currently running a nice spec pinto with vulcan max flow 3 head fr33 cam, lightened balanced etc,

would i see much improvement from changing to weber 45`s from my current 40`s which are currently on a 34 choke.

anyone under taken such a change, ?

Properly set up 40's are more than adequate for anything up to 200bhp, doubt you'll see any gains whatsoever fitting 45's

You could potentially gain a bit of top end power - but possibly lose a bit of low to mid range tractibility.

Actually it is the choke sizes which really make the difference, you could just put larger chokes in your 40's for a moderate increase.

I think if I was doing it I would go for bike carbs rather than 45's - you should get a better overall performance mid range and top end and better running, idling etc.

Cheers

Mark

RECOMMEND ANY BIKE CARBS?

Yamaha R1, ZX9R, Fireblade / Blackbird

R1's seem to be a popular choice. Talk to Steve Bogg at Bo Bros he'll point you in the right direction.

http://www.boggbros.co.uk/contact.html

these are still carbs right ? not injection.. so why are they so much better than car carbs?

They are called constant velocity carbs and have a jet with a needle attached to a vacuum slide like old SU carbs but done by the Japanese they work very smoothly and accurately over the entire rev range. As good as 45's at the top end but better low to mid range, better economy and no fiddling all the time like you get with 45's.