Fuel economy and a bigger tank?

I'm not satisfied with the combination of low fuel economy and small tank on my KZ750-H3 LTD... This bike left the factory with entirely too small of a tank for only 30-35mpg. I need a bigger tank. What kind of tanks will fit? I can't find this information on Google anywhere. A friend suggested a two piece tank meant for a Harley but I don't know if that'll fit...

We have a group of KZ lovers locally but they only ride at the local drag strip, So when I asked them they were like "uh... we never gave it any thought since all we ride KZs for is kicking butt on the track"

You should be getting better than 30/35 mpg.
Check tires and inflation, chain and sprockets and a full engine service
including a reshim of the valves. That should cover any maintenance
issues. Then there are changes that can be done to improve engine efficiency.
Anything to lessen the load on the engine. Including the right wrist.


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Should be getting around 45 mpg average.

The 750E tank (about 4.2 gals) has been reported to be a direct bolt-on but the triple tree will bang against it. a possible fix is to install a collar on the steering stop peg, but when pushing/maneuvering the bike around, you won't be able to turn the bike as tightly. I don't think any other tank is a direct fit.

Nebr_Rex wrote: You should be getting better than 30/35 mpg.
Check tires and inflation, chain and sprockets and a full engine service
including a reshim of the valves. That should cover any maintenance
issues. Then there are changes that can be done to improve engine efficiency.
Anything to lessen the load on the engine. Including the right wrist.

Tires are brand new. Inflation is factory recommended. Chain and sprockets are brand spanking new. Don't know about the valves, but the engine sounds and runs extremely good. Front end even picks up off the ground on hard acceleration despite the previous owner telling me the bike is too heavy to do that...

I think I found at least part of my problem... My petcock doesn't allow fuel to flow in the ON or RES setting, only in the PRI setting, and then the fuel leaks out if the bike sits with it on PRI...

Also, I had been hauling a passenger around a bit yesterday... Two passengers actually (not both at once, obviously)... Yesterday was the first time I ran out of gas since the first time I filled her up after getting her road worthy... and I was trying to see how many miles she's got per tank in case the fuel light doesn't work (at the time it wasn't even hooked up, but I don't know if still works).

Of course it also doesn't help that my speedo cable broke the night before last (at 75 miles on the trip counter). I ESTIMATE it was close to 20 miles when I ran out of gas, with the last 10 of those being with the first passenger. As a side note, this bike is very difficult to push up even a slight incline alone, Glad I had a passenger to help at the time it ran out of fuel. It was only like push it a block and then through a parking lot to get more fuel. So thankful it happened where it did too.
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martin_csr wrote: The 750E tank (about 4.2 gals) has been reported to be a direct bolt-on but the triple tree will bang against it. a possible fix is to install a collar on the steering stop peg, but the turning radius will be reduced for pushing/maneuvering the bike around. I don't think any other tank is a direct fit.

Hmmm... I remember trying a seat pan from a 750E and it didn't fit right. The hinges and latch fit, but it sat off the tank a bit, wasn't a clean fit basically... Also tried a CSR seat pan... hahahaha latch and hinges fit again but they sat up an extra 2 inches from the frame and the rubber feet on the bottom of the pan didn't even contact the frame as they're supposed to.

But I believe you about the E... I'm tempted to buy an E's tank and see how it works out. I'll talk to a local mechanic/KZ friend about it and see how feasible he thinks it is, or if he knows anybody who can fabricate a tank without charging an absolute fortune.

As for turning radius, isn't reducing that a good thing for pushing it around and moving it around at low speed? Or do you mean reducing the maximum steering angle?

If not hot dogging around, I was able to get between 45-50 mpg on my KZ750B.
30 mpg is rediculous.

Setton wrote:
I think I found at least part of my problem... My petcock doesn't allow fuel to flow in the ON or RES setting, only in the PRI setting, and then the fuel leaks out if the bike sits with it on PRI...

As a side note, this bike is very difficult to push up even a slight incline alone,
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martin_csr wrote: The 750E tank (about 4.2 gals) has been reported to be a direct bolt-on but the triple tree will bang against it. a possible fix is to install a collar on the steering stop peg, but the turning radius will be reduced for pushing/maneuvering the bike around. I don't think any other tank is a direct fit.

But I believe you about the E... I'm tempted to buy an E's tank and see how it works out. I'll talk to a local mechanic/KZ friend about it and see how feasible he thinks it is, or if he knows anybody who can fabricate a tank without charging an absolute fortune.

Leaking petcock and dragging brakes will mess suck up some fuel.
And even the side covers interchange. The KZ750H [LTD] frame kicks up in the rear and the KZ750 E [standard] is more flat.


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Check the strainer in the tank. If it's starving for fuel you'll be into the throttle more and the milage will drop. Check the cap vent as well. I just came home from a 100 mile trip. I replaced my filters up there and I could tell the bike was running better and my mileage came up. I'll be checking my cap tomorrow.
Steve

Nebr_Rex wrote: Leaking petcock and dragging brakes will mess suck up some fuel.
And even the side covers interchange. The KZ750H [LTD] frame kicks up in the rear and the KZ750 E [standard] is more flat.

The petcock isn't leaking. It's just not delivering fuel in the ON or RES setting. It only delivers fuel in the PRI setting. However, the carbs end up leaking fuel out of their overflow vents if I leave the petcock set to PRI after I park the bike...

I also very frequently have a smell of gas when the bike is parked. I'm thinking it's the PRI setting on the petcock because earlier today I caught the carbs dripping gas out of the overflow vents.

When I first bought the bike, there was a problem with the airbox filling up with fuel. That I suspect was happening because the carbs were absolute garbage when I got the bike. I had Wired George totally redo them though, and they're fine now.
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swest wrote: Check the strainer in the tank. If it's starving for fuel you'll be into the throttle more and the milage will drop. Check the cap vent as well. I just came home from a 100 mile trip. I replaced my filters up there and I could tell the bike was running better and my mileage came up. I'll be checking my cap tomorrow.

Strainer? Judging by the first video, I think you mean the filter... I bought a fuel filter back when the tank was rusty, but I recently ran a rust converter through it and then gelled the whole tank to seal any possible leaks and protect it from further rust. So I kind of neglected to put a fuel filter on in the first place.

As for the cap vent, it seems to be fine to me.

I'm pretty sure the engine's not starving for fuel, given how very fast the bike is...

Also... sometimes I hear a hissing coming from the bike when the engine's off. I'm not sure what that's about, nor am I sure yet where it's coming from. I suspect the tank.

You state "the carbs end up leaking fuel out of their overflow vents if I leave the petcock set to PRI after I park the bike" and "I had Wired George totally redo them though, and they're fine now.". If they leak at all under any circumstances they are not fine - there is a carb problem if they leak fuel regardless of the petcock setting.

Fuel coming out of the overflow hose (the little hose on the bottom of the carb) is the common symptom of the 3 possible problems described below. Remember - NO SMOKING or other activities that could ignite the fuel while working on carbs!

The float valve is not sealing. This may be (and probably is) just a matter of some minor dirt in the float valve and is very simple to remedy and can be done with the carbs still on the bike. Turn off fuel; drain carb by loosening big brass screw near bottom; and remove the 4 little screws on the bottom of the carb bowl. This will enable you to remove the carb bowl. You will then see the float. If you carefully remove the float you will see a stubby little needle that mates with a brass orifice; together, these two pieces are the float valve. Assuming there is no obvious damage to the needle or seat, use a Q-tip and some carb cleaner to clean the seat of the orifice and the needle. Be careful not to bend the tang that is attached to the float. This tang is the piece that the bottom of the float valve needle rests upon, and it determines the fuel level in the bowl, so bending it will change the fuel level. With the float valve cleaned it should no longer leak. To prevent a re-occurrence a quality inline fuel filter should be installed between the fuel tank and carbs. If there was damage the needle and seat should be replaced as a set; they are available.

The brass overflow tube inside the carb bowl is damaged. When you remove the carb bowl you will see a brass tube attached inside and rising toward the top of the bowl. This is the overflow tube and it leads directly to the overflow nipple on the bottom of the carb. Normally, the fuel level within the bowl rises somewhat close to the top of this tube. If the tube becomes cracked or separates from the bottom of the carb bowl fuel will flow through it and out through the overflow hose. Checking the condition of the tube is very easy after you have removed the carb bowl from the carb. Simply hold the bowl level and fill it up near the top of the tube with water or alcohol and see if it leaks. A slight crack in the brass overflow tube can be difficult to find. You can connect a rubber tube to the overflow nipple, fill the bowl with water, put finger over the open end of the brass overflow tube and blow in the rubber end and look for bubbles. If it does the best remedy is to replace it although some folks have found creative ways to repair them.

The fuel level is set too high. This condition occurs when someone has bent the float tang as mentioned above. This condition can be checked using what is referred to as the "clear tube test." The test involves attaching one end of a clear piece of flexible tubing to the carb drain hole and holding the other end of the tube above the bowl/carb joint. When the fuel is turned on it should rise in the tube to a level 2.5 - 4.5 mm below the bowl/carb joint. If the fuel rises higher than that level it may run into the cylinders or over the upper end of the brass overflow inside the carb bowl (mentioned above) in which case it will run out the overflow hose. This condition is corrected by removing the float and gently bending the tang to raise the float valve needle position. Doing this may take several tries before achieving the desired fuel level.

Correcting each of these three conditions involves removing the carb bowl. This task can be made easier if a short screwdriver bit is used, and depending on which carb you are fixing a mirror may help you locate the screws on the bottom of the carb bowl. Also, it is not a bad idea to have a new carb bowl gasket available in case the old gasket is damaged while removing the carb bowl. Ed

The petcock should have a strainer screen on it. Noise coming from the tank means a restricted vent. Clear tube test the float bowls. Too high your milage will suffer. Sync the carbs by vacuume.
Steve

Do you have a vacuum hose hooked up to the petcock? If not, it will not operate properly. Some owners will mistakenly remove the hose and use PRI as the ON position and one of the others as OFF, rather than fix a leaking petcock. If that is the case, you need to carefully clean it and replace the old rubber bits. Genuine Kawasaki parts are best in this case. 650Ed seems to have the rest covered.