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I just got a MTB bike thats been sitting in a garage for a couple of months.

I tried the bike and found out that the rear derailleur(Shimano) wont shift after the 3rd cog . It shifts up to the 3rd cog just fine but after that the shifter wont click and i cant get it to move any low.

Tried playing around with the limit screws and the barrel adjuster but no luck.just want to know what might be causing the problem and solutions.

Thanks

  • 1) Bad adjustment (more likely the barrel adjuster than the limits, but it's easy to look and see if you are hitting a limit). 2) Fouled shifter. May just need a shot of lube -- hard to say. 3) Sticky cable. Usually a sticky cable won't move at all, but sometimes you can get limited motion. 4) Bent derailer or derailer hanger. So basically you just have to look at everything and figure out what's not working. It's not rocket science -- everything (except the innards of the shifter) is there to see. – Daniel R Hicks Apr 10 '17 at 11:50
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From your description it's likely that the pawl responsible for upshifting is seized and not engaging properly. The reason it would be able to shift the first two gears is because for the 1-2 shift the pawl face engages with an edge of the ratchet wheel instead of a tooth and since the trigger moves far enough that you can shift over two gears at once the 2-3 shift is possible using the same mechanism.

To fix this you would need to remove the cover and clean out the old grease using a solvent or degreaser, or even something like PB Blaster or WD40. You'll probably need to move the pawl back and forth to work the old grease out from around the shaft the pawl rotates on. Once the pawl is moving freely (ie, it snaps back against the teeth without hesitation) apply some fresh grease and put the cover back on.

This video describes the problem and fix, at about 1:08 you get a clearer shot of the upshift pawl and ratchet wheel. Most shimano rapidfire plus shifters use a variation of this design, even if you have a different model than depicted in the video you should still be able to clean and regrease the mechanism the same way.

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  • That's plausible if the shifter isn't clicking, but when this happened on one of my bikes it didn't shift reliably at all. And was much worse in the cold. – Chris H Apr 11 '17 at 17:58

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