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!

 

Sorry Rick, I did it before you posted back. I will turn them back and then the 4*.

Nick, you are correct, but I still don't see how it would play a factor with my fuel mileage. My fuel line is clear and it is full of fuel till the tank runs dry so that to me suggests that the carbs are getting fuel fine.

PGDBUD, I don't like you right now with your 51MPG :lol:

I don't know if its a 5 gallon tank, I just said I believe it to be that but I have no idea, if it is around 3.4 - which sounds better, that means my MPG is 22 which is still awful lol.

I'll turn down the screws and run it, see how my MPG is after that.

Thanks for the help guys!

 

Ok guys, I finally got around to getting to the air filter. The bottom half was wet with gas! As I've said before,"I'm not Tim Taylor". What does this mean and how can I correct the problem? Thanks for the help guys.

 

@ Anthony you said

So are assuming the, amount of fuel used at reserve?
You also said

".
You should fill your tank to the top and note the current milage.
When you switch to reserve, fill up to the top again, note the mileage.
Total miles traveled divided by the fuel you just put in will give you an accurate MPG reading.

@ wesley the float or floats have stuck open filling the bowl running back out the intake into the air box.

 

Wesley, check the crankcase for gasoline smell, if you have a hint of gasoline, change the oil and filter too.

 

How fast should I notice a change in the plugs color?

I have driven about 50km with the idle screws turned out the amount Rick suggested and pulled the plugs. They are only slightly changed in color - will this change be more apparent after some more riding? Or do I need to turn out the screws more?

 

Make sure you read The Hound's instructions for checking your mileage. Trying to guess at how much you've used by the time you get to reserve is useless. Top off. Note odo reading. Ride. Top off again. Note odo reading again. Subtract first odo from second and divide that number by the number of gallons of the second fill-up. Repeat and average for a true picture of your mileage.

 

Ok, I pulled the plugs and they all are looking a little dirtier. Each different from each other. Should I adjust the idle screws more? Or still drive and see if the color continues to change?

So far I have done about 100km and have about 1/2 a tank of fuel left.

 

Adjust the Screws until you SEE a difference. If you are too Rich, don't Road Test ... you might foul plugs and get stranded away from the house.

NOW< you have to put your ear into it.
Let it idle.
Crack the throttles open and LISTEN to the Exhaust Note.
Does it pick-up seamlessly or is there a wait?
What's the exhaust sound like at 2,500 rpm.
Steady ... or, "Poppity, poppity, pop-pop, poppity"???
Tune-out the Poppity.
Find the Screw that's still too Rich and Tweak***

Tweak = Barely turn the Pilot Screw. Nudge it a little tiny bit. Put the FINE in "Fine-Tuning" ... Move it and LISTEN.

Lean the Mixtures out until the Idle is strong and steady.
Make the Bike respond to Throttles with a seamless acceleration.
Immediate.
No delay.

Observing all safety precautions for COOLING and VENTILATION ...
Do a workstand Plug Chop.
Run the Bike up to 6~65 hundred and KILL it.
Read the Plugs.

Oil problems and too Rich will be evident.
Adjust EACH Hole independently. As needed.
If you can't see a difference ... clean the Plugs and try again.

EVENTUALLY ... you will get a read on each hole.
When the Bike is ready for Road Testing ... take it to where you can LOOP.
Set-up a little station and ride the loop.
Do the Plug Chop at W-O-T and kill it coasting to your tuning station.

Read those Plugs.
Adjust ONLY if there is evidence to have you do so.

Too CLEAN ... add some Richness --> TWEAK it! FINE Tune it!
Too Dark ... you know the drill ... Lean it some. Tweak it.

There's only four Plugs and the process goes pretty quickly if you are organized with gloves to handle hot Plugs and Tools organized for Pit Stopping.

 

Ok, I adjusted the screws ever so slightly in the appropriate direction and will pull them again later and see what if any other turns are required.

 

Ok, here are some pics...





Left to right - cylinder 1-4.

Let me know what needs to be done (these are the plugs with about 50km since their last adjustment. I am also getting a slight "poppity" sound from the exhaust. Very faint.

Note, plug 4 is black like that on the threads because that was the hole that was heli-coiled and I made the hole a tiny bit too big, so the plug has a little wobble going into the cylinder until the very last threads.

 

#3 is about right on. You're not using "anti sieze" on your threads.
Turn #1 out 15 * Turn 2 & 4 in 30 * Re-test re-post
Try a bunch of anti sieze on #4.

 

Ok, I adjusted the plugs to what you said, and was letting it idle a little bit. The popping got even fainter.

One interesting thing though, I touched all the exhaust pipes and #1 was much cooler then the rest - would does this mean? (I know I have to change the spark plug lead cap, was told it was bad, but I have not got around to it yet).

Could inconsistent firing be the cause of this problem = when I let off the throttle the bike almost wants to come to a complete stop by it's self instead of just coasting, could that be because the cylinder stop firing?

 

As Rick Co says " learn to tune each carb separately"
So try to find where #1 goes rich, then back off a bit.
Find where #4 goes lean, then go a bit richer.
As if you are tuning 4 separate motors.
Also, you have to get #4 to seal-up somehow.

 

I want a colortune! lol

Ok, I will continue 'playing' with the screws...

 

Btw, can anyone sat for certain if the different tank placement could be causing the petcock to not 'touch' fuel and thus forcing me to think that it is running out but really the angle of the tank has caused the petcock to be unable to draw in fuel.

 

You can bench test the flow of your tank at different angles, and different amounts of gas in it, by mouth suction on a long clear hose attached to petcock vacuum hose.
You could empty the tank, and see how much gas it holds before reserve flows, then switch to "ON", and fill until it flows again.
Measure the gas using empty oil bottles.

 

Ok, I think I might have solved the problem. I had to remove the petcock filter and make up my own intake that was a little lower.

So now, if anyone is interested, I have my petcock filter for sale. Just make a offer, its in perfect condition.

 

when your low on gas fill up at a gas station and actually look at the pump to see how much gas you put in, your tank is about that size

 

What you wanna do is go fill up your gas tank and reset the trip odometer... drive it around for 100 miles or so or until you need gas... grab a calculator or a cell phone may have one. go fill up with gas and look and see how much you actually put in. take that number... let's say it's 3.432 gallons... and the miles/KM you drove... lets say it was 124 miles... take the miles and divide by gallons.... 124 / 3.432 = in this case is 36.13MPG (I just made up these numbers)... I do this all the time with my cars and trucks, don't really worry about it on the bike but i am tempted to see what i do get for MPG...

So to wrap up MILES(Driven between fill-ups) divided by GALLONS (amount used at second fill-up)