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Old 02-18-11, 10:05 AM   #1
vinfix
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Suntour Cyclone RD, can't adjust it from 7 spd to 6 spd?

I have a Suntour Cyclone MKII RD, which supposedly is able to handle up to 32T on my Vitus. It was working well with a no-name 7 speed freewheel with (I think) 28T as the biggest, and a KMC Z-chain, and Campy friction shifter.

As an experiment I tried a 6 speed Shimano "corn-cob", which only goes up to 20T. Strangely, I can't get it to shift onto the 20T, and I'm out of adjustment! This does not make sense to me since I know it can handle the range. What am I missing?
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Old 02-18-11, 10:12 AM   #2
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Off the cuff, did you check your B screw as well as limiter(s)?
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Old 02-18-11, 10:17 AM   #3
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Is this on the same wheel or a different one with a different hub? I wonder if there is a difference in the placement of the freewheel in relation to the dropout that may be the issue.
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Old 02-18-11, 10:38 AM   #4
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Is this on the same wheel or a different one with a different hub? I wonder if there is a difference in the placement of the freewheel in relation to the dropout that may be the issue.
+1, that's about all that makes sense...the other end I could see there being differences...but not on the hub side.

OP are there any ring spacers on the hub?
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Old 02-18-11, 10:59 AM   #5
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Same wheel, didn't change spacing. The 6 speed is a narrower stack. The Cyclone has only 3 screws, L, H, and the chain wrap, which I dialed all the way in. The chain just doesn't make enough of an angle going in to pick up the sprocket, just chatters.
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Old 02-18-11, 11:31 AM   #6
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Sorry but it's not clear that you did try the limit screw? As mentioned, the freewheel body may have a different relative position. If your freewheel is a Suntour Ultra, they have a history of being fussy with some chains.
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Old 02-18-11, 11:41 AM   #7
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Sounds like chain is too flexible for the increased chain gap caused by the smaller large cog. B-screw should be dialed out, as opposed to in, for this problem.
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Old 02-18-11, 12:01 PM   #8
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Sounds like chain is too flexible for the increased chain gap caused by the smaller large cog. B-screw should be dialed out, as opposed to in, for this problem.
That's interesting...so taking a link (or 2) out of the chain might add enough tension to enable the shift.
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Old 02-18-11, 12:35 PM   #9
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Yeah, that was going to be my next suggestion - taking a link or two out of the chain. if you've got it on a stand, you could manually push back on the derailleur to mimic adding tension / adjusting the B-limit while turning the cranks to see if that solves the problem, or slide the wheel forward in the dropouts to do roughly the same.
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Old 02-18-11, 02:43 PM   #10
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Thanks,I'll try the B-limit the other way (vertical drop-out on this bike, no adjustment). I already have the L limit fully out. The purpose of the experiment is to see if I can eliminate auto-shifting I get under certain conditions. The narrower, 6 speed looks like it will have a straighter chain line, which should help. I also have a wider Nashbar 6 speed freewheel to try.
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