Swapping out position-400 derailleur for modern tourney

[iemandvandezaak]

I'd like to get my mothers late 70's Dutch bicycle back on the road here in Amsterdam. It's a 5 speed bike now equipped with a positron 400 derailleur but it's in unknown condition, the shifter cables are shot and the chain is missing.

Some people here mentioned in a very old thread by someone else swapping it out for a (6s) RD-TZ50-GS Link and a cheap thumb/grip shifter.
Since I lack the chain I figured I might as well change the cassette and, if needed, the freehub for something more modern/cheap and go the 6s route.

Is that all feasible and would it all play nice together? Would I also I need a different free hub?

Thanks in advance!


6S Tourney TZ Rear Derraileur - RD-TZ50-GS Specs
Tourney Multiple Freewheel 3x6 speed MF-TZ500-6 Specs (HG/UG compatible)
Shimano CN-HG40 6-speed chain
Shimano Revoshift grip shifter SIS index SL-RV200-6R Specs

 

[midlife]

Is there enough holding the handlebar stem in the steerer?

 

[Sharky]

You seem to be mixing up terminology.
Cassettes and freehubs go together, but screw on freewheels are self contained and don't have a separate freehub.
I would get a new chain, new inner & outer cables. Does the gear lever still work? Is it friction or indexed?
Put the new stuff on and see how it all works.

Good luck - it's a nice project

.... and lower the handlebars as @midlife says above

 

[Cycleops]

Should all work okay. Don’t forget you need a freewheel not a freehub cassette. I’ll bet the existing rear derailleur still works so I should give that a go first to see if it works with the grip shift.

 

[iemandvandezaak]

Is there enough holding the handlebar stem in the steerer?

Seems to be!

You seem to be mixing up terminology.
Cassettes and freehubs go together, but screw on freewheels are self contained and don't have a separate freehub.
I would get a new chain, new inner & outer cables. Does the gear lever still work? Is it friction or indexed?
Put the new stuff on and see how it all works.

Good luck - it's a nice project

.... and lower the handlebars as @midlife says above

Oh right. I believe the current gear lever is a simple friction thumb lever. Cheers.

Should all work okay. Don’t forget you need a freewheel not a freehub cassette. I’ll bet the existing rear derailleur still works so I should give that a go first to see if it works with the grip shift.

It might! To replace the original cable is about as expensive as to buy a new derailleur etc. So I figured I might as well replace the whole thing - since I need it to bring me to uni so reliability trumps looks

 

[SkipdiverJohn]

Is there enough holding the handlebar stem in the steerer?

It looks a bit alarming on the face of it but consider the whole frame. That's a pretty big size for a womens frame going by the seat tube, but it has quite a short head tube as you would typically find on a medium sized frame. The only way to get the bars up to a comfortable upright riding height is to use a very tall stem. I would still take it out to check it though, and ensure that there was at least a good two inches inside the head tube when refitted, just for peace of mind.

 

[Cycleops]

It looks a bit alarming on the face of it but consider the whole frame. That's a pretty big size for a womens frame going by the seat tube, but it has quite a short head tube as you would typically find on a medium sized frame. The only way to get the bars up to a comfortable upright riding height is to use a very tall stem. I would still take it out to check it though, and ensure that there was at least a good two inches inside the head tube when refitted, just for peace of mind.

If you look closely you can see a ring where the stem looks like it was previously so it looks like it has been raised quite a bit.
The other thing that needs to checked are the tyres which look like they might be perished.

 

[Astore]

That handlebar stem looks way too high for safety. If it is a Shimano Positron derailleur, that pre-dates SiS and I'd imagine finding compatible parts would be nigh-on impossible. I would go with a Shimano Tourney GX rear derailleur, 6 speed 14-28 Shimano screw-on freewheel and a Shimano IG51 chain. A 6 speed Shimano or SunRace handlebar shifter and cable should work fine. All of this is available on eBay at comparatively low cost; under £45 for the lot if you keep your eyes open, and you'll have a nice, useable machine at the end of it.

 

[Gunk]

Try one of these, 5 speed and £20

https://www.ebay.co.uk/itm/333505761328