Kz750E2 running lean PLEASE HELP

baldy110 wrote: I'll be the bad guy here, you will never get it to run correctly with the exhaust setup you have.

I have no room for a 4 into 1 do you think 2 , 2 into 1s would do the trick I was gonna do that with 2 mufflers on the end I’ve pulled the baffles in and out of the exhaust bent them for more or less back pressure and still nothing changes is their some kind of sensor or something I’m missing the bigger it’s not a factory harness I built one for it it just gives power to the coils charges the battery using a new stator and regulator I installed I’ve checked and I have good spark and perfect battery voltage to the coils

JR wrote: Gravity fed fuel should not be a issue as thats the way the 750 fours operate.

What sort of petcock do you have? Is the flow restricted in any way?
Is the gas tank vented?

Is the fuel filter restrictive? Some paper automobile type fuel filters dont flow fast enough without a pump. A motorcycle one is best but even a cheap lawnmower one would be better than one designed for autos.

Have you checked you carb float bowl fuel levels? Search clear tube method here. Low fuel level in the bowls will cause lean running. Your carb bowl fuel level should be 4mm below bowl/ carb body seam and thats measured not eyeballed. Assuming carbs are keihin CV34 which came on the 750 E2. Getting my fuel levels correct was the single biggest improvement I made .

In an earlier post you mentioned cheapo snowmobile pods. If you look into the pods is there a lip which might obstruct and air intake on the carb? Although this would be more likely to cause a rich condition it might be worth checking.

There is also the possibility that the open header is the main cause of your problem but I have no suggestions for that one other than try a slip on silencer or keep trying bigger and bigger jets. 165 for the secondary main is already huge. You could up the primary 70, 80 90 ???

I’m running an automotive fuel filter but I’m also running the vacuum refranced fuel pump / petcock that came with the bike so I am getting fuel I set my float level at exactly the seam where the bowl meets the carb body (overspec) so it was even Ritcher it took me hours but like you said it’s very important

At wide open is the intermediate jet working with the primary to provide that fuel or at that point is it just using the main also the bike came with the cv34 without the plastic T In between numbers 1-2 and 3-4 the new set of carbs does have that plastic T it came with different slide springs and needles so I replaced them with the slide springs needles and emoltion tubes do you think that could be the problem the carbs I got where also jetted much leaner had like 95 main or something rediculous so I threw in my 145s

I'll say it again. You will NEVER get the CV carbs to run correctly with that setup. They will either run good down low or up high but not both. CV carbs are difficult to tune with good pods and a good 4-1 pipe. Using the exhaust setup you have it will be near impossible. I have tuned 100's of CV style carbs on all sorts of bikes and learned that they need a good exhaust to function correctly. There is no way around this except to get a set of manual slide carbs, VM, CR, RS, ect.. And there is no sensor and yes at WOT the carbs are running on the main jets. Good luck.

baldy110 wrote: I'll say it again. You will NEVER get the CV carbs to run correctly with that setup. They will either run good down low or up high but not both. CV carbs are difficult to tune with good pods and a good 4-1 pipe. Using the exhaust setup you have it will be near impossible. I have tuned 100's of CV style carbs on all sorts of bikes and learned that they need a good exhaust to function correctly. There is no way around this except to get a set of manual slide carbs, VM, CR, RS, ect.. And there is no sensor and yes at WOT the carbs are running on the main jets. Good luck.

I don’t have any room to build a 4-1 without it getting mashed flat from rocks do you think 2 2-1 will make it better if so I’ll build one and throw some baffles in it for back pressure

You said you are running an automotive fuel filter. That may cause problems, but usually it is fuel starvation. The vacuum petcock is not a fuel pump. It is a simple valve that is either open or closed, depending on whether or not it is getting vacuum.
I appreciate the packaging difficulties you face, but a proper exhaust system is much more than some random tubes taped together. There is no constant pressure in the exhaust. When the exhaust valve opens, high pressure gas enters the pipe and travels down the pipe, through a collector, a mid-pipe, and a muffler , on its way to atmosphere. Behind that pressure wave, a low pressure area forms that helps scavenge the combustion chamber, allowing it to fill with a fresh charge. Complicating this elegant maneuver is a reversion wave. Once the high pressure wave exits the system, atmospheric pressure enters the system to equalize the pressure in the pipes. If this reversion gets to the exhaust valve before it closes, it can actually push some of the air-fuel mixture back into the carburetor, normally resulting in a lean mixture.
In general, shorter pipes will only work at higher rpm. The shorter, the higher, longer lower.
A collector allows for a broader rpm range of happy pressure pulses since the individual pipes can help scavange each other and reversion waves can be reduced.
As mentioned above, CV carbs are very sensitive to all this since the slides are wholly dependent on having proper pressure signals.
You have introduced a bunch of variables, all of which affect others. Mechanical slide carbs will eliminate some of the problems, but getting the engine to produce full power throughout the rev range, with crisp throttle response and smooth running, will likely take a great deal of experimentation.

TexasKZ wrote: You said you are running an automotive fuel filter. That may cause problems, but usually it is fuel starvation. The vacuum petcock is not a fuel pump. It is a simple valve that is either open or closed, depending on whether or not it is getting vacuum.
I appreciate the packaging difficulties you face, but a proper exhaust system is much more than some random tubes taped together. There is no constant pressure in the exhaust. When the exhaust valve opens, high pressure gas enters the pipe and travels down the pipe, through a collector, a mid-pipe, and a muffler , on its way to atmosphere. Behind that pressure wave, a low pressure area forms that helps scavenge the combustion chamber, allowing it to fill with a fresh charge. Complicating this elegant maneuver is a reversion wave. Once the high pressure wave exits the system, atmospheric pressure enters the system to equalize the pressure in the pipes. If this reversion gets to the exhaust valve before it closes, it can actually push some of the air-fuel mixture back into the carburetor, normally resulting in a lean mixture.
In general, shorter pipes will only work at higher rpm. The shorter, the higher, longer lower.
A collector allows for a broader rpm range of happy pressure pulses since the individual pipes can help scavange each other and reversion waves can be reduced.
As mentioned above, CV carbs are very sensitive to all this since the slides are wholly dependent on having proper pressure signals.
You have introduced a bunch of variables, all of which affect others. Mechanical slide carbs will eliminate some of the problems, but getting the engine to produce full power throughout the rev range, with crisp throttle response and smooth running, will likely take a great deal of experimentation.

I stared to take my headers and build true duals for it with some length I have no where to put a 4-1 collector the only question I have is should I run a baffle because a simple perforated tube muffler with packing is gonna provide no back pressure it’s the same diameter as the exhaust tubing it just obsorbs sound when building it I made shure I have at least 1 good 90 degree for pressure as well as another Bend tword the end. my exhaust is not just trown together I build individual headers with baffles I’m a certified welder fabricator. i just need to know if a 2-1 with 2 good bends from after the header the original 4-1 only had 1 90 before it became straight

And also I do know quite a bit about exhaust scavenging since I usually ride 2 strokes I just figured since you have a full stroke pushing out your exhaust the scavenging effect would not come into effect

I am pretty sure the engine you have came from the factory with a 4 into 2 exhaust with a crossover under the sump. Perhaps you can replicate the diameter and length of each side of the factory setup, omitting the crossover. That might get you close enough to get it running better .
I wish OMR was still around. I reckon he has forgotten more about this than I will ever know.

TexasKZ wrote: I am pretty sure the engine you have came from the factory with a 4 into 2 exhaust with a crossover under the sump. Perhaps you can replicate the diameter and length of each side of the factory setup, omitting the crossover. That might get you close enough to get it running better .
I wish OMR was still around. I reckon he has forgotten more about this than I will ever know.

By the way really like the Borg profile pic star trek is the shit

Trek can be as deep a rabbit hole as an old bike. My wife is a Trek prop and costume collector.