Twin Carb envy!

[alanp]

I parked my RGS rep A10 next to a Gold Star and a twin carb '59 Bonneville the other day and have to admit that the other engines looked much better with the carbs in clear sight than mine. I know twin carbs can be a nightmare to set and keep set but....if only mine had twin carbs.
I know that occasionally you see twin carb A10 heads on sale but very very rarely and big money is involved.
Has anyone any knowledge of the possibility of converting the A10 head to twin carbs?
Thanks
Alan
PS I know there is another topic on twin carb heads going but I'm interested in modifying a standard head.

[bsa-bill]

Can't give names (don't know them) but there are guys who convert heads to twin carb, maybe some one else has more info

[Goldy]

I cannot see the point in doing that other than giving the ethanol two carbs to attack instead of one.

[bsa-bill]

I cannot see the point in doing that

10% zing 90% bling

But if blings your thing - way to go

[trevinoz]

It's a big job, Alan.
                               I have seen a few but it involves cutting off the manifold, fabricating new stubs and having them welded on.        
                         Trev.

I haven't actually seen one mounted on a bike yet so I can't offer any opinion on performance.

[Taffy]

eBay 200587583731 about as good as they go.Most if these are stateside.I've seen them on A10s but they are for looks more than anything.Yes extreme track use with tt gp carb may be usefull!!

[A10Boy]

I remember reading somewhere that when Triumph converted the T110 to twin carbs to make the Bonny, BSA tested twin carbs on the A10 and found that it made no detectable difference upto about 99% of full speed and added only a few MPH at the top. My view is that when twin carbs were fitted to the A65's it was more of a fashion thing to sell higher numbers in America. Most of the power gained on the hotter models was from better breathing, higher compression and more sporty camshafts.

Call me old fashioned, but I think a well set up single carb is better than twin carbs unless you are going racing.

[Jim]

I've got an early dual port alloy A7 head which has a detachable manifold, if you remove the manifold you can convert the head to dual carb and it should fit on an A10. This is what I hope to do at some stage, putting 30mm MkII concentics on it. There would appear to be a fair amount of work needed in porting the head. I have few illusions about any performance gain but I agree with alanp about the aesthetics.

[Jim]

Just found a rather poor photo of the head with a 30mm manifold attached to show how much metal needs removing. Hopefully it has uploaded.

[JulianM]

Hi Alan,

I personally think the twin carb head is a great idea and great option,
Without quoting hearsay and to be honest rather unsubstantiated musings I think it is the way to go for several reasons,

1. On the flow bench, even an un ported and un modified twin carb head out flows a fully ported GS big valve head by a very large margin.
2. If you are running a modified performance type engine you will need better flow than a single carb head can easily give you.  Just think about it,  a very good GS single carb engine gives about 48bhp top whack!  Not great for a 650 is it!
(A cooking Bonneville engine puts out the same power as a good modified GS,  Just ask yourself Why?)
3. Why on earth do people keep saying twin carbs are impossible to setup correctly?  I have many twin carb bikes and not one of them "falls out of tune"    I think most people who complain about one side running cold etc are actually overlooking the idiosyncrasies of the single point magneto rather than carburettor tune.  Why would a carb "suddenly jump out of tune?   I have never known it!  If this were the case then you would see the roads littered with dozens of 4 cyl bikes after all their carbs went out of sync and made them stop, imagine setting up 4 carbs if 2 are impossible!!    What do they say about bad workmen?  Blaming tools?  or carbs?
4. OK around town and slow running a single carb will surely work at least as good if not slightly better than twin carbs, but who builds a performance engine to go shopping?
5. In the car world we laugh at Porsche Cayman owners when they tell you "why they didn't want a 911"   actually because they couldn't afford a 911 but they won't tell you so.  I think a little like people without twin carbs telling you why they don't work and why one carb is best!   Go to the race track and see if you can find anyone with a twin running a single carb if they have an option.
6. They look great!
7. Because you can and it all boils down to personal taste and personal preference!

Julian.
(Hope I don't upset anyone, not meant to)

[The pirate]

If I wanted to go fast I would have kept my HONDA fireblade - but i am still looking for a twin carb head for my A10 SR - its the look that cant be beat. Best of luck finding/making a twin carb head.

[JulianM]

"If I wanted to go fast I would have kept my HONDA fireblade"

Yes but the old BSA "Feels" faster 
Sheesh, when you do the ton on an A10 you really know you are doing it!  on a Fireblade you are just out for a little jog!


Julian 

[metalflake11]

Different strokes for different folks! ....... I understand why people like twin carbs, but it's not for me. One carb leads to a simpler life carburation wise normally, and is 50% cheaper when you replace worn out ones.
Mine can take off faster than my brain works, and will go a lot faster than my ageing body would like to fall off at. So I'll leave the twin carb business to other, braver riders.

[bikerboy]

Just thought I would show you my setup, this is a 70mm Super Rocket cylinder head and the carb spacers are from a T120/T140. The threads are helicoiled as the inner ones need allen bolts because there is no way you would get a spanner in between them. Fortunately the carb spacers already have pipes for a rubber balance pipe to run between them

[bikerboy]

Damn that pic never attached