Fuel Economy

Ok, here's the deal. I have an 82' XJ650 Maxim for 3 years now. After the 1st year I rebuilt the carbs and she has been running like a champ ever since. She still runs very strong now, but recently the fuel economy has done a downward spiral. It's gone from getting about 130 miles a tank to getting 90. Any maintenance suggestions to get her back up since gas is $4+ a gallon or soon will be? Thanks guys. :?:

 

Only $4? It's $4.50 here............ Have you checked your air cleaner, plugs to see if the bike is running rich? Have your riding habits changed?

 

I ride a little more aggresive than I used to, but not really that much. I haven't checked the air cleaner, I'll check it tonight. Plugs were my first thought too, so I pulled them and they looked fine, but just for GP I put in new ones like I usually do the beginning of every riding season. For $10 it just makes sense to change out every year. I'll let you know how the air filter looks tonight. 8)

 

I bought a spark plug cleaner from snapon saved me about 100 dollars a year in plugs, 2 dirt bikes, 3 three wheelers , 8 sleds, 2 bikes , clean them 2 times then get new ones. haven't had a problem yet .

 

Ethanol doesn't help...

 

Guys, I need some help. I just calculated my fuel econamy and it really really sucks.

I have a XJ550 Maxim, and I believe it's close to a 5gallon tank. Right now, I am getting 120Km before I have to fill her up. (That's about 75 miles for 5 gallon), in other words, I am getting 15 miles per gallon. What in the world could be causing this?

 

Have you checked your crankcase to see if there is a Gasoline smell? Have you checked your plugs? You are running really rich or leaking gas somewhere.............

 

No, I don't smell any gas in the crankcase, and I pulled my plugs and they are white and black, so no, I am not running rich.

 

Just a Thought

my tank is a 3.7 gallon tank my reserve is 1.7 gallons but if i never switch to reserve and think I am out of gas i would also assume my MPG has taken a nose dive right?

 

It's hard for me to imagine a bike running well and getting such poor fuel economy.
The fuel has got to be going someplace.
Running that Rich would be evident looking at the Plugs.
They would be close to fouled.

My first inclination is to ask you to check your Math!
I can't see that much Gas getting used in such a short time unless your Main Jets were so big as to almost flood the mill.

Are you sure you did the calculations correctly?
Have you taken-off the Oil Filler Plug and smelled Gas in the Oil?
Do you have a leak?

Did you rejet this Bike to accommodate Air Cleaner Pods?
Look at the Carb overflow hoses and see if there is evidence that you have a stuck Float.

15 Miles per Gallon I could understand if the Engine was a SuperCharged V-8.
I can't get my brain around 15 Mile per Gallon on a XJ-Bike without there being a problem easily detected.

 

Math is good, I am getting about 120Km before I have to switch to res.

I have smelled the oil, and it does not seem that there is any gas in there - it's hard for me to tell the difference, but I also got my dad to smell and he does not think there is anything not normal.

The bike has a stock air system, other then a hole in the air box about 2" in diameter.

I am unsure how to check the carb floats...

The only thing I changed was the angle the tank rests on the bike, but I don't think that should have changed anything.

I have included a picture of 1 plug that represents them all.

 

Damn ...

If anything ... you're running LEAN!
Look at the ceramic around the Center Electrode ...
It's CLEAN!

You should have some color on there.
Something ain't right.
Those are Plugs that show you are running on the Lean Side of life ... NOT Rich.

Back to Square One ...
Don't Pass GO
Don't collect $200.

Fill 'er up and take a Ride.
Do another set of figures.

 

Which way do I turn the idle screws to start running more rich?

 

Counter-clockwise.

You look like you might be close to a good Mixture so don't turn the Screw very far.
Forget fractions.
Do it in degrees.
Try the width of 2 Nickels more Rich and remember that you turned them Out about 4 degrees.
You might have to split the difference and go lean if the adjustment is too much.
Hows it Idle like that?

 

Ok, I turned it 1 full turn out, for a total of 4 turns out. It feels more powerful, and so I will run with it like this for a full tank of gas and then pull the plugs and see how they look.

As for the idle, it is still great, just had to move the big screw back ever so slightly.

 

It probably is the angle your tank is setting now causing your poor gas mileage. The fuel system is gravity feed and designed to work best in its original postion.

BTW, 4 turns out on the screws is going to be way too rich. If you were originally at 3 turns, 3.25 or less turns should be good.

 

Thanks for the response Jim, but I don't think the angle of the tank would have much to do with it for a few reasons. First, a 5 gallon tank is a 5 gallon tank, no matter if it upside down, or on it's side. Secondly, it's not gravity, or at least not when you have the petcock in the 'run' position - that's vacuum. Anyway, those are my reason for thinking it could not be the problem, but ya never know...

As for the turns with the jets you could be right, but you have to remember that I have aftermartket Harley pipes on my bike so I thought the extra might do me some good. But the only way for me to be sure is for me to run it for a while and then pull the plugs. Right now, anything will be better then what MPG I am getting lol.

Thanks guys, I will post back at the end of the week.

 

I thought I told you NOT to go a Full Turn.

"The width of 2 Nickels" ... "4 degrees"

You probably went right past where the Bike needed to be.
If is starts bogging-down on the get-go ... you went way too far!

Its a precision instrument.
A 16th of a Turn is a lot when you are close to running good!

 

The idea behind the vacuum is just to have an automatic on/off valve. It does not pump, push, or force the fuel to flow.
The petcock uses the vacuum just to open a valve that lets gravity flow the fuel to the carbs!
When the engine shuts down the vacuum is gone the valve closes.

 

Since when does a XJ550 have a 5 gallon tank?
My XJ650J has a 3.4

Food for thought- I just came back from a ride to Calico and had my best fuel run of 51.4 MPG @ avg speed of 70 MPH!