Why the heck is my gas mileage so bad? 79 1000 LTD

Hey guys, my apologies in advance for the lengthy post, but I wanted to describe things as accurately as possible. Bike is a 1979 LTD 1000. I want to go on a long trip next year, but still have problems with my carb tuning and mpg. Here is what I know and don't know:

Engine should be original as per the PO. But he didn't know for sure, he was told so from his PO.
Compression at 140 lbs, all within 10%
Valves are set, while I did that checked the cams, look to be original
New plugs, ignition is the transistor type, no breakers.
Carbs are VM 26 pumpers, new gaskets, jets, needles, O-rings, pumps work
Carbs are synced, main jets 117.5, pilots 17.5, idle mixture screw 1.5 turns out
K&N pod filters, Vance and Hines 4in1
Carbs synced with 4 vacuum gauges

Here is what I observed:

• WOT: Runs pretty good, but after 60 mls or so mostly WOT in the TX Hill country, headers were really blued out and plugs looked pretty darn lean. Gas mileage was 32 mpg, which maybe isn't too bad
• Midrange: I rode another 80 or so miles at 60-70 mph, lots of turns, some hills but I took it easy. Plugs looked a tad rich to me, gas mileage was about 31 mpg
• Idle: Plugs are always sooty, I tried #15 pilots, still sooty plugs but runs like crap with those pilot

What is a reasonable gas mileage for a KZ1000 LTD?

When I rebuilt the carbs the kit came with needles that were much shorter than the needles in my carb. I got the carbs on ebay, so not sure whether they had the correct needles in there, can short needles mess things up at midrange and idle?

Can the engine suck gas through the main-jet at idle when the needle is too short and cause a rich condition at idle?

Again, sorry for the many questions, but I really hope someone can help!
Happy New Year y'all!

I installed a set of CV carbs years ago and have used them since. I could get 48-50 MPG. I don't understand the needles being shorter than stock. I would not have installed them.

Get a regular gas tank for long rides. It will slip right on. Roy

damm, I get 10 mpg......I would love to get 30

Hwy mileage depends on wind resistance. On my 750 twin, I could get 60 mpg at 60 mph and drop to 45 mpg at 70 - 75 mph.

Sounds like your carb tune is screwed up. Too rich low end, too lean high. If the mix is off center, you have to open the throttle more to make up for it so gas mileage tanks.

anotherZ wrote: When I rebuilt the carbs the kit came with needles that were much shorter than the needles in my carb. I got the carbs on ebay, so not sure whether they had the correct needles in there, can short needles mess things up at midrange and idle?!

Not at idle, but maybe at midrange. The taper rate really affects midrange.

anotherZ wrote: Can the engine suck gas through the main-jet at idle when the needle is too short and cause a rich condition at idle?
!

I don't think so unless something is keeping the piston from seating.

Thanks for all the suggestions.

Regarding the gas-tank, yes I would love to get a bigger one, however the PO had spent $1500 on a paintjob so it would suck to have to spend money again, but sooner or later I will.

I used the new "shorter" needles, because I had no way to tell whether the needles that came in my carb were the correct ones. At that point I assumed the rebuilt kit had the correct needles. Anyone know the stock needle length/taper of the VM 26 carbs?

I can't believe that people talk about 40 and above gas mileage on these old 900 and 1000's! I average about 35mpg. I think if you rode in high gear at 50 mph and never faster on the highway you might get above 40.

etbike3135 wrote: I can't believe that people talk about 40 and above gas mileage on these old 900 and 1000's! I average about 35mpg. I think if you rode in high gear at 50 mph and never faster on the highway you might get above 40.

Even My little 650 with pretty much the same, header, pods, jetted up etc was right at 35 maybe 38 tops.

They lied about the Honda 50 getting 200 miles to a gal too I ave 75 to 80 but it was wide open all the time too.

Honestly I would care much less if it was 30 or 40 if I had an original size tank. But I have planned a 2000 mls round trip and now I get 95 mls out of my 3 gal tank. That means I need to look for gas every 60 miles....

You can believe or not that these bikes get good gas mileage. Most people won't listen to advice on here and do what is suggested and then grumble. I am not talking about this thread just in general.

I don't expect this rider to go out and buy a set of CV carbs, I am just telling him what he could expect. I check my mileage everytime I fill up on every vehicle I own and I know what fuel mileage I get.

My KZ650 gets an easy 40 mpg @ 80 mph. My GPz1100 ELR gets an easy 35 mpg @ 80 mph. Neither one of these are stock bikes, both have big bore kits, bigger cams, 4 into 1 pipes and bigger carbs.
I bought my KZ650 new in 1978 and when stock I got high 40's. I really the key to getting good milage out of these is making sure they are in great running condition and they have been tuned properly.

baldy110 wrote: My KZ650 gets an easy 40 mpg @ 80 mph. My GPz1100 ELR gets an easy 35 mpg @ 80 mph. Neither one of these are stock bikes, both have big bore kits, bigger cams, 4 into 1 pipes and bigger carbs.
I bought my KZ650 new in 1978 and when stock I got high 40's. I really the key to getting good milage out of these is making sure they are in great running condition and they have been tuned properly.

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