Fuel capacity & range

[Danian]

I'm pretty sure the tank gauge on my CB700SC can't be completely trusted, so I wanted to get some input from you guys.

The book says we've got like a 4 gallon capacity, .5 of that reserve.  However, I fill up when I hit the red and only put in about 2.5 gallons.  I hit the red at around 90-100 miles and need to switch to reserve definitely at around 110 miles.  (Only had to do that once.  I don't like taking it down that low.)

Does this sound about right to you guys?

I'm not usually an aggressive rider and my best mileage is, of course, when it's distance highway riding at 75mph.  If I can squeeze out more mileage, let me know how I can do that.

[Brittles]

You shouldn't be needing to switch to reserve at 110 miles unless your getting poor mpg. It sounds like your getting around 40 mpg which isn't too bad. I get around 45 mpg for reference. When you say you definetely had to switch to reserve at 110 miles do you mean the engine was actually starving for fuel?

[hppants]

FWIW, I get an honest 46 mpg when I'm riding easy (60ish mph in the backcountry), and as low as 38 mpg when I'm riding hard.  It's more fun to get 38 mpg, though... 

[lew750]

I'm pretty sure the tank gauge on my CB700SC can't be completely trusted, so I wanted to get some input from you guys.

The book says we've got like a 4 gallon capacity, .5 of that reserve.  However, I fill up when I hit the red and only put in about 2.5 gallons.  I hit the red at around 90-100 miles and need to switch to reserve definitely at around 110 miles.  (Only had to do that once.  I don't like taking it down that low.)

Does this sound about right to you guys?

I'm not usually an aggressive rider and my best mileage is, of course, when it's distance highway riding at 75mph.  If I can squeeze out more mileage, let me know how I can do that.

From your description, you seem to be getting 45-50 mpg and have just under 2 gallons left when you hit reserve.  You can probably get 180-200 miles per tank if you don't mind riding another 70 miles on reserve.

I would check the fuel tank and petcock assembly.  You'll probably find the answer to your inaccurate gauge at the same time.

[lew750]

Of course, you know I was kidding about the 70 miles on reserve, don't you?

[windrider]

Math lesson time.  You have 4 gallons, 3.5 usable, and .5 for Reserve, according to your first post.  You rode 110 miles and had to hit reserve.  That would be 110 miles divide by 3.5 gallons of fuel.  That would give you 31.2 miles per gallon, a little low in my opinion.  Now did you hit reserve because you ran out of gas?  The best thing to do is fill your tank and look at where you fill it to.  Reset the trip meter, or write down the mileage on the odometer.  Go for a ride of 50 miles or so, making sure you take an expressway run and compare the odometer miles with the mile markers.  This is best done over a 10 mile stretch, note the mileage with the tenths digit at mile one, and again at mile 10.
Return to the same station, and the same pump, parked the same way, and fill up.  Get your total miles traveled, (ending odometer subtracted from starting odometer), and divide that by gallons and tenths of gas used.  This will give you your fuel mileage.  Anything else is a guess or estimation!  To be extremely accurate, you need to calculate your odometer error based on the mile markers and and what your odometer read during that 10 mile stretch.  Each tenth of a mile off equals one percent, in other words, if you were 3 tenths more miles read than traveled, then you need to subtract 3 percent from miles traveled.  If you were 6 tenths less miles read than traveled, then you need to add 6 percent to your total miles traveled.  Do this before you divide by fuel used.  

If you switched to reserve because you got scared you would run out somewhere based on what the gauge said, forget it.  Fill up and reset the trip meter, ride until it runs out, then switch to reserve.  You should still have 15 miles left, even at 30 miles per gallon.  If you're on the highway when it runs out, you should be able to switch it, without loosing more than 20 mph.  Practice this maneuver occasionally, it may save you one day.  Hope this helps.

[Brittles]

No, math lesson is he rode 90 to 100 miles and put in 2.5 gallons of gas = right around 40 mpg.

Honda lists the fuel capacity on the 700s as 4.2 gallons. That doesn't mean you can run totally out of gas and it will take 4.2 gallons to refill. There's always some fuel left in the tank that can't be burned. Plus, I wonder if the capacities aren't measured with the tank brimming full, which is not practical.

You can get more miles out of a tank, when it gets real low, by tilting the bike as far left as possible to get the gas that's on the right side of the tank tunnel to the left, petcock side.

[Danian]

Okay, according to the book, the fuel capacity is 4.2 US gal and the fuel reserve capacity is 2.6 US gal.  Is the 2.6 gal included in the 4.2 gal fuel capacity?  Because if so, that means you would go through 1.6 gallons before before having to go to reserves.  That doesn't make much sense.  So is it 4.2 gallons and THEN 2.6 gallons of reserve?  Like I said, I hit the red and fill up, it's usually 2.5 gallons at around 100 miles, give or take 5 miles.  Confusing...

I calculate my MPG every time I fill up based on the mileage and fuel used.  I'm usually in the high 30's.  When I say I have to hit the reserves, I mean the engine loses power and sputters out when opening the throttle.  I've never run the reserve out, so I honestly don't know how long it'll last.  I was just wondering how everyone else was doing.

At one point, I thought I needed to do a petcock rebuild.  If I put the bike on the side stand overnight, the bike is very hard to start the next morning.  It acts as though the engine was flooded.  I almost always put it on the center stand for that reason.  Perhaps there IS something wrong with the petcock and a rebuild will not only solve that problem, but boost up the MPG as well?

[Brittles]

The reserve is 2.6 QUARTS. This is included in the 4.2 gallon capacity.

Maybe your not filling your tank all the way? While you certainly don't want to fill it to the top edge of the filler hole, you might be missing out on some capacity. Best to underfill than overfill though as we all know an overfill can get messy.

Would be interesting to see how far the bike would go on reserve. I've used those quart size camping fuel bottles filled with gas to test how far a bike would really go on reserve (I haven't done it on my NH yet). Just need to make sure your not too far from a gas station when you totally run out as that quart isn't going to take you far.

[windrider]

Your original post states that the tank is 4.2 gallons with .5 gallon reserve.  Last post states 4.2 gallons with 2.6 gallon reserve.  I doubt the latter is true as this would be more reserve than main.  Whatever the book says for total fuel will include reserve.  Now do this.  Get an empty 5 gallon gas can, and a 3 foot long piece of fuel line the size to fit to the petcock.  Go fill the bike and come straight home.  Disconnect fuel line at petcock, connect long fuel line, put it in to empty can, and turn on petcock and walk away. (I hope you don't have a vacuum petcock). When the fuel quits running, look in can and see how much fuel you have.  Also turn on the switch and check the fuel gauge, so you'll know what it says when the main runs out.  Now put it on reserve, and walk away again.  When it quits running, look in the can again.  This time it should be close to full.  If not, you have a different tank, damaged tank, petcock problem.  Also in last post, you said you hit reserve because bike started starving.  Doesn't sound like it's really running out of fuel.  If it runs out of fuel, it usually dies, period.  It's a process of elimination, and doing test to you find what may be wrong.

[hppants]

FWIW, if I was looking to get more accurate than the odometer, I would not use the tenth mile markers.  Let's face it, that's a WAG at best.  I'd probably go with the GPS.  Technically, even that has some error, but I've made my point.

If you are getting low 30's for fuel mileage, unless you are running the bike race hard, I pull and check the plugs to see if you are running too rich.  I've heard other NHF members mention hard to start on the side stand issues.  My bike does not have this problem and I'm not sure why others do.

[Danian]

   D'oh!  You're right!  It's 2.6 QUARTS!  I can't believe I misread that!

I'll guess I'll do a couple of extended runs on it and monitor the MPG, maybe throw some Sea Foam through it.  Probably tune it up, as well.  Then see where I stand.

I just wanted to see what other people were getting.  Sounds like most people are in the 40-50 mpg range and I know I'm definitely not getting that.

[pryan67]

Just checked my mileage on my 92 750 NH....

4.22 gallons is what it took to fill up...

144 miles from last fill up...

that's only 34 MPG...

granted, it's been cold here, so I tend to let it idle to warm up...but that still sounds REALLY low...

I'll see what happens now that it's getting warmer here

[hap]

If it makes you feel any better, I get under 40mpg. Different bike than yours, but the consensus is it's below average. But hey, I only get 17 in my truck, so 39 sound great to me.

[FocusPlayer]

99 750 NH  -  I got 44 mph last tank

[pryan67]

seems like I need a tune up :) don't wanna do that myself (plugs, no problem...wires...easy...the carbs themselves...not a chance)

don't really want to dump a few hundred into the bike though

[hap]

pryan, try dumping some Seafoam in your gas tank for them carbs. Read the instructions on the can for amount per gallon and don't over do it. If one is good two is "not" better. I use for all my equipment and only about three time a year for the NH. You can buy it at most auto parts stores ans Wally's World carries it also.

[pryan67]

Thanks...I'll try that

[SliverXZennon]

Yesterday I filled up at 118 miles and the needle was in the reserve red. I did ONLY put 2.8 gallons in the tank though!

I got 41mpg and that's the first tank out of winter storage.

Is there a way to adjust the gauge? It seems like it's way off. I realize I could do the run out of gas thing but I'd much rather not...

[ariwhiteboy]

I'm gettin about 40 mpg with the CB1000...not too shabby

[rider84]

new to the forum,love it ive got a 1984 700s with 46ooo on it.i get about 170miles before i hit reserve.thats running highway at 65to70 miles an hour.never ran it out?

[pw363]

i used to have an 84 700s and consistantly got 48-50 mpg and once got 55.5 on a joy ride with a conservative riding buddy. i check every tank for mpg on every bike i own. last tank on my 93 750 that i'm using to commute to work 62 miles per day was exactly 50 mpg. and i consistantly get 40-42 from my cbr1100xx which has about 100 more horsepower. i think you need a tune-up.

[FireCpt]

Hi everyone!
I'm not only new to the forum, but a new cycle rider also. I have never owned a motorcycle before I bought my 1992 CB 750 NH. I have owned it for 2 years, and still consider myself a novice rider. On the advice of my brother, a rider for 30+ years,I ran my very first tank of gas out completely (except of course for the reserve) just to see how many miles I get per tank (I have no gas gauge). I got 209 miles, which equals about 50 MPG. I now tank up at 200 miles.

Of course, you have to take into account that I ride like a little old lady compared to most of the people I know  . 22 years of responding to accidents will make you awfully careful!

I look forward to participating in these forums...

FireCpt

[hppants]

Welcome Firecapt.  Your fuel mileage is excellent.  My brother's a fireman/paramedic.  You guys are a special bunch no doubt, but thank heavens for you.  I did a 160 training class on HAZMAT emergency response (for emergency managers) and we dressed out several times.  I'll stick to my desk job, thank you very much.

See that you are in Atlanta - have you heard about our Nighthawk rally planned for May 21-23?  If you can make it, we would love to have you.

Cheers.

[muttstang]

when I had my VT500, it would actually get better gas mileage in town then on the superslab.  I think with my 250 lb frame it kind of got hurt by wind resistance going over 60 mph