Chain Kept Falling Off, I Tinkered With The Bike Too Much..



Uawadall said:
It won't shift into the big ring while tugging it.
Loosen the high limit screw (the one on the outside) and try it again. We're seeing if the problem is the derailleur. If you can shift by just pulling the cable, then we know the problem isn't the derailleur. It's upstream--the lever or a section of cable between the lever and where you're pulling.
 
oldbobcat said:
Loosen the high limit screw (the one on the outside) and try it again. We're seeing if the problem is the derailleur. If you can shift by just pulling the cable, then we know the problem isn't the derailleur. It's upstream--the lever or a section of cable between the lever and where you're pulling.
I removed the high limit screw and it will shift into the higher gear. Its stiff and it clanks(when changing gear), but the derailleur is functioning. When I lower the screw to the point that it touches the inside of the derailleur, it will no longer shift.
 
Uawadall said:
I removed the high limit screw and it will shift into the higher gear. Its stiff and it clanks(when changing gear), but the derailleur is functioning. When I lower the screw to the point that it touches the inside of the derailleur, it will no longer shift.
We're getting somewhere. Put the limit screw back in so you don't lose it. The high limit screw should only touch the inside of the derailleur when the chain is on the big ring. It's there to keep the derailleur from throwing it over the top. Don't bother with adjusting it now. Just screw it back into the hole so it doesn't fall out.

So we know the derailleur works. Is it positioned right? The outer plate should be parallel to the chain rings and it should clear the teeth on the big ring by 1-2 mm.

After getting that sorted we're going to test the shifter and cable. Pulling on the end of the cable with one hand, do some upshifts (the brake lever) and downshifts (the paddle). Can you feel the cable tightening and loosening? Does the action feel reasonably light and crisp? Report back.
 
oldbobcat said:
We're getting somewhere. Put the limit screw back in so you don't lose it. The high limit screw should only touch the inside of the derailleur when the chain is on the big ring. It's there to keep the derailleur from throwing it over the top. Don't bother with adjusting it now. Just screw it back into the hole so it doesn't fall out.

So we know the derailleur works. Is it positioned right? The outer plate should be parallel to the chain rings and it should clear the teeth on the big ring by 1-2 mm.

After getting that sorted we're going to test the shifter and cable. Pulling on the end of the cable with one hand, do some upshifts (the brake lever) and downshifts (the paddle). Can you feel the cable tightening and loosening? Does the action feel reasonably light and crisp? Report back.
I figured out the last bit about tension a day ago by trial and error. The high limit screw is barely in(just enough that I don't lose it). The bike now can shift without clanking or the chain from falling off except in one gear combination. If its in the big ring in the front and highest(biggest diameter) cassette in the back, the chain will fall off every time and very easily. I'm afraid to mess with the limit screws too much, they're getting kind of stripped.
 
Uawadall said:
I figured out the last bit about tension a day ago by trial and error. The high limit screw is barely in(just enough that I don't lose it). The bike now can shift without clanking or the chain from falling off except in one gear combination. If its in the big ring in the front and highest(biggest diameter) cassette in the back, the chain will fall off every time and very easily. I'm afraid to mess with the limit screws too much, they're getting kind of stripped.
Take it to a shop. This is going to take some time and first-hand expertise (and now, a little more money) to unravel. Good luck.
 
oldbobcat said:
Take it to a shop. This is going to take some time and first-hand expertise (and now, a little more money) to unravel. Good luck.
Its not "new bike" or mech tune up smooth, but it isn't rough and clanking either.I've got everything functioning and shifting into every gear. Thanks everyone for the assistance, I'm no bike mechanic, but have learned enough not to be afraid to take a tool to the bike. This will be enough for now.
 
You're welcome. The hard part of learning maintenance on a secondhand bike is not having a baseline of how things are supposed to work as the manufacturers intended. As a shop mechanic, I see countless mickey-mouse solutions to problems that would have gone away if the components were simply installed and adjusted according to spec.
 

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