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#402565 - 11/07/11 10:59 pm Convert a Dual Carb to Single Carb???
Paula C. Buls Offline
BritBike Forum member

Registered: 02/14/10
Posts: 3
Loc: Texas
This is my first post in quite some time. I have had a '69 Lightning that I purchased as a bitsa bike a few years ago and kept running as a daily rider until I went back to grad school and had to put it aside for awhile.

Now, I'm done with school and wanting to put the bike into good running order. I've decided to tear into it and do some significant redo as part of getting it in top shape. One of the things that I had always been concerned with when I had the bike running previously was that it had an incorrect tank on it (I believe the tank on it was actually a rocket 3 tank) I now have a correct tank for it and am collecting other needed parts. It had been missing the engine steady stay and while I had the tank off discovered the reason for its missing. The mounting tab on the head is broken off. I don't know if this is something that can be repaired or if I should start scouting for a good used replacement head to rebuild. (I am planning on tearing down the engine to redo the bottom end and clean the sludge trap and make sure evrything is in reasonable condition)That of course leads to the question of whether I am better off converting to a single carb head and doing away with some of the headaches of having the dual carbs. The existing carbs are not in great shape and at the least will need to be resleeved. I am not interested in achieving maximum speed out of this bike and am more interested in fuel economy and reliability. At the risk of starting a huge debate I was wondering about the pros and cons of converting a lightning to a thunderbolt.

Any thoughts?

Thanks in Advance,

Paula
_________________________
1969 BSA Lightning "Penelope"
1978 BMW R80/7 "Freyja"

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#402586 - 11/08/11 12:49 am Re: Convert a Dual Carb to Single Carb??? [Re: Paula C. Buls]
BONZO R.I.P Offline
BritBike Forum member

Registered: 08/08/01
Posts: 3348
Loc: Michigan, USA
if you are not looking for performance or correctness and you are looking for a more troublefree ride then you are on the right track.The only downside I can see is the sidecovers for the twin carb head might leave a bit of a gap . I rode mine like that for several seasons and really enjoyed it .I'd definitely recomend the stock 928 carb .the bike will have a different personality but it sounds like what you are after .

FWIW-BONZO

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#402587 - 11/08/11 12:50 am Re: Convert a Dual Carb to Single Carb??? [Re: Paula C. Buls]
Lannis Online   content
Life member

Registered: 07/28/01
Posts: 8253
Loc: Old Pop in an Oak
I've often thought about it; seems like I always have A65s with dual-carb heads even though I'd be just as happy with a single carb.

I've got a single-carb head sitting on the shelf, and it would be easy to rejet one of my carb bodies for it, and just use it on the Firebird. No more having to sync carbs, and do everything twice, etc.

But I've never gone to the trouble. To be honest, a properly sorted set of Amals with sleeves will last a long time (been 30,000+ miles so far and still starting and idling easy). And I guess I do sort of like that little bit of top-end "kick" that you get on a dual-carb bike; and two carbs aren't really that much trouble.

But if you need a new head anyhow, and have to source one, NOW would certainly be the time to convert. Just make sure you get the right size carb and jet it right.

It should be fun "getting back into" the old bikes!

Lannis
_________________________
"What's the plan?"

"Plan? There ain't no plan!"

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#402588 - 11/08/11 1:06 am Re: Convert a Dual Carb to Single Carb??? [Re: Lannis]
raf940 Offline
BritBike Forum member

Registered: 03/02/06
Posts: 3329
Loc: gastonia nc
hi..i have a 1968 A65 bitsa...it has lightning frame and engine but the box of bits had a single carb head ..i put an AMAL 928 on it and i really love it...not as fast as my T120 but really tractable and easy to tune....


Edited by raf940 (11/08/11 1:07 am)
_________________________
1972 Triumph T120
1968 BSA A65
1968 MGB Roadster
1979 Chevrolet Camaro Berlinetta
1969 Honda Mini Trail
2004 Honda Shadow Aero
1972 BSA Thunderbolt
1975 yamaha xs650b
1974 Norton Commando (calvin's other bike that lives here)

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#402609 - 11/08/11 2:41 am Re: Convert a Dual Carb to Single Carb??? [Re: Paula C. Buls]
Bob~NJ Offline
BritBike Forum member

Registered: 12/21/05
Posts: 447
Loc: Camden NJ USA
Hi Paula,

Would really like to see a pic of the broken head steady tab on your engine. Never seen one before. Anything can be repaired......

Cheers~Bob
_________________________
A65LB

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#402677 - 11/08/11 1:54 pm Re: Convert a Dual Carb to Single Carb??? [Re: Bob~NJ]
Paula C. Buls Offline
BritBike Forum member

Registered: 02/14/10
Posts: 3
Loc: Texas
Here's the pic.



I'm open to repairing if that's a reasonable option. I'm dubious about buying a used head and then still having to sort that one out.

Cheers,

Paula
_________________________
1969 BSA Lightning "Penelope"
1978 BMW R80/7 "Freyja"

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