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B 50 gearing #773451
05/12/19 11:30 am
05/12/19 11:30 am
Joined: Jan 2006
Posts: 2,072
Asheville, NC
Mike Baker Offline OP
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Mike Baker  Offline OP
BritBike Forum member

Joined: Jan 2006
Posts: 2,072
Asheville, NC
Got my first BSA off the lift and out for a quick ride yesterday. It's a B50MX, came to me with 19/55 gearing. I replaced the 55 with a 46 as it is a roadrace bike. First impression is it seems geared tall. Almost feels like I'm leaving in 2nd gear. Are there different gearboxes for MX versions vs. roadgoing b50's? Or should I be looking for a 50t rear sprocket?
Thanks from the BSA virgin

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Re: B 50 gearing [Re: Mike Baker] #773469
05/12/19 3:52 pm
05/12/19 3:52 pm
Joined: May 2002
Posts: 697
Winston-Salem N.C.
D
D.W.R. Offline
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D.W.R.  Offline
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D

Joined: May 2002
Posts: 697
Winston-Salem N.C.
Yes, the MX box has a slightly taller first gear making the ratios a bit closer, everything else is the same.
Don R.


71 Rocket 3
72 B50 MX
66-71 A 65 Bitsa
96 Trident 900
Re: B 50 gearing [Re: Mike Baker] #773470
05/12/19 3:54 pm
05/12/19 3:54 pm
Joined: May 2002
Posts: 697
Winston-Salem N.C.
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D.W.R. Offline
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D.W.R.  Offline
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D

Joined: May 2002
Posts: 697
Winston-Salem N.C.
I would think a 50 tooth rear might be a better fit with the 19.


71 Rocket 3
72 B50 MX
66-71 A 65 Bitsa
96 Trident 900
Re: B 50 gearing [Re: Mike Baker] #773482
05/12/19 5:13 pm
05/12/19 5:13 pm
Joined: May 2013
Posts: 5,560
West Yorkshire
Allan Gill Online happy

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Allan Gill  Online Happy

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Joined: May 2013
Posts: 5,560
West Yorkshire
You might consider a standard box for it, even geared tall they seem to have a lot of grunt and still feel undergeard most the time


beerchug
Re: B 50 gearing [Re: Mike Baker] #773496
05/12/19 7:11 pm
05/12/19 7:11 pm
Joined: Sep 2004
Posts: 1,020
Farnham, Surrey, UK
gunner Online content
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gunner  Online Content
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Joined: Sep 2004
Posts: 1,020
Farnham, Surrey, UK
According to the Rupert Ratio manual, the B50MX used a 14 tooth gearbox sprocket with 52 teeth on the rear wheel, the B50SS used a 16/52 combination. Your setup sounds tall so maybe try 50 or 52 on the rear wheel.


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: B 50 gearing [Re: Mike Baker] #773500
05/12/19 8:30 pm
05/12/19 8:30 pm
Joined: Dec 2004
Posts: 9,963
Scotland
kommando Online content
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kommando  Online Content
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Joined: Dec 2004
Posts: 9,963
Scotland
I run a B44 with MX cam 19/49 sprockets and get relaxed cruising.

Re: B 50 gearing [Re: Mike Baker] #773553
05/13/19 10:37 am
05/13/19 10:37 am
Joined: Jan 2006
Posts: 2,072
Asheville, NC
Mike Baker Offline OP
BritBike Forum member
Mike Baker  Offline OP
BritBike Forum member

Joined: Jan 2006
Posts: 2,072
Asheville, NC
Thanks for the replies, all. I think I like the idea of the MX gearbox. We'll see what happens on the track. A 50 or 52 rear is a necessity though. I'd hate to toast the clutch at the start of a race. It's all a compromise, though. NJ is one of those tracks with a long front straight. Rob H told me that he ran 21/50 almost everywhere but I think he was about 600cc with some other goodies.


Moderated by  Allan Gill, Jon W. Whitley 

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