This may be a dumb question but I have never run into this before. I have an 81 Miyata 1000 with a suntour cyclone derailer, 5 speed freewheel and suntour barcons. The issue is that while riding it will not shift into the highest gear (smallest sprocket). When I put the bike on the repair stand it will shift into the highest gear. I made a few adjustments but get the same results. It's got me dumbfounded, but that's not too hard for me.

Mutt

what adjustments have you made? It's probably a simple case of tweaking a limit screw. It may also help to move the axle's position in the dropout. When you let the shifter out all the way (to top gear), is the cable entirely slack?

you might want to cross-post this, or just move it to the bicycle mechanics forum

-rob

Yeah my adjustments were with the limit screws. I didn't think about the axle not being straight. That will be on the to do list tomorrow.

Thx
Mutt

not just straight, but the position fore and aft makes a difference in the angles at which the cage sits. i can't recall if you're problem may be a result of it being too far forward, or too far backwards, but you ought to experiment some...

-rob

This is not too unusual. Question 1: with the derailleur in the small cog, is the cable taught? if yes, then the backing out of the limit screw may not have any effect because the cable won't let it move.

If not, it might be helped by the "B-screw" on the back of the derailleur which will impact how the chain enguages the freewheel. This would be unusual. Your cable may also be corroded such that it is not sliding smoothly. Worst case, you simply need to back out the limit screw such that the derailleur appears to slightly overshift (towards the dropout).

does your cyclone have a b-screw? if so, you can semi-ignore my advice about repositioning the axle in the drop-outs. iirc, the very early cyclones had no b-screws, but they ended up getting them later? I wish i had one on hand to take a closer look... (of course, there's several iterations/variations of cyclone RDs anyway.

-rob

Yes it does have a B screw. The part I don't understand is that it will shift into the highest gear on the stand but not when I'm riding it. Anyway I'll try adjusting the B screw tomorrow. I may replace the cables also.

Thanks,
Mutt

Yeah, I had one of these weird derailler non-shift problems on a 10 speed, it turned out to be a kinked cable.

i had a similar problem recently and it was simply a gummed up derailleur that needed a bit of cleaning.

Does anything move or flex when you put weight on the back wheel? Like, if you have loose-ball hubs, and your bearings are too loose, you could have sideways movement that could affect shifting. Or if you have too much frame flex for some reason. Or a broken axle.

Other possibilities:

- cable too tight (as suggested already)
- too much side-to-side play in the RD (but a little bit of play is normal, and not a problem, in my experience): one of the pivots could be worn, or loose (unlikely, but possible), or the upper jocky wheel could be worn or loose.
- too much side-to-side play in the freewheel, if it's been ridden in dirt and wet a lot

A good cleaning of the RD and the freewheel cogs would be a good place to start. And if you haven't replaced the cable (and maybe the housing), that couldn't hurt.

I say it's sticky. If you let up the pressure or even backpedal while riding and trying to shift into the smallest cog, does it work?

For the record, I have a Cyclone that is date coded October 1975 which would place it as the first year of production. It does have a B-adjustment screw.

Easiest place to start is to shift the bike into it's high gear while it is on the stand and release the cable from the derailleur to check it's tension as the Cyclone does not have a barrel adjuster... you don't have to remove it but just loosen the pinch nut.

Check the position of the derailleur to make sure it is lined up and straight and if this is the case, shift the derailleur manually (by pushing it sideways) when you are turning the cranks to make sure it drops back down into high gear.

If it does this without the cable attached and the problem recurs when you put everything back together then you need to check the cable housings, shifter, and routing under the bottom bracket.

The guide under the bb can get very dirty and prevent the cable from moving smoothly... and if the cable that leaves the Barcon has poorly finished ends the cable could also be hanging up here or there may be a problem in the cable housings themselves.

Dropout derailleur hanger straight - as in aligned perfectly parallel in the frame? You cannot really accurately tell by just looking. And even if the dropouts are parallel the hanger may be bent. This could effect shifting, especially when chain is under torque but not noticed when on a repair stand.

Park makes a simple tool which any bike shop should have. It just threads into the derailleur hanger and then you manually check the gauge at different points around the rear wheel rim to make sure the derailleur hanger is not bent fore-or-aft or down-or-up. If anything is tilting off, the gauge is then used as an alignment tool - just pushed or pulled gently - until everything is set just right. Takes all of about 5 minutes for someone to check and/or adjust anything.

... Also, even a "wobble" in an old worn freewheel could cause problems when shifting...

... Bent or worn derailleur or derailleur cage...

The Good news is that this issue is common and never a serious problem to remedy, whatever the cause. Those are Great bikes. They were also made to tackle heavy loads and this factor can always amplify any unseen wear issues on even less frequently ridden bikes. Just try making the simplest and least costly adjustments first.

Good Luck!

Well thanks for all the help. I got the problem fixed. I wound up just taking the derailleur off. I think it was slightly bent so I fixed that and cleaned and de-gunked the derailleur. I put it back on the bike, made my adjustments and everything works great and the Miyata is back on the road.
Sixty Fiver, I wish I had read your post before I took everything off. Putting that cable back through the derailleur was a pain in the butt.

Thanks for the help everyone
Mutt

thank you for the info and, i have to say, that's a delicious pic of your derailer. I'm totally jealous. My cyclone is...homely. (With a b-screw, too)

-rob

Good to hear.

That pretty cable routing comes at a cost... but once you do it a few times it gets easier.

The Mk2 is a little harder to route cable through than the Mk1 and when I am installing them I remove the derailleur to thread the cable through and then tighten the cable once it is back on the bike. Trying to reinstall a used cable in a Cyclone can be very hard as any stray wire end will makes things really hard.

These are good candidates for the use of soldered cable ends.

Tell me about it. It was a bear to get that cable back through there again. You've got a great idea to thread it then put it on the bike. I wish I had thought of that, lol. I guess that's the difference between a pro and an amateur, lol.

Mutt