heres an indication from wolf creek racing on the maxxed out weber and mikunis they do and you can see a step for the chokes which impedes on flow unlike bike carbs

http://www.wolfcreekracing.com/images ... refurbed_u20/roadnew3.jpg

http://www.wolfcreekracing.com/index. ... yout=blog&id=33&Itemid=23

how much difference would there be in flow comparing twin 45's and a set of r1 carbs

r1 carbs having no chokes and 45 with chokes would it mean the r1 could have the potential to flow similar to 45's?

The yamaha R1 motorbike used mikuni carburetors, which have choke (venturi) - they are variable venturi.

When the carburetor flows more air than the engine can possibly draw, going to a larger carburetor will not increase the HP. That is why single SU can make as much HP as multiple carburetors

Just to be sure I'll bring it up:

R1 carbs being CV type have butterflies in them whereas FCR carbs and others have slides only. The big flow advantage of FCR is that once the slide opens there is nothing in the way i.e. throttle shaft etc.

Motorcycle carbs tend to be a little bit better even CV style, not that DCOE carbs are bad just the bike carbs of the same size seem to flow more.

Tom

very good point by RT, the CVs seem to work better for midrange and daily driving when tuned well while most flat slides are usually for higher end angry hp activity.
Even most road bikes still favor the butterfly over the flat slide setup mainly because all or nothing power is not safe on a 2 wheeler.

I agree. the simpler setup of a supercharger or turbo with an adequate single carburetor feeding fuel through it is optimal.

I bought a set of fz1 bike carburetors for $125. You can probably do equally with some looking around. Bigger is not always better as the engine only needs a modest amount of air at the speeds it normally operates.

I've fitted R1 fuel injection throttle bodies to my A15. They are well oversized but FI is a bit more forgiving, just means the low end throttle response will be a bit more intense (not tuned or plumbed up yet but getting there). From memory they're around 45mm ID and the rubber mounts taper down to line up quite nicely with 1-1/2" exhaust pipe (OD, wall thickness is 1.6mm).

If you're not into fuel injction/ ECU etc. and only mild boost I'd support most of the other comments that say go for a single carb, draw through setup. Bolt it all onto the standard manifolds. The more stuff you change the longer it'll take to get it going and the more problems you'll come across.

What ever you do, have fun with it!

Im going fzr carbs on my l18 eventually. 38mm throats straight through should flow better for my use than su style 40mm r1 carbs.

Just need manifold to be done.

Another thing to note - maybe not mentioned before is when going NA with quad carbs, bike carbs have one another advantage of a more direct flow path than webers designs when used on an A series. If you look at webers, solex-mikunis & dells, they can be made to work amazing with an A yet there is definitely more bends unlike some compact bike carbs.
Bike carbs seem to be easier for different choices of air filters, lengths and angled designs as well as cheaper, lighter and need less room in our small bays.
Heres a nice r1 setup not tuned yet
http://www.youtube.com/watch?v=Hy9xZZtg5Aw

heres a nice 1200 36hp beetle that doubled its hp with simple supercharged setup single carb look as his many vids where he tries different single carb design and layouts.
http://www.youtube.com/watch?v=-1WPxAKgNlM
http://www.youtube.com/watch?v=eUuDKGd1mVE
http://www.youtube.com/watch?v=YBwkugoBPq4
http://www.youtube.com/watch?v=hg7umXODtjE