakened parallelogram spring that is non-serviceable.
Chombi makes a good point about the possibility of putting some kind of shim material inside of the parallelogram to boost (pre-load) the twisting force of the spring.
Suntour also had problems with their enclosed-body derailers of similar vintage having to do with spring failure.
Assuming here that the OP has backed off the correct (hi-limit) screw?
Chombi makes a good point about the possibility of putting some kind of shim material inside of the parallelogram to boost (pre-load) the twisting force of the spring.
Suntour also had problems with their enclosed-body derailers of similar vintage having to do with spring failure.
Assuming here that the OP has backed off the correct (hi-limit) screw?
06-09-12, 01:38 PM
#6
enginerd
Thread Starter
yes, it's the parallelogram spring. I've backed the hi limit screw out, and I can pull the der out by hand to get it into the smallest gear but it won't shift there on its own. it might just be worn out.
06-09-12, 01:52 PM
#7
The Left Coast, USA
Is the cable connected at all? I ask because I went crazy with an RD until I found the cable was frayed inside the jacket behind the RD, it seriously messed up the back swing...and I though tthe RD was a goner Just something to rule out.
06-09-12, 04:05 PM
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Another good point here, how much tension is available with the cable removed? It then may point to using new cables and housing to reduce friction to an absolute minimum along the entire run, but especially that troublesome section in back that caused FrenchFit's problem.
GripShift (SRAM) even made a booster spring that acted on the cable itself, just ahead of the rear housing. It consisted of a rubber bellows that you tensioned with a collar with a set screw, so it sealed the opening AND added some return force to the cable since Shimano's newest (at the time) derailers had very light return springs in the parallelogram. They called it a BassWorm, sold alongside their superior "JonniSnot" shifter/cable lubricant. Good stuff, that lube, I have found nothing better for the plastic-on-metal interaction between cables and lined housings.
