Vinnems

Though I think this is just an issue with the lever. Whenever I shift, it works its way back to... I don't know what gear it is, but the lever will be pointing up towards the top tube. I push the lever down and shift, then it works its way back up and shifts through all the gears. It's a Shimano SIS, I believe. Here's some pics.


I just got this bike, which is perfect in every way except this. I was playing with the derailleur lever, which has a screw I can tighten and a little metal tab I can turn to a little bit in one direction and then back. I tighten the screw and it holds, but after a few shifts in gets loose. I can't turn the metal tab at all after tightening the screw, but can when it's loose, but that doesn't seem to do anything.
Any help is appreciated. Thanks!
EDIT: The bike is a 1987 Centurion with Shimano 600 components all around.

JohnDThompson 

You need to tighten the lever up so it doesn't slip. Use a screwdriver in the slot on the lever mounting bolt. Tighten it just enough so that it doesn't slip; too tight and you'll have trouble moving the lever to shift gears. If you want indexed shifting, grab the loop and turn it so the red arrow points to "SIS" on the lever body. If you want friction shifting, turn it so the arrow points to "FRICTION."

Andrew R Stewart 

It also looks like, in photo 2, that the rear der is either miss mounted or it's upper pivot spring is broken. typically the der "hangs'" (odd to use this term when the bike's upside down) with the unit swung rearward. There's a spring in the upper pivot (the one that has the mounting bolt running through it) that does this. If the tab on the upper pivot/mounting bolt assembly is not behind the matching tang on the drop out (or hanger) then this spring won't pull the der back. If the tab and tang are properly engaged then this upper spring might be broken or it's ends are not internally positioned in their little holes. Either way if this upper pivot is not pulling the der back properly the upper pulley (the guide pulley) will run up against the cogs and shifting will suffer a lot. Andy.

Andrew R Stewart 

On looking at the photo again i see that the chain is routed onto the chain stay chain peg. This tension on the chain could explain why the der is pivoted so far forward. Andy.

Vinnems

Thanks John, I'll try that when I get home and hope it works. Did a little research and found that apparently these shifters don't last too long, and if this is the original in might be broken already. Something about teeth on it that break over time. I'll see if tightening it works and if not, I'll pull it apart.
And don't worry Andrew, the derailleur itself is fine I just have the chain on the peg to keep it from hanging all over.

Vinnems

I tried what you said, John, but no matter what, when working the lever, the bolt would always come loose. I took it apart and all the teeth fell out, as pictured:

Should this still work as just a friction shifter, or is the whole thing toast? I don't really care about index shifting, as friction is what I'm used to.
Worst case scenario, what can I use for a replacement? The cassette is 6 speed.

rccardr 

If that won't stay tight as a friction shifter, Shimano 105 (1050 series) shifters seem to be more durable and would be a direct bolt on replacement.

Beware of prior model Shimano 600 6207 friction only shifters, as they used a different and proprietary Shimano specific base mount that is not compatible with the later 6208 (and standard) lever mount.

JohnDThompson 

Looks like it's a goner. Assuming the frame has standard lever bosses, any friction lever could be mounted on them. Otherwise, SIS levers do turn up on eBay fairly often.

Vinnems

I went with the 105s since they were only $40 shipped for NOS and the Ebay prices for NOS 600s are insane. Thanks for the help guys. Until they arrive, looks like I'm on a two speed