Carb swap

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Looper
Posts: 98
Joined: Fri Mar 20, 2009 11:04 am
Location: Ireland

Carb swap

Unread post by Looper » Fri Mar 07, 2014 11:50 am

Anyone know a simple carb conversion for early BSA B31s? My amal 276 is knackered and they're pricey, is there a cheaper carb that will fit?

Crankcase
Posts: 432
Joined: Fri May 08, 2009 11:03 am

Re: Carb swap

Unread post by Crankcase » Sat Mar 08, 2014 2:15 am

Asked a fellow B31 owner I know and he reckons not guess you may just have to bite the bullet and buy on . What do you reckon is pricey they seem reasonable to me
A bike on the road is worth two in the garage.

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mervin
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Joined: Mon Apr 27, 2009 1:06 pm
Location: the dark side of dartmoor

Re: Carb swap

Unread post by mervin » Sat Mar 08, 2014 10:19 am

Possibly a mikuni , try http://www.allensperformance.co.uk/" onclick="window.open(this.href);return false;
classic japbikefest 2 http://www.vjmc.com/japbikefest/

Triton Thrasher
Posts: 774
Joined: Wed Feb 18, 2009 12:51 pm

Re: Carb swap

Unread post by Triton Thrasher » Sat Mar 08, 2014 5:32 pm

The cheap option is an Amal Concentric Mark1. An Amal Monobloc will look better, but is dearer. New pre-Monobloc Amals are available too, but dearer again.

http://www.hitchcocksmotorcycles.com/amal/carburettors

Amal will have a specification for your bike, although it will need a little bit of tuning once it's on.

A Mikuni on an old BSA will look silly and will probably be impossible to make work properly.

Looper
Posts: 98
Joined: Fri Mar 20, 2009 11:04 am
Location: Ireland

Re: Carb swap

Unread post by Looper » Sat Mar 08, 2014 6:32 pm

A replacement 276 seems to cost about the same as it's name £276, I was thinking that at about £100 the mark1 would be be a lot cheaper but it looks to me that it would need some kind of extension to the inlet to get it to clear the dyno and oil tank which wouldn't be the easiest of things to make. All in all it might be better to stick with the 276 but 2 1/2 times the price is hard to take if there was a simple way to make a mark1 fit. Thanks for the input.

Triton Thrasher
Posts: 774
Joined: Wed Feb 18, 2009 12:51 pm

Re: Carb swap

Unread post by Triton Thrasher » Sun Mar 09, 2014 12:50 pm

A Mark 1 is a very small carb. Are you sure there's no room?


This B31 has one fitted, but the pic's a bit small to make out how they've done it.
http://www.picstopin.com/400/1953-bsa-b ... a-b31*jpg/


Better pic, worser bike!

http://farm4.staticflickr.com/3562/3383 ... 3d25_o.jpg

Looper
Posts: 98
Joined: Fri Mar 20, 2009 11:04 am
Location: Ireland

Re: Carb swap

Unread post by Looper » Sun Mar 09, 2014 3:16 pm

Maybe it will fit so! I've a mate who's bike has a mark1, I'll take it while he's not looking and try it. Would be great if it does. That second photo.......I've seen a few B31 customs and they always seem to look worse that the original. Thanks.

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