Shimano 600 derailleur issue

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Shimano 600 derailleur issue

Postby Tomca74 » Tue Oct 15, 2013 7:00 am

I have been riding this old bike a couple of times a week since tidying it up but sometimes the rear derailleur won't shift to the small cog. I'm unsure what problem to be looking for, cable/spring/other bits.

Any help to narrow down the problem will be much appreciated.

Image

And it has bar end shifters (if that makes any difference)

Image
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by BNA » Tue Oct 15, 2013 1:16 pm

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Re: Shimano 600 derailleur issue

Postby Duck! » Tue Oct 15, 2013 1:16 pm

Disconnect the cable from the derailleur and manually push the derailleur through the gears, then let it drop back out. If the chain still hesitates to drop to the smallest sprocket with no cable influence, then wind the "H" limit screw out gradually until the chain drops smoothly onto the gear. Reconnect the gear cable and tune as normal. If it continues to shift roughly, then look at the cable itself. If it's rough & gungy, replace it and the outer casing.
I had a thought, but it got run over as it crossed my mind.
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Re: Shimano 600 derailleur issue

Postby HappyHumber » Tue Oct 15, 2013 1:45 pm

+1 to Ducks comments. Good cursory, first step advice.

Lettuce know how you go from there.

Looks like a good, solid old machine you got there from the teaser pics. Don't ever let any numpty at a bike store tell you can't get 'part X' or 'part Y' for those any more
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Re: Shimano 600 derailleur issue

Postby Tomca74 » Tue Oct 15, 2013 2:49 pm

Yep just done all that. What i observed was the spring tension is non existent at the last cog and the chain wants to jump back up a gear when you let go of it. Will using the cable to exert force to hold it there be harmful or should I be fixing the spring? The cable is smooth and moves freely through its casing.

Happy humber unfortunately most shops turn their nose up at it but this forum has been a great resource. I was lucky enough to be contacted by a member with nos brake hoods for the bike and hope one day to be able to contribute instead of just seeking advice.
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Re: Shimano 600 derailleur issue

Postby HappyHumber » Tue Oct 15, 2013 3:40 pm

Maybe the hanger is out of alignment?

As the top gear (smallest cog) should be the 'default' position at the back, you shouldn't expect to be much, if any, tension on the spring. Changing down is pulling on the spring, whilst changing up is the controlled relase of the tension.

That said, I have heard of old springs getting worn out. Haven't encountered it myself as yet. This might be symptomatic of the problem. After eliminating everything else, I would fish around here on the WTT/WTB and I'm sure someone will have a similar or equivalent old RD in their parts bins. Might be easier than finding and replacing just the spring.
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Re: Shimano 600 derailleur issue

Postby elantra » Wed Oct 16, 2013 5:55 pm

Tomca74 wrote:Yep just done all that. What i observed was the spring tension is non existent at the last cog and the chain wants to jump back up a gear when you let go of it. Will using the cable to exert force to hold it there be harmful or should I be fixing the spring? The cable is smooth and moves freely through its casing.

Happy humber unfortunately most shops turn their nose up at it but this forum has been a great resource. I was lucky enough to be contacted by a member with nos brake hoods for the bike and hope one day to be able to contribute instead of just seeking advice.


Nice bike, what is it ? Malvern Star ???

If you can't get this problem sorted send me a PM.
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Re: Shimano 600 derailleur issue

Postby Tomca74 » Wed Oct 16, 2013 7:34 pm

Hi Elantra it is a Speedwell Olympic.
Image
I pulled the wheel off my other bike and in comparison, the spring has lost all tension by the time it gets to the small cog. Being old, I think it may need a new part (if possible) otherwise a cursory look on ebay I may find a gen 1 unit for ~$200.
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Re: Shimano 600 derailleur issue

Postby elantra » Wed Oct 16, 2013 9:27 pm

Tomca74 wrote:I pulled the wheel off my other bike and in comparison, the spring has lost all tension by the time it gets to the small cog. Being old, I think it may need a new part (if possible) otherwise a cursory look on ebay I may find a gen 1 unit for ~$200.


If only you had have known about the recent brisbane (Coorparoo) swap meet which was on the same day as the Bathurst car race.

There was a gent there with about three Shimano 600 rear derailleurs for sale, i think the asking price was about 20 dollars. :wink:
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