Holy fat Kaw Batman!!!

So I've come to the conclusion that my bike has a drinking problem. I'm currently running 20 pilots, 4th clip on the needles, and 120 mains in my vm26 carbs, with a MAC 4-1 w/ Kerker baffle, and K&N pods and she's still a touch on the lean side!!!! I'm going to have to bump to 22.5 pilots and 122.5 mains and might have to reclip to the 5th slot so she gets enough to drink!!!
I'm not even sure how this is possible since my brother in law has vm28s on his cb750 and he's running 17.5 pilots, center clip on the needles and 115 mains, same K&N pods and same exhaust (but with the MAC baffle not the Kerker).
Other than being just a little lean and not wanting to pull hard she's running great and starts every time on one kick, so I don't think there are any other issues causing this, just a thirsty damned Kaw I guess...anyone know anything that I might be overlooking?

Have sparkplug readings been done to confirm suspicion of lean running condition? Any differences among cylinders?

Has ample fuel supply to carbs been assured? With engine not running, and petcock on, fuel should flow steadily from open floatbowl drain screws.

Would use the clear plastic tube test to check floatbowl fuel levels. The service fuel levels may be too low and thereby requiring other components to be set rich in an effort to compensate.

Good Luck!

Float heights have all been checked with the clear tube method and the fuel flow seems to be okay. Plugs are all a little white, indicating an even lean situation on all 4 cylinders. Is it possible the stock petcock doesn't feed enough for the bigger carbs? I've got the stock 77 kz650 gravity fed petcock on there. I've also got a dual outlet pingel with the correct size adapter plate in my garage, if need be I could T those outlets together and try running the pingel but I'd worry that would be too much fuel...

What type VM26 carburetors are you using? You are already richer than a KZ1000 set up with a 4 into 1 and K&N pods would need to be jetted. What spark plugs are being used? The jetting on the VM26 changed radically from 1976 till they quit using them in 1978. Do you have air screws or pilot mixture screws? Also, a stock petcock flows more than enough gas for a VM26 which has little bitty diameter fuel pipes. What type gas mileage do you get? What type carb holders are being used?

The 26s are off a Suzuki GS750, not exactly sure what year because I got them from someone who got them from someone (one of those deals...). They have both pilot and air screws. Carb holders are new, stock style, bought to fit a 77 kz900 at the recommendation from this site. Using stock B7ES spark plugs. Also, no other engine mods other than the pipe and intake. Thanks for the help.

Also the pilot screws are out about 1 1/8 turn from snug and the air screws are out about 1 3/4 turn from snug. This is the configuration that makes it run best as it sits. I don't have an accurate gas mileage because I haven't run a full tank through it yet without spending a lot of time on the center stand dinking with the carbs, but the last tank I ran I was just a bit above 30 mpg (94 miles on just a shade over 3 gallons) but that wasn't all riding either, a lot of time on the center stand in the garage...

When fooling around with GS750 carburetors it is CRITICAL to look at the number stamped on the slide cut out. The earliest GS750 carbs had a P-1 needle jet (HUGE and makes tuning tough). They also used a 2.5 slide cut out and 25 pilot jet stock. I have NEVER had any luck tuning those things. After building about 11,787 of the GS750s, they started making them even more stupid to tune. They used an 0-6 needle jet and stuck #27.5 pilot jets in with a 1.5 slide cutaway. These things are so rich gas will drool out before they will run. At bike # 19,375 they wised up and started using #15 pilot jets, smaller air jets and the slide cutaway stayed at 1.5. These things became more tunable. They used the same 5F21 jet needle the whole time and clipped it to the 3rd slot.

Anyway, the specs on the early GS750s were truly bizarre and rendered them more or less un-tunable; especially the very early one with the huge slide cut out. Any of the later ones can be tuned.

When you come on here and start talking jetting, you had best talk about what type carb you have because ALL those GS750 carbs LOOK the same. Get the slide cut out and we can take a guess at jetting.

I'll get the slide cutout info and be back with that later tonight. I know that 15 pilots and 112.5 mains came out and the needles were clipped at 3 when I tore the carbs down for a rebuild. Now to venture out and get the slide cutout info.

Just pulled the carbs off and the slides out and they are 1.5 cutaways. So it would seem these are the later Suzi carbs and I might just get lucky enough to get them tuned?

Good! The stock main jet size is either #97.5 and #100 in typical wimpy Suzuki style. The stock pilot is a #15. The jet needle is clipped to the 3rd slot. I haven't seen the plugs. How white are they? Keep in mind you MAY be lean in one range but not others. With your bike, I would say #110 mains are about as far as you would need to go. We can speculate all day but the easiest circuit to tune is the main by doing a plug chop. Get a NEW set of plugs. Ride to somewhere safe to go fast. Install plugs and without sitting by the side of the road idling take the bike out and in 3rd or 4th gear ride it wide open for about one mile. Hit the kill switch and coast to a shady spot and pull you plugs. I bet they are sooty and dark and not lean. Most riding is done on the jet needle and some on the pilots. Once you get settled on the mains (I would try your big jets then some #110s), I would raise the jet needles a clip and look at the plugs again. The #20 pilots are already way big. With a #17.5 pilot, I would try the pilot mix screws 1 3/4 turns out and air screws 1 3/8 turns out. With your 20s, you are most likely pretty close. It isn't easy to tune the pilot mix screws so leave them alone and tune each of the air screws for max idle speed. Move the screw in and then out about 1/2 turn and LISTEN for the highest rpm you can get. Most of the time, the air screws don't have a huge effect.

Thanks for the help WG!!! I tore into the carbs, rejetted with 17.5 pilots and 117.5 mains, moved the clips to the third slot, set my pilot and air screws to the baseline you recommended and holy cow!!! I'm still dealing with just a little stumble off idle, not sure if I need to mess with the pilot screws or what now, but she's pulling like a scalded dog from just over 2500 through 10K now, running like she should. Now I'm completely baffled as to where my lean condition was coming from across all four plugs, unless I didn't have the pilot screws out far enough for the pilot circuit or something, but the fact that she's running right now is all that really matters. Thanks again WG!

The off idle thing will go away with some playing with the pilot mix screws or try adjusting the airscrews in if you don't want to fumble under the rack while it is on the bike. Sounds like you are a tad lean in the pilot circuit and could adjust the issue out... the fun thing about those Suz carbs are the great amount of adjustability with both sets of screws... I like Kaw carbs much better because the great adjustment in the idle circuit is kind of dumb in my humble opinion. Same as the 29 smoothbore. On a performance carb, why have a lot of adjustment in the idle circuit? The street carbs don't have as much and street riders care about smooth idle operation.