really need help!

so i picked up a 79 kz750, i no my screen name doesnt make sense, i spelled it wrong.any way
i am having some problems with it running. it ran great when i first bought it and a few days after i started having problems. ill start off with this.

when i first got it i had to run with the choke all the way on.

started tinkering with it. ended up cleaning the float bowls,needle, seat,there was i think a jet in the bowl that unscrews also that i cleaned. changed the spark plugs and ran great! ended up putting sea foam in the tank like the directions called for and started acting up again. popping from the exhaust, sputtering, no lowend power, but when i would give it some gas and open it up a bit it would run fine. so today this is what i did (carbs were rebuilt two years ago by previous owner) i do believe him cuz all the parts looks great!

cleaned the bowls and everything again. new plugs, adjusted the floats (noticed one float was adjusted different then the other one so thats why i adjusted them)and checked them with the clear tube method, adjusted the pilot screw to the specs in the manual. with all of that i got the bike to idle with the choke being completly off. but still hesitates and sputters. no popping though. everything is stock on the bike. exhaust ect. one thing i did notice though is i have about a 1/2"x1/8 wide hole in my exhaust before the muffler. could this be causing me problems with the way it is running? kinda of make sense to be cuz when i give it good throttle and picks up and runs great! i dont no what else to do but weld this hole and hope for the best. any help would be greatly appreciated. sorry for such a long post

How much Seafoam did you add and how much gas was in the tank after you added it? Ed

there was about half a tank and i only put about 1/4 can of sea foam. so not really what the directions said but ive used it like this before with no problems. not on a motorcycle before though

when i first got it i had to run with the choke all the way on.

Sounds like a lean condition. Although your exhaust leak is probably contributing to the problem you probably have an intake leak. Check your carb boots and manifolds and your airbox. Any air leak in the OEM setup will cause the problem you are describing.
Terry

will do terry. any other suggestions?

I am having very similar problems.

Looking forward to following advise posted now and in the future.

newowner79kz750b1 wrote: there was about half a tank and i only put about 1/4 can of sea foam. so not really what the directions said but ive used it like this before with no problems. not on a motorcycle before though

I wouldn’t change anything until I made sure it wasn’t a fuel problem, and the good news is this is really easy to try. Seafoam instructions say 1 oz. per gallon. If you added 1/4 can that's 4 oz. if that was added to 1/2 tank (that’s about 2 gallons) of gas (or less). The mix at that point was at least double the recommended strength. If your estimates are off a little the ratio may be even further off. I would drain that fuel and put it in my car or truck and fill the bike's tank with fresh gas. If you're lucky, the problem will be solved without any further action needed. Seafoam is good stuff, but too much can make the gas burn inefficiently. Ed

Is there a fuel filter in the line? If not, crud from the tank could be clogging up the carbs. If you're going to drain the tank anyway, take a peek inside with a flashlight. It might also be worthwhile to pull out the petcock to check for crud on its filter screen.

One more possibility, only because it sounds so familiar.
When I first bought mine about five years ago, my #2 carb was having serious problems just like yours. I dropped the float bowl, cleaned it up and all that, but nothing I did would fix it. I did everything possible while trying to to avoid removing that dreaded air box. I sprayed WD-40 all of the place looking for a vacuum leak, nothing. Even futily cleaned and oiled the advance weights and chanting incantations to the gas gods. But nothing. Sometimes it ran great, other times, like crap.
Finally I decided it was time to bite the bullet and remove the air box and the carbs. When I did, I was both totally shocked, pissed off, and relieved at the same time.
Right before my eyes I instantly discovered my problem.
Somehow, the PO managed to jam the carbs back on while simultaniously folding over the edge of the #2 carb boot. The thing was sometimes sealing itself, and other times it was just sucking air.
When it comes to used bikes, Forest Gump said it right. "Sometimes ya neva know whut ya gonna get".

So check your carb boots. And check them for cracks while you're at it.

Didn't have much time to work on the bike today because of work but I did pull the exhaust off that had the hole. Come to find out the hole is bigger then what I thought. The hole is before the muffler and is a good 1"x1" hole. I'm kind thinking that might be what is causing my problems?

oil the mechanical advancer

since the bike is all stock from what i can tell as far as motor carb wise then i think i have stock jets so i dont think its the jet size. i also can get the bike to run with out the choke so i dont think that is it. i have the pilot screw 1& 1/2 turns out. so i think the only thing it can be is the floats or blocked passages. so ive been obsessing over this manual and online since my bike is at a friends there for i can only work on it on the weekends (tue wed) and from what ive read the pilot screw controls 0-1/4 throttle. i can get the bike to idle fine but ill give it gas and it will go and sputter but full throttle will go just fine! so according to my book then the jet needle position control 1/4-3/4 throttle which my problem is in between. so like 1/4- 1/2 so is the jet needle what the tang on the float rests against? so with all that being said any other ideas. tuesday gunna look at the tank and petcock. i have my exhaust off right now so that i can weld the hole up. then check for air leaks around the carb. from looking at the boots around the carbs they look great and r soft to the touch. if i have a hole big enouh in the exhaust couldnt that make me loose backpressure and run rich?