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TOPIC: Kz750E2 running lean PLEASE HELP

Kz750E2 running lean PLEASE HELP 28 Feb 2019 06:57 #799389

  • Goldmam
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So I have a kz750E2 swapped quad it breaks up at 6-7 grand I thought it was because I had resistor plugs with non resistor plugs so I replaced the wires and plugs and ran it. Some other info the bike has open headers and pods so I jetted it up to 145 my float level has been set perfect to spec and my ignition has been gone over as well mechanical advance works great everything else checks out perfect battery voltage to coils even shunted the wire to the coils. So after all this I rode it and pulled a plug after the same issue and the plug was white and ashy (leannnnn) so i jetted it up to a 165 still no change I think my tank might be the issue it’s gravity fed and if the fuel is low at all the fuel filter won’t fill till I sit on the back and the gas moves to my petcock. Has anyone had issues with gravity fed tanks i have the stock petcock/fuel pump should I run that for some better fuel flow I’m confused on how it runs lean with a 165 please help
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Kz750E2 running lean PLEASE HELP 28 Feb 2019 10:03 #799396

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You must use some kind of air filter with those keihin cv34 carbs. Jetting with pods is 35-65-140.
Kawasaki KZ 750/4 LTD 1981
Kawasaki KLR 650 2011
Argentina - Buenos Aires

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Kz750E2 running lean PLEASE HELP 01 Mar 2019 07:50 #799460

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undiablo wrote: You must use some kind of air filter with those keihin cv34 carbs. Jetting with pods is 35-65-140.

I do run pod filters at all times I just ran it like that to see if they where restricting the air flow if you read what i said it’s still running lean with pods and 165 main jet

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Kz750E2 running lean PLEASE HELP 02 Mar 2019 07:35 #799519

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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 ???
1980 kz750E1, Delkevic exhaust

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Kz750E2 running lean PLEASE HELP 02 Mar 2019 18:40 #799546

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Two things you need

1] DynoJet jet kit for the KZ750H/E
2] Uni or K&N filters.


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81 KZ750e
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www.dotheton.com/forum/index.php?topic=39120.0


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Kz750E2 running lean PLEASE HELP 02 Mar 2019 19:34 #799552

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Nebr_Rex wrote: Two THREE things you need

1] DynoJet jet kit for the KZ750H/E
2] Uni or K&N filters.
.


3] Mufflers (or at least in pipe baffles)

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Last edit: by Nessism.

Kz750E2 running lean PLEASE HELP 04 Mar 2019 08:24 #799671

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Nessism wrote:

Nebr_Rex wrote: Two THREE things you need

1] DynoJet jet kit for the KZ750H/E
2] Uni or K&N filters.
.


3] Mufflers (or at least in pipe baffles)

The bike is jetted up already I have uni filters and my exhausts have baffles I think I might have skipped cam timing a tooth I’m pulling the motor out today to check the valves and the cam timing

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Kz750E2 running lean PLEASE HELP 04 Mar 2019 08:27 #799672

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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 cut the lip off the filters already that was the first thing I did and they don’t make the primary jets so I drilled an extra set I had and still no change the thing is jetted fatttttt and it’s still lean could it maybe have gpz cams or something it does idle with a lot of lope it barely wants to idle

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Kz750E2 running lean PLEASE HELP 04 Mar 2019 16:47 #799723

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You posted conflicting information about your filters.
The UNI filters for that engine do not have a lip.
Quit being so obstinate. If you have the correct filters all you need is jet kit.
A constant velocity carb takes more than just jets to be jetted .
With a jet kit all this has been figured out.


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2002 ZRX1200R
81 GPz1100
79 KZ1000st daily ride
79 KZ1000mk2 prodject
78 KZ650sr
78 KZ650b
81 KZ750e
80 KZ750ltd
77 KZ400/440 cafe project
76 KZ400/440 Fuel Injected

www.dotheton.com/forum/index.php?topic=39120.0


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Kz750E2 running lean PLEASE HELP 04 Mar 2019 17:58 #799732

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

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Kz750E2 running lean PLEASE HELP 04 Mar 2019 19:57 #799740

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they don’t make the primary jets so I drilled an extra set


They do
www.z1enterprises.com/catalogsearch/result/index/?p=2&q=Keihin

Stock jetting is pilot 35, primary 62 and secondary 125 which i assume is the one you drilled to 165.
With K&N pods and a 4 into 1 exhaust 35, 62, 140 should work. I have used 35, 70, 140

As i said earlier the open header is probably your main problem.

I think, not totally sure , that the gpz exhaust cam does not have a tach drive for a mechsnical tach
1980 kz750E1, Delkevic exhaust

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Last edit: by JR.

Kz750E2 running lean PLEASE HELP 05 Mar 2019 04:54 #799750

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JR wrote:

they don’t make the primary jets so I drilled an extra set


They do
www.z1enterprises.com/catalogsearch/result/index/?p=2&q=Keihin

Stock jetting is pilot 35, primary 62 and secondary 125 which i assume is the one you drilled to 165.
With K&N pods and a 4 into 1 exhaust 35, 62, 140 should work. I have used 35, 70, 140

As i said earlier the open header is probably your main problem.

I think, not totally sure , that the gpz exhaust cam does not have a tach drive for a mechsnical tach


Then it’s not the cams cause my worm drive for my tach is still their and I did not drill the mains I had 165 main jets the ones that where 125 stock I drilled my intermediate jet that was a 62 but still no change I cut the tiny lip off the filter ( their was one but not enough to cause problems but I cut it to be safe) I’m pulling the motor to check Valves and cam timing as well as doing a leak down test

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Kz750E2 running lean PLEASE HELP 05 Mar 2019 04:59 #799751

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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

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Kz750E2 running lean PLEASE HELP 05 Mar 2019 05:08 #799752

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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

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Kz750E2 running lean PLEASE HELP 05 Mar 2019 05:16 #799753

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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

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Kz750E2 running lean PLEASE HELP 05 Mar 2019 16:23 #799795

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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.
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Kz750E2 running lean PLEASE HELP 06 Mar 2019 06:42 #799813

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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

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Kz750E2 running lean PLEASE HELP 06 Mar 2019 08:43 #799817

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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.
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Last edit: by TexasKZ.

Kz750E2 running lean PLEASE HELP 07 Mar 2019 05:54 #799849

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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

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Kz750E2 running lean PLEASE HELP 07 Mar 2019 07:46 #799853

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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

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