New member looking to build a 1200 or 1300

[Kawasaki Fan]

Hi guys, I am completing a ZG1000 Concours project with ZX11 pistons, GPZ900 cams and carburators, ported by myself, etc, and have been contemplating my next build as either a 1300 or 1200 cafe racer and any advice and sources for parts is appreciated.

I was looking at the ZN1300 frame and the appears similar to the ZG1000 up from the neck to the seat. Has anyone tried fitting a Concours tank to a ZN1300? I am assuming Kawasaki used the same jig.

The 6 cylinder 1300 is my preference but I've noticed the fuel injection components are scare on ebay. Will going with the 6 cylinder be a budget buster compared to the 1200? Can the fuel controller be tweaked to supply an engine with reground cams and free flowing exhaust?

I probably will go at this with a frame and engine purchase first unless a complete donor bike can be located in East Texas.

[SgtSlag]

Sorry. We're pretty much a ride it as they made it, crowd, here. The 1300's are not very common, like the 1200's were. There have been a few members here who have stripped the XII of its tupperware, to make a scream machine. Not sure if any modified the engines, though. Like I said, most of us just ride them as great touring bikes. I wish you the best of luck! Cheers!

[Kawasaki Fan]

I understand completely and appreciate the reply. One question though, has anyone ever matched up the carbs from a Concours to the intake boots of a 1200? Just by eyeballing the spacing APPEARS nearly identical. If they do match that opens up options since IMO the 1200 with the oversquare bore/stroke has vast potential to be a sleeper.
Stock 1200 carbs 30 mm Concours 32 GPZ900 34 (not pictured)

[SgtSlag]

Not that I know of. Would love to hear the outcome of your experiments, however. Cheers!

[GrandpaDenny]

The Concours carbs don't have overflow vents. Hydro lock is a known and common problem with them - raw fuel gets into the cylinders. So if you do manage to get C10 carbs to fit and work, use the VXII fuel bowls.

[Nails]

I didn't notice the increase in bore size. XII carbs certainly are small, but that contributes to the bike's ridability. "Constant depression" carbs have a characteristic lag, waiting for increased air flow to raise the piston and thus increase the fuel flow. Small carbs have less lag, and so they give a better off-idle "chirp" response. I think this factors into how the XII has a lot of torque relative to the HP. (A racer's motto: "trade me torque for HP and I'll beat you every time.")

To take an example, Yamaha put two carbs on some single-cylinder thumpers. One is a conventional CD carb, rather small. The other is much simpler (no idle circuit) that only opens with big throttles, augmenting the small "primary" carb to supply the high volume needs. Although accursed (it's a bitch to jet), I like the way it performs ... especially in low RPM technical riding.

In short, the XII isn't designed to scream. I'd be interested to hear how the motor responds. I suspect the result might not be quite what you expect, such as cross-purposes with the stock cam profile or other high-flow limitations/compromises. Maybe you'll pursue transplanting the heads too?

[GrandpaDenny]

"Constant depression" carbs

Perhaps some Welbutrin would help? Zyloft?

[Nails]

Tried that. Didn't work.

[Kawasaki Fan]

Yes the CV carbs can have issues, however I had a FJ1100 bored to 1314cc and everyone told me the stock carbs would be hell to tune but with the stage 3 Dynojet kit including lighter springs and drilled slides the carbs did fine, well enough to bury FZR1000 and ZX11. I'm a fan of big bore/short stroke engines because the vacuum signal is strong, the valves breath better (cylinder walls further away), and of course they rev quicker.

The intake ports will hinder max RPM power but my objective will be just as it was with the FJ: massive midrange.

ZG1200 specs

[Kawasaki Fan]

Can someone provide a link to a repair manual .pdf so I can check internal engine specifications?

[triton28]

Not sure if it is pdf but if you go to AVA Home page-select Tech Center-select Voyager XII you will get Page 1 of 2 and on this page the 2nd window down will link you to multiple manuals.

[GrandpaDenny]

Can someone provide a link to a repair manual .pdf so I can check internal engine specifications?

It's in my .sig below

[Nails]

Yes the CV carbs can have issues, however I had a FJ1100 bored to 1314cc and everyone told me the stock carbs would be hell to tune

I was talking about the bore of the carbs. I’m too lazy to look up Connie carbs, but I think they’re sized for higher RPM/flows than “mid-range”. I notice that stock XII carbs are the same size as much smaller bikes, including some Honda 250 4-cylinder racers IIRC.

Still curious to hear how larger carbs affect the XII’s power profile.