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 Post subject: 13 tooth sprocket?
PostPosted: Sat Dec 30, 2017 1:41 pm 
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Joined: Tue May 17, 2016 10:03 pm
Posts: 134
Location: Burton upon trent
As I'm converting my Rumi from 8 inch wheels to 10 inch I'm wondering where I can get the 13 tooth chain sprocket from. Is there one from another machine that will fit? Any advice appreciated.

Regards

John.


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Wed Jan 10, 2018 8:20 pm 
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Joined: Fri Dec 28, 2012 7:03 pm
Posts: 522
does any one know the number of teeth on junior gentleman gearbox sprocket and chainsize,thanks arthur.


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Thu Jan 11, 2018 6:46 pm 
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Joined: Mon Aug 24, 2009 12:36 pm
Posts: 499
Location: South Wales UK
arthur lewthwaite wrote:
does any one know the number of teeth on junior gentleman gearbox sprocket and chainsize,thanks arthur.


18 tooth sprocket, 1/2"x3/16 renold 110044 chain.

Ian


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Sat Jan 13, 2018 5:19 pm 
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Joined: Fri Dec 28, 2012 7:03 pm
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Cheers Ian. My mate Malcolm bought a Junior and his one has 16 teeth. Does it depend on rear sprocket teeth size as different sprockets used for racing. Graham bought a Junior Gentleman without a frame. Perhaps he could check his front and rear sprocket sizes. I will try a few other people to see if a list of sizes can be kept for the record. I am going to count my rear wheel sprocket to see what it is.


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Tue Jan 16, 2018 6:09 pm 
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Joined: Mon May 02, 2011 11:44 pm
Posts: 74
arthur lewthwaite wrote:
does any one know the number of teeth on junior gentleman gearbox sprocket and chainsize,thanks arthur.



My Junior Gentleman is running an 18-tooth front sprocket and a 47-tooth rear sprocket. I have no reason to believe that this setup has ever been changed since it was sold new.


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Tue Jan 16, 2018 6:15 pm 
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Joined: Tue May 17, 2016 10:03 pm
Posts: 134
Location: Burton upon trent
As long as the number of teeth on the front and rear sprockets multipied together is approx the same it doesn't matter. If you have a 16 tooth front sprocket you need a 53 tooth rear.
18x47= 846 and 16x53 =848


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Tue Jan 16, 2018 6:16 pm 
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Joined: Tue May 17, 2016 10:03 pm
Posts: 134
Location: Burton upon trent
That's assuming the wheel dia is the same of course.


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Tue Jan 16, 2018 6:28 pm 
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Joined: Tue May 17, 2016 10:03 pm
Posts: 134
Location: Burton upon trent
I think I'm talking rubbish. You need to divide the front sprocket by the rear. 18 divided by 47= 0.3829. So 16 divided by 0.3829 gives you 42 teeth on the rear sprocket to keep the same gearing. Sorry.


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Mon Jan 22, 2018 5:35 pm 
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Joined: Mon Aug 24, 2009 12:36 pm
Posts: 499
Location: South Wales UK
arthur lewthwaite wrote:
Cheers Ian. My mate Malcolm bought a Junior and his one has 16 teeth. Does it depend on rear sprocket teeth size as different sprockets used for racing. Graham bought a Junior Gentleman without a frame. Perhaps he could check his front and rear sprocket sizes. I will try a few other people to see if a list of sizes can be kept for the record. I am going to count my rear wheel sprocket to see what it is.


Hi Arthur. I've done further checking of my aging ex Gentlemen (fast riders). They concur, over the counter they all came with 18 x 47, but performed much better on a 17 x 47 combination. Looking at personal records, the rear sprockets that my first racer arrived with, were 47, 48, 49 and 50.

Ian


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Fri Feb 09, 2018 2:01 pm 
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Joined: Thu Jun 11, 2009 10:05 am
Posts: 3276
Location: Amsterdam
Hi John,

There is one seller in Italy offering Moto Rumi front sprockets in different sizes.

You can find it at the next link: https://www.subito.it/accessori-moto/ru ... 956184.htm

Attachment:
Moto-Rumi-front-sprokets.jpg


Good luck!!!
Hugo


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 Post subject: Re: 13 tooth sprocket?
PostPosted: Fri Feb 09, 2018 2:15 pm 
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Joined: Tue May 17, 2016 10:03 pm
Posts: 134
Location: Burton upon trent
Thanks Hugo, but one of the forum members in Argentina has got me one from a vendor over there and is posting it to me. So, hopefully it will arrive fairly soon.

Regards

John.


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