fuel mileage

[mightymounce]

Just out of curiosity how many miles do most of you get to a tank of gas.  I have an 82 750c and get about 75 miles then i have to switch to reserve, to me that doesnt seem right.

[sgtslag]

My '79 K model averaged 43 MPG, and it had a 5.5(?) gallon tank.  We could go around 140 miles before we would worry about filling up.  Cheers!

[motogrady]

I have a 79 SS, get's 52 miles a gallon.
When it starts starving for fuel, I know theres a gallon left in that 4 gallon tank,
with a good 50 miles to find fuel.
75 miles and needing reserve, something's wrong, big time.

[MarkPBG]

I have a '74 CB750k and I get around 100-115 miles before switching to reserve. So I am averring between 31 and 36MPG, mostly stop and go in town driving, and no easy launches from the lights. My riding style is NOT mileage friendly. I've got 17/48 sprocket combo on it with a mac 4 into 1 exhaust, and the thing is also jetted way too rich. I bet with some tweaks, and careful riding, I could hit 40 MPG.

So with all these things working against my mileage, I'm still getting 25-40 miles more than you before hitting reserve…..I agree, something is not right.

[LukeM]

I believe my '79 CB750 had a 3.5 gallon tank.  I was averaging between 40-45 mpg with the bike in standard tune. 4 into 4 exhaust, stock carbs, airbox/filter, factory jets and settings.

My current 700cc Shadow averages 44-50 mpg.  So I'm guessing if you're going half that range, there's something amiss.

Any dents in the gas tank that would take up space?  How many gallons when you fill up? Is it a stock tank?
Is it leaking gas anywhere? Let it idle on the center stand, and look for drips from the carbs or the overflow tubes or the fuel lines from the tank to the carb bank.
Stock carbs, or aftermarket?
Tires at a good pressure?
Any other items that would add wind resistance (fairing, BIG saddlebags, parachutes)?
Pull the plugs and inspect them for color.  If it's running rich (I'm with MarkPBG on this one), they would be a powdery black color on the insulator. You may notice a similar condition on the inside of the exhaust pipes.

This is your homework assignment for this week. Let us know if we can help more.

Luke M

[shinyribs]

My '80 F is now 823 cc's with 900 cams and carbs jetted richer to accommodate pods.Ported head and 4-1 exhaust.  All of that should require more fuel than a stock bike. And I'm getting 42-45 mpg regularly.

My cruising rpm at 70 mph is 6000 and I usually run my bike pretty hard. Meaning, I'm rarely below 6k rpm when I'm out goofing off. Actually,unless I'm in town my bike is pretty much screaming nonstop.  I usually stop for fuel at around 125-150 miles and I've only hit reserve once.

I'd agree that you're definitely using more fuel than you should.

[Re-run]

Man, that is bad. I would check your plugs and see if they are indicating a rich condition. After a few minutes, check the brake rotors for a lot of heat. It could be bad tuning but it could be parasitic drag.