Bob Ross

I've got a SunTour Cyclone rear derailleur w/ a six-speed freewheel on my 23-year-old Bridgestone 600.

Lately whenever I backpedal the chain dumps off the upper jockey wheel towards the inside. It doesn't actually get stuck between the jockey wheel & the cage, it still moves freely, but it makes a hellacious racket, plus of course it totally screws up the efficiency of the drivetrain.

Any ideas what might be causing this?

In the past I've noticed while cleaning my chain that the rd would sometimes swing forward when I backpedalled, as if the chain was somehow not moving freely through the cage & instead was tugging on the rd...this would happen when I was gripping the chain w/ a rag. So now it would seem there's some sort of tension/load on the chain during normal operation? Or something like that...?

My wife says "Just don't backpedal." Thanks, honey.

Other suggestions appreciated.

demoncyclist

Clean/replace chain and jockey wheels. Oh, and don't backpedal- there is absolutely no reason to ever do this.

Retro Grouch 

Backpedal the bike slowly with your hand while you watch the chain run across the jockey pulleys. If you find a single link that sticks up, it's tight. Loosen it with a chain tool or by twisting the chain sideways with your hands.

tellyho

How much freewheel wobble do you have? If that's worn enough, it could cause jumping. Unlikely, I know.

Pull your sprockets, clean and lube. Lube your chain and check for stiff links as above.

See if the derailleur hanger is straight. I doubt this is the problem, as you don't report shifting issues.

Bob Ross

I know I should be grateful for any advice I can find, since it's a seller's market

...but I can't just let that comment go.

Exactly how would you propose a cyclist on a geared bike w/ a freewheel or freehub deal with stopping & starting at traffic lights without backpedalling?

Are you suggesting they somehow unclip while their pedal is in the ~2:00 position so that subsequent starting is effortless (which would require holding the still clipped-in pedal up against the force of gravity)? Or are you suggesting they start up with their pedal in some sub-optimal position? or that they use a "scooter start/dog paddle" technique? Should they all be doing trackstands? Or should they be lifting their back wheel off the ground once stopped and doing a one-legged 270° with their clipped-in foot in order to bring the free pedal to the ~2:00 position?

I'm very curious.

raleighrider75

Is the derailleur bent?Sitting at a slight angle?
As for not back pedalling,that's just absurd.There will always be a time when you need to.