mk2davis

Take some pics. Maybe if we see whats going we can offer some insight.

A smaller rear sprocket will give you less acceleration, not more. Same thing with going bigger in the front. If you do them both, you will have very slow acceleration on the freeway.

That is going to be a tough putt. Gearing that drops rpm on the freeway is also going to lessen perceived power. More perceived power will result in higher RPMs, noise, vibration, etc. Depending on how much slabbin she does, a bigger bike maybe a more realistic option.

OP - I sympathize and wish I could be more helpfu but I'm carbed. I got 99 problems but this aint one. Speaking of alternate programmable ECU's and the like - and I only mention this after the influence of a few adult beverages - what about a Mega/Micro Squirt conversion? This would of course be only if everything else fails. If my brother can convert his '34 V-8 Ford Flathead, I'm sure it wouldn't be too difficult to convert an already FI bike.

I believe the 3g are 36mm, and sizes are generally taken from the venturi. From what I've read, the 4g transitioned to a smaller flat slide carb because the incoming air flows faster at a lower rpm, helping midrange response. You may want to look at http://www.sudco.com/CatalogJPG/014.jpg . It stipulates a 35-39mm carb for a 750. They also list some sample kits they have; instead of getting 4 singles, it may be easier to buy one fourset from a ZX-7R (or similar) and break the rack. Another idea maybe to call them and see if theyhave something from a parallel twin 400cc. I figure any headstart could be useful.

I know my FZR with CV carbs did not respond well to pod filters, but everyone said it had more to do with the length of runners into the carbs being to short especially in the lower RPMs. It felt like there was a hole around 6k. My experience did not seem to be unique. The only bike I had with a flatslide (and a Mikuni at that) was an NSR 50. It wore a Uni filter. I didn't notice any issues at lower rpms, but I basically only rode that bike at WOT. I hit 62 and change on that bike naked (the bike, not me thank goodness).

I always use www.sudco.com , I would think they can get you a single Keihin FCR39 no problem

Just spit ballin here, but I think flat sides are supposed to flow faster with the same size. I vaguely recall something about the different venturis created by the shape of the slide. This also would effect the power curve. And this would also assume your cam timing is setup to deal with the air, but I think we are ignoring this part based on your stipulations. I don't know of a single Keihin that would work on VFR, maybe something for a HD? You'd have to make a custom manifold, but that is not terribly hard. I don't know what if any the advantages would be of the single carb set up. It would make jetting for elevation change easier, although less precise.

My Bonneville bike has ceramic wheel bearings. I didn't notice a change in either smoothness or rolling resistance, although I didn't expect very much. I did it to try and gain any advantage possible. I did see a significant difference in engine performance when I rebuilt the motor with ceramic bearing, but the rpms are a lot higher. If you do use them, and if the $ isn't a huge issue I say go for it, make sure you freeze the bearing and get a heat gun on the wheel. They'll drop right in, and pressing the bearing in can (I've been told) crack the ceramic balls.