Fuel Mixture Screw And Mileage - Kawasaki KLR 650 Forum
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post #1 of 27 Old 09-24-2013, 05:01 AM Thread Starter
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Fuel Mixture Screw And Mileage

Hey guys, got a question about the fuel mixture screw and mileage.

I ran out of gas the other day, off a full tank, at 177 miles, so I've determined on more than one occasion that I can generally go about 180 miles before I have to hit reserve. I would note that I've never computed my mileage by comparing miles ridden to gallons put in.

If internet data is accurate, there are 5.6 gallons of "usable" gas in a full tank before switching to reserve and it seems to me that 180 miles on a brim-full tank of gas is pretty shitty mileage, like in the low to mid 30's or so. Yeah, I'm big with a lot of wind resistance, but my general commuting cruising speed is around 60mph so it's not like I'm pushing things.

Anyhoo, I'm wondering if, even though the bike runs good, I have my fuel mixture screw set a little too rich and am wasting gas and subsequently hurting my fuel mileage. I also have some black soot buildup on a reflector I remounted just aft of my tail pipe.

I did the .22 Mod/Slide drill a couple of years ago and, if memory serves me correctly, I set the screw out 2-1/4 turns.

The thing starts and runs fine as far as I'm concerned, but do you guys think my mixture's too rich and I could go back to maybe just 2 turns out and save some gas?

Pardon my ignorance on such matters. Just wanted some more knowledgeable opinions before I risk breaking my choke cable connector because I'd rather just rotate the carb to do this if it would be a good idea.

And, no, I probably won't spring for one of those tools or knobs to reach the fuel mixture screw as it sits. And, yes, until I bring the thing in to strip it down this Winter, I'm too lazy to go to the trouble of taking the spark plug out right now and diagnosing it.

Any advice or thoughts would be appreciated.



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post #2 of 27 Old 09-24-2013, 08:18 AM
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The fuel screw only dominates air/fuel mixture only below 1/4 throttle; thus . . . unless you tool about with your throttle closed, that little screw isn't responsible for your lower-than-expected fuel mileage, IMHO.

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post #3 of 27 Old 09-24-2013, 09:23 AM
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Quote:
Originally Posted by Damocles View Post
The fuel screw only dominates air/fuel mixture only below 1/4 throttle; thus . . . unless you tool about with your throttle closed, that little screw isn't responsible for your lower-than-expected fuel mileage, IMHO.


+1

60 mph on my KLR is about 3/4 throttle right in needle/main jet territory. What size main jet is in the carb? How many washers under the needle? How's the plug look? Air filter clean?

My 08 has the stock main, 2 washers under the needle and gets 50 mpg consistently.

No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him. 1 Cor 2:9
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post #4 of 27 Old 09-24-2013, 01:43 PM
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I don't track the numbers either, brother. The soot would make me wonder, too. FWIW, though, I get gas when I hit 190 miles. If not, I hit reserve. Been like that since the day I got it, pre and post installation of a bigger jet, KLX, airbox mods, etc. I like to vroom vroom, though.

Air filter could be a good call. I forgot about mine for a WHILE and it definitely improved things when my brain kicked back in and dealt with it. If that's it, that's about as easy a solution as you got, too. Good luck.




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post #5 of 27 Old 09-24-2013, 04:21 PM Thread Starter
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Thanks, guys. Air filter's pretty clean (cleaned it about a month ago and have only been on pavement since), main jet is whatever came in it when it was new and I have 2 washers under the needle. I'm too lazy to look at the plug and I'll probably be replacing it this Winter since it will have about 15K on it by then.

Doesn't just 180 miles before running out of gas seem kind of extreme? I guess my next step should be to actually compute my mileage by comparing how many miles I rode to how much gas it actually takes to fill it up. I really can't tell how much gas is left in the tank when I run out, but I definitely have to switch it to reserve to get it to start and run again, so it's gotta be pretty empty.

Unfortunately, when it happened this time, I didn't have enough $ on me to completely fill up the tank to do the mileage check.

I'll rule out the fuel mixture screw and leave it where it is since I'm content with the way it runs.

Even though I've been good about maintaining it, that stock air filter is 4 years old now. Maybe I should think about picking up a new one? Even though I've cleaned it routinely, I suppose you never get it truly clean and over time it doesn't flow as well as it should.



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post #6 of 27 Old 09-24-2013, 06:00 PM
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A modest proposal: Do a PRECISE mileage check, planalp, for a better look at the magnitude of your problem, if any!

Calculate your miles-per-gallon in your normal spectrum of riding.

Regardless, doubt your air cleaner's the culprit (if there be a culprit).
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post #7 of 27 Old 09-24-2013, 06:15 PM
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Be aware also that the pickup tube length attached to the fuel valve is said to vary in the KLR's. So when you have to switch to reserve you don't really know whether there is a half gallon, a whole gallon, or more left in the tank.

I ran mine once to complete empty. I made around 50 miles on reserve before it died. So for me a bit more than a gallon left in reserve.

Gray-haired riders donít get that way from pure luck.

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post #8 of 27 Old 09-24-2013, 06:46 PM
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Be aware also that the pickup tube length attached to the fuel valve is said to vary in the KLR's.
+ 1; thus, I thought an absolute miles-per-gallon calculation might be useful.
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post #9 of 27 Old 09-24-2013, 07:29 PM
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Agreed. I basically hit reserve around 190, but when I fill up (to the brim) it is only a little over four gallons. Kawasaki is not big on precision.




"In a car you're always in a compartment, and because you're used to it you don't realize that through that car window everything you see is just more TV." R. Pirsig

PPMC #1.
Soon, we ride.

AKA JD Mader or you can call me "Dan" just not early for dinner.

Click my handle for a link to my homepage/blog...which has nothing to do with MCs. Free literature and music! Viva La Revolucion!
-------------------
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post #10 of 27 Old 09-24-2013, 08:02 PM Thread Starter
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Interesting about the tube length, flash. I didn't know that.

I agree with Damocles: really no point in harping on it until I can do an accurate mileage check to see exactly what my mileage per gallon actually is.

I appreciate the input.



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