Rs38 flat sides vs standard 1200 mk1 carbs

[Alex]

Hi. Does anyone know the advantages and disadvantages of rs38 flatsides for road use over standard. I will be putting on a skimed/ported/Kent reground cams head I have a 4-2-1 acrapovic / 5deg advanced ignition. These rs38's seem a lot of money but are they really worth it for road use? 

[Gixer1460]

Unless you are chasing every last HP then no they are wasted! RS36's will be nicer to use on the road!

[wraith]

+1 on that 

Or if you want a bit more out of your carbs and not spend a lot of money get a set of gsxr750 38mm carbs and rubbers with some K&N pod filters get them jetted, you will see a difference.

[Foz]

Just swapped from rs38’s To 36mm cv’s and modded airbox on my 1216 bandit and i’m Really enjoying the smoothness of the cv’s . As a road engine the cv’s are nicer to use but I do miss certain elements of the flatties , namely to accelerator pump delivery. Someone has suggested 38mm cv’s as they have a similar set up 

[dupersunc]

pooftas the lot of you.get some fcr41s on there.

[nlovien]

ref: carb size - had this discussion with racers / tuners - new school and old school and i'm dam't if I can nail down an agreed consensus of opinion based on result - summary is - especially as you've gone to effort of porting and cams - you'll likely be chasing rpm = new school response - go as big as you dare ( use your inlet port entry size as a guide )

old school will tell you go the opposite = as small as you only need to go, it will be more efficient at part throttle, easier to tune ( or read as more forgiving if they are not right on tune ) - ok so no answer for you  my own experience ( was old school) is modern flatslide smoothbores are mucho better at partial fueling these days - i.e. go big

CV versus directlift smooth bore - if its performance then 100% the smoothbore pumper - maybe not if you only look at the top HP but the initial punch / drive / throttle response - no competition ( and you can gain on mpg as an added bonus )

if its good performance with a smoother lazier pick up, lighter throttle etc.. i.e. the stuff that makes mile crunching on the road more pleasant = go CV

[Captain Chaos]

3 hours ago, dupersunc said:

pooftas the lot of you.get a draw through turbo on there.

Fixed

[coombehouse]

Throttle bodies for me. Light throttle & easy to tune.

Previously the motor felt better on 34mm Amals than rs38s