Bicycle Mechanics - SIS SHIFTER/DERAILLEUR Adjustment

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jfz
12-27-02, 03:05 PM
I am working on a bike I found at the dump. It has an SIS SHIFTER/DERAILLEUR and the chain jumps when I have it on the largest rear sprocket to the next one, I believe the shifter may be loose and wanted to know if you just pry the top of the shifter off to get at the adjustment screw?

pokey
12-27-02, 03:50 PM
Originally posted by jfz
I am working on a bike I found at the dump. It has an SIS SHIFTER/DERAILLEUR and the chain jumps when I have it on the largest rear sprocket to the next one, I believe the shifter may be loose and wanted to know if you just pry the top of the shifter off to get at the adjustment screw? I have yet to see an adjustment IN a shimano sis shifter.The adjustment in in the rear derailer,assuming there is nothing else contributing to the problem. Try www.parktool.com for derailer adjustment. The chain and the cassette could also be worn.
mike
12-28-02, 06:13 AM
The SIS is an index shifter. Don't mess with it.

Check the cable tension. Shift the chain onto the smallest sprocket and tighten the cable.

Check your sprockets to make sure you don't have wear or damage.

pokey
12-28-02, 07:14 AM
Originally posted by mike


Check the cable tension. Shift the chain onto the smallest sprocket and tighten the chain.

?????????????:confused: :confused:
D*Alex
12-28-02, 08:33 AM
If the chain is "jumping" off only one cog (or just 2 or 3), chances are that the cogs and chain are worn out. That's probably the reason somebody threw it out.
Hunter
12-28-02, 09:07 AM
This sounds like a limit screw adjustment. If the chain jumps from the bigger rear cog to the next one down back the limit screw out a quater turn.
mike
12-28-02, 11:09 AM
Originally posted by pokey
?????????????:confused: :confused:

Oops, I meant tighten the cable, not the chain. Sorry, too sleepy :(

Anyway, as D*Alex and I suggested, there is a high probability that the sprockets or the chain ring is worn.
WorldIRC
12-28-02, 11:24 AM
I agree, if the derailleur skips on 2 or 3 cogs then its usually worn. If it skipped only 1, then its usually out of wack.
roadbuzz
12-28-02, 09:46 PM
Just in case, take a good look at the derailleur hanger, too, and make sure it isn't bent.
jfz
12-29-02, 12:06 PM
Thanks all for the help! The limit screw was the problem.
mike
12-29-02, 06:49 PM
Originally posted by jfz
Thanks all for the help! The limit screw was the problem.

Oh, GAWD!