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Discussion Starter #1
So, I hit reserve on my second tank with the new bike yesterday. 115 miles before reserve. I know this is really bad.

As far as I know, everything is stock. Tire size and pressures are correct, alignment is correct according to Fog's string procedure. No popping on deceleration. Idle is not rock steady, but only fluctuates 50-100 rpm. Bike starts right up in morning on first crank. I do ALL city driving, which means stop every other block, mostly 40 mph. The other thing is that my drive to work is 10 minutes long, and the bike gets warm about half way there. I know that both of those factors hurt. Also, I usually run about 7-8K rpm.

I have not pulled the plugs yet to see their color. I am just confused because I didn't think that with the bike running this well, that you could get this bad of gas mileage. What are the possible causes that I should check for?

I am assuming that the bike doesn't have a jet kit because the brass caps are over the idle screws and the stock exhaust is still on. This may be a bad assumption.
 

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I'd ride it a while and make sure there's actually a problem. If you are using the fact that you changed to reserve as your indicator, it may be in error. How full was it? The error might be there. Monitor the gas amount you put in and the miles travelled as your indicator, not when you went on reserve, and do it over several tanks, several hundred miles.

As you related, it's hard to imagine that a nice running engine could have a dramatically lower than average mileage.

Good luck.
 

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First get some real data. Reset the trip counter at fill up and check the consumption accurately divide the miles driven by the number of Gallons used and get a reliable figure in how many miles per gallon your actually getting. do this for at least three fillups. A low should be about 40 mpg. for that type of driving. If you are well below that number you should start looking.
The plugs arn't going to tell you much except what you already know. Look to be sure your choke is returning to off. On the good running: After the bike is fully warmed will it run smoothly at a steady light throttle setting. If it stumbles then your floats are too high or stuck.

A bunch of other things are still possable too

FOG
 

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Discussion Starter #6
I have not pulled the plugs since servicing the bike when I first bought it. I put in new plugs at that time (300 miles ago).

Choke not turning off may be a good idea.

Just for reference, I got 35 mpg on the first tank, and hit reserve at around 110 miles, same as this tank. I just assumed then that I was getting around the same mpg.

It does run smoothly at all throttle inputs.

I refuse to believe the way I ride the bike would result in 35mpg. I have searched all of the gas mileage threads, and only bikes with problems were getting this low.

Are the jets marked? If so, if I pull them, what sizes should I expect to see for a stock configuration?

For other possibilities, the brakes don't drag, the chain tension is correct, the bike doesn't dump fuel, and gas is not going into the oil. I think FOG is on the right track that the carbs are putting in too much fuel. For my education, will a bike that is too lean suffer in gas mileage?
 

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You can check if sombody put a jet kit in, by removing one of the Black plastic carb tops and pull the needle. If it's a multi position on with a C clip there is a jet kit and a badly installed one at that.
The Stock needle had a fixed head. If that's what you have there is not a jet kit.

I'm still more inclined to think "carb problem". While the plugs will affect the milage somwhat, not enough to lower the milage that low with out some other symptoms too.

FOG
 

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Discussion Starter #8
FOG, is it possible that a lean condition will cause gas mileage to go down? I am assuming so, but would you notice performance problems before that happened?
 
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Lean would make mileage go up, the only thing that should really affect is engine performance.
 

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Discussion Starter #10
Just refilled again today. 28 mpg. ??? I am going to be doing some investigating tomorrow.
 

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This thing can't be running good, The only thing that comes to mind is a compound (but quite common) problem of a leaking petcock, and a partially open float valve in one of the carbs. This will allow the gas to run into the engine unchecked when the bike is parked. When the float bowl overflow the excess going into the engine via the intake runner and past the intake valve into the crankcase. Check your oil for gas.
The same fault will usually make the bike stumble or hunt at steady throttle settings. You say no but,,, At 28 Mpg the thing is running so fat you probably can't tell, or don't know the difference.

FOG
 

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Discussion Starter #12
There is no gas in the oil. I have watched the oil level carefully, and it has not increased at all. I just pulled off the tank, and the petcock is not leaking at all, I tried all of the settings. There was no gas dumping from the carb overflow. To compound it all, the spark plugs are showing lean. The ceramic is as white as brand new, and there is just a tiny tan film on the electrode. The exhaust smells of gas. In addition, it is popping pretty good when I let off the throttle suddenly.

The best that I could come up with was a gummed up air filter for running rich. I cleaned it and re-oiled it. No change. I also balanced the carbs. No change.

I don't understand why the spark plugs are white, but everything else is pointing to running rich. I am now thoroughly confused.

Could it be that one of my floats has gas in it? That would flood the engine, but if the petcock is working right, it wouldn't get gas in the oil.

Is there anybody in the DFW area that has an EX500 that would ride it and let me know if it is running badly?
 

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Discussion Starter #13
Forgot to mention two things:

I turn my petcock to off every time I get off of the bike. I know this won't preclude gas flooding, but it reduces the chances greatly. Also, I pulled the cap off of one of the carbs, the needle was not notched. It didn't have a clip on it.

I did a valve adjustment when I got the bike too. I guess that could have screwed it up too. But I don't think it would cause gas mileage that bad. Would it?

So, what is your take on the cause?
 

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I know this is an old post but I think I am having the same problem and wondering if you ever got it resolved. I just did an oil change after I noticed hesitation around 3k RPMs. I got some seafoam and put it in the tank. I have been riding for about 2000 miles and getting around 58 mpg. Today, on the first tank of seafoam and the first tank after the oil change I had to switch to reserve at 120 miles, only 30 mpg. I checked the oil level and it does look like it got higher, and indeed the oil smells of gas.

Another symptom: Recently, probably around the same time I noticed hesitation, the bike was idling low and took at least thirty miles of riding to go to the right idle speed. I adjusted the idle speed to be a little higher, so now it starts at 1200 but then after about 30 miles it will go up to 1600. I know that might be bad but I have probably only ridden 100 miles like that.

Are these symptoms pointing to a stuck float valve? Or leaking petcock, or both? If this requires a carb cleaning I will probably have to take it in to get serviced because as much as I would like to clean the carbs myself, living in an apartment in the city makes that tough. But, if I need to I will.

One last thing, will I have to change the oil again if I stop the leak? I can't imagine gas in the oil is a good thing for the engine.

Thanks!
 

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Your problem does not sound like the OP's problem. If you have a piece of clear hose, you can do a test as shown in the diagram below which is in both the Clymer and Kawasaki factory manuals to determine the fuel level in the bowls with the carburetors still on the bike. The level should be 0.5 mm +/- 1 mm above the lip of the bowl.

The OP's problem might have been caused by a punctured diaphragm in the petcock. I worked on a bike which never required choke because a hole in the petcock diaphragm allowed the vacuum hose to the petcock to suck fuel through the diaphragm directly into the left intake bypassing the carburetor altogether as shown in the photo.
 

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Thanks so much for that info. I'm going to get some clear tubing this weekend and check that out.

About the petcock: I was just recounting my problem to a friend and I remembered something... when I ran out of gas today and flipped to reserve I felt like the bike was running much better. So much so that I was thinking the seafoam must have cleared up the blockage and for some reason that stalled the engine (I know that doesn't really make sense but I was trying to think positive haha). I also just remembered that when I bought the bike the petcock was flipped to reserve already. I'm starting to think that it has been a petcock issue all along. Do you think I could have not noticed this all along? It doesn't really explain the sudden drop in MPG though.

I'll search the wiki for some petcock troubleshooting and let you know how the inspection goes.
 
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