I've got my '05 XL1200R at least partially uncorked, now with a Zipper's air filter kit and Khromewerks slip ons. It runs pretty well but I can't say that I consider the throttle response anywhere near as good as what I experience on my '01 FXD which has a 42mm flat slide on it.
I can't swear that its the carb that I am feeling here, could just be that the FXD, with its 95" kit and cams just hits harder off idle than the 1200R but I'd be interested in the experience of anyone who has changed carbs on their bike and how they think it changed the response of the bike.

Eheh
You're talking about the main difference between the flat slide carbs and CV carbs.
CV carbs: smooth power delivery, good mileage, very little affected by altitude, poor maintenance.

Flat slide carbs: very impulsive and strong power delivery (expecially if used in 4 cyl bikes), poor mileage, affected by altitude air/fuel mixture vary a lot, needs maintenance at almost twice a year to be always perfect.

And a flat slide can give poor performance if the intake system is flowed and engine tuned for a CV carb.

I think working on a CV carb, tuning it very well you can feel a smooth power delivery and good performance. And last but not least, you'll save lot of bucks.

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Mr. Mechano
Kawasaki ZRX1200 152hp
Soon XL1200C red/sylver

Something is definitely up. I have a nice snappy delivery from the throttle.

Eheh
You're talking about the main difference between the flat slide carbs and CV carbs.
CV carbs: smooth power delivery, good mileage, very little affected by altitude, poor maintenance.

Flat slide carbs: very impulsive and strong power delivery (expecially if used in 4 cyl bikes), poor mileage, affected by altitude air/fuel mixture vary a lot, needs maintenance at almost twice a year to be always perfect.

And a flat slide can give poor performance if the intake system is flowed and engine tuned for a CV carb.

I think working on a CV carb, tuning it very well you can feel a smooth power delivery and good performance. And last but not least, you'll save lot of bucks.

--
Mr. Mechano
Kawasaki ZRX1200 152hp
Soon XL1200C red/sylver

Interesting, I've had that 42mm flat slide on my FXD for 20k miles now and I can't really say I've experienced any of what you describe. It has what I would call extremely good throttle response (hardly impulsive). I've ridden it in elevations from sea level to 11000 feet and it does lose power but no worse than any other bike I've ridden. Mileage has been 40-42 mpg, similar to what many people report for that model. Maintenance has been minimal, just what it gets at the normal service intervals. The money, yeah it did cost a little.
As to my 1200R I'm convinced it runs fine. It responds just like any bike I've ridden with a CV carb. I think I'm used to the flat slide and also my SV 1000 which is injected, both are pretty immediate in throttle response. I wouldn't say one way is better than another, just different. I'm pretty sure at this point I'll leave the 1200R alone, I've spent enough on it anyway for now.

I've run both carbs. There is little to no difference in throttle response between either carb if properly tuned. Actually, if the Mikuni isn't tuned right, throttle response will suffer more than if the CV is out of tune. The vacuum operation of the CV makes for one nice smooth operating carb even under less than ideal conditions. If the Mikuni isn't right, you can whack the throttle and get a big ol' bog.

Interesting, I've had that 42mm flat slide on my FXD for 20k miles now and I can't really say I've experienced any of what you describe. It has what I would call extremely good throttle response (hardly impulsive). I've ridden it in elevations from sea level to 11000 feet and it does lose power but no worse than any other bike I've ridden. Mileage has been 40-42 mpg, similar to what many people report for that model. Maintenance has been minimal, just what it gets at the normal service intervals. The money, yeah it did cost a little.


I've worked on both Mikuni HSR and Keihin FCR batteries of 4x carbs for japs. All of them made the bike really nervous, great power delivery but brutal way.
Difficult to setup due to the many different settings.
On big twins the single flat slide is a bit more smooth due to the character of the engine, slow to rise revs.
I've worked on some evo and metric cruisers and I hadn't good results with the first setup.
I've been obliget to study a lot from some documentations and setup manuals delivered with this units (expecially the racing). And the setup was almost different from bike to bike.
I don't say it's impossible to obtain good results, I say it's difficult. You have been lucky, there's lot of guys out there (both selfmade and poor experience mechanics) are still trying to make them give out the best performances.

And into Internet there's very little literature about them. Cor CV carbs, you can join the smallest mailing list or website, and you'll get tons of infos about a CV. I don't want to think how difficult can be for an Edelbrock or Bendix.

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Mr. Mechano
Kawasaki ZRX1200 152hp
Already bought, will arrive next week: '04 XL1200C