Oiler used the stock (350 I think) VM26 carbs on his 421 originally, not sure what's on his now, probably 34s. Wicked did a build on the RZRD forum where he did dynos of VM26s on a 421 and it made power in the 70s and said it rode well. Bigger carbs = more power and more fuel use of course.
I agree, the mid range is where more cc's help - 'no substitute for cubes' etc. Even without PVs the Athena cyls make reasonable low down power, they are not at all gutless like old non PVs 2T can be. Sure they might feel slower down low as they have more up top (in the same way the VW 1.8 GTi 16v engine felt compared to an 1.8 8v in the 80s - the 16v was more powerful everywhere but it didnt feel like it cos it had more up top and a step in power and that was addictive so everyone focused on that LOL - Drive the brace of Mk2 or MK3s Golf GTIs back to back, the valver is the one you'd buy but youd moan it was gutlees low down, even tho its not, anyway... before i start moaning about the excess weight of the MK3 VR6 version's motor's effect on handling lets get back to bikes...) and there is a step up when you hit the powerband but as the port tune is minimal (almost detuned as standard so you can make them what you want I guess - bear in mind these are banshee units designed to allow you to do what you need; so drag racing on sand or riding with your mates on mud, or just riding with the kids or perhaps dragging on the street for pinks in B'more can all be done with a differen port job) the bike isnt quite as scary as you might expect it to be at the transition, tho it will stretch your arms if you keep it pinned when you are on it. One thing that is interesting, and Im not sure why, is that the UK guys report that the Athena 421s are very fast to rev up in the rev range, one dyno reported it was the fastest revving up 2T they ever had, something in the make up (nikasil is the key perhaps) means they spool up very fast once you open the throttle wide.
Personally, I dont think the 421 is scary. Sure it has power and you can feel it wants to go, but the rider is the boss of it. Arron's 443 that is ported will be... I reckon that will be an interesting ride on standard wheels/tyres and brakes, but I know he knows what he's doing with his build, so I hope he lets me have a ride when he's done. Tho I dont think many 400+cc owners loan their bikes out, too much time/love/money invested etc. I know Im not keen to let someone else ride mine.
(for those interested, Arron's build thread:
http://www.rzrd500.com/phpBB3/viewtopic.php?f=5&t=7765 )
Agree, it all depends on the rider and what you want from a bike, I mean if we were all sensible we would ride CBR600s LOL Anyway, that's why I wrote it in the article on my site, hoping that people choose what they want based on what they need, rather than chasing a bhp or cc target.