28 mpg

[jjz28]

When my vacuum advance was unhooked, my bike didnt run good at all. It was harder to pull out (needed more throttle) and just didnt run right. Seems like if it wasnt working, you would know unless it never did. And maybe thats just my bike.

[crazy steve]

28mpg doesn't seem unreasonable to me... especially since you are talking a US gallon, presumably? They are smaller than the imperial ones we use here. That's for an old, heavy bike and a pillion. Add a few hills, a bit of speed, maybe a headwind....

I'm with CBug, that's low. I have seen mileage that low on my '78, but that was beating the snot out of it. Under more 'normal' conditions, mine typically got mid 30s. I've never seen over 40.... and that takes restraint with your throttle hand....

[MaximPhil]

Too slow maybe these biks like to go fast I always get better mileage on the slab going 80 mph

Hi GarthXS,
I hope you are right as i have 100 of miles of slab to run to Iron Horse. I am even installing aux lights as slowing down is not an option and i like to see what I am going to hit next
Phil

[James England]

and that takes restraint with your throttle hand....

Which leads me to wonder.... what's the point in riding an 1100cc bike if fuel economy is of such concern? I can't imagine anything more frustrating than restraining one's throttle hand all the time in order to eke out maximum mpg on a wopping bike, old school engine developed when fuel economy was the last thing on any manufacturer's design sheet. XS1100, CBX1000, Z1300 etc .... The Suzuki 750 'kettle' 2-stroke did about 25mpg. My Yamaha RD400 about the same. Nobody talked about fuel economy when they were made and it really wasn't high on the list of design priorities. Mega-power and speed were high up there though.

Riding normally on any XS1100 I've ever had, I've never had more than 35mpg... if that. On my brand-new one, at 100mph steady speed, I could actually see the fuel gauge needle moving inexorably to the left!

If fuel economy is of paramount importance, then then a late 1970's bike from the last millenium really isn't where it's at, IMO. I'd just ride the bike and not watch the fuel gauge.... or buy a 500cc modern bike.......

[BA80]

28 is about what I get when I'm running 80 - 90 MPH. I normally get 35 -38 and even better if I keep the tach at or under 4K. (about 60- 65MPH with the 850FD).

Is your air filter clean? If there's no restriction, like dirty air filter, you might try dropping your float level 1mm or so and see how it does.

[geobiker]

A little low

I get about mid 30's if I'm not honking on it too hard. Ethanol blended gas, sold on the east coast, will not give as good of mileage as non ethanol blended gasoline.

You mentioned that the bike starts right-up when its cold which, for whatever the reason, the bike is running on the rich side. If it is not a timing advance issue, or a float issue, it could be a problem with the needle jets (emulsion tubes) in your carbs. My bike had a similar problem and by going to the same needle jets in all four carbs, the problem was solved.

Another possible thing that will degrade mileage, which I don't believe I have seen mentioned, is that if you brakes drag this will reduce mileage.

In the end, in the grand scheme 28 mpg is not significanty different that 33 or 34 mpg, unless your doing a lot of miles in a year. These old bikes will never get the mileage that modern fuel injected bikes get!

[MaximPhil]

Which leads me to wonder.... what's the point in riding an 1100cc bike if fuel economy is of such concern? I can't imagine anything more frustrating than restraining one's throttle hand all the time in order to eke out maximum mpg on a wopping bike, old school engine developed when fuel economy was the last thing on any manufacturer's design sheet. XS1100, CBX1000, Z1300 etc .... The Suzuki 750 'kettle' 2-stroke did about 25mpg. My Yamaha RD400 about the same. Nobody talked about fuel economy when they were made and it really wasn't high on the list of design priorities. Mega-power and speed were high up there though.

Riding normally on any XS1100 I've ever had, I've never had more than 35mpg... if that. On my brand-new one, at 100mph steady speed, I could actually see the fuel gauge needle moving inexorably to the left!

If fuel economy is of paramount importance, then then a late 1970's bike from the last millenium really isn't where it's at, IMO. I'd just ride the bike and not watch the fuel gauge.... or buy a 500cc modern bike.......

Hi James,
At 100mph please watch the road. Never mind the damn gauges
Phil

[DGXSER]

Honestly, for me, I find I get my better milage when I ride it long distances. Start it ride 10-20 miles park it, go again a coupel days later...I end up in the low 30s on milage.

No joke, my ride Saturday was everybit the constant twisting, turning, hills we saw in Cambridge. No time to stop and ponder the world in your head or you would careen off into a cow or field of tobacco. I barely had a moment I was not on the throttle or gearing down two changes to bring her down for the impending curves. So, I was certainly not going a constant speed, or taking it easy on the throttle. And got 41-42 MPG, and yes, that is a US Gallon.

James, there is a difference between worrying about fuel economy and trying to optimize it than paying attention to the signals your bike is not runnign correctly when your MPG goes way south. For instance, I took a trip with another local XSive a couple years ago, we fueld up together before heading out. All highway miles, 56 miles in he runs out of gas. Now, should we just say "oh well, that is the way of a sport bike"? He had adjusted his plug gap to overcome a carb issue, he corrected it when we got to the destination another 40 miles later. We filled up before leaving to head back, he got home on one tank. So MPG can give you input to your engines needs.

[jetmechmarty]

Your float height may be too high, only thing I can think of. Not sure about the spec. you mentioned above. What does that translate into using a float height measurement with the carbs upside down on the bench?

Phil, I used the FSM spec. I don't remember the numer off hand. I did a lot of checking because I was concerned about old fuel saturated floats not functioning properly.

Maybe your timing chain is worn out. When was the last time it was changed?

Yard Dogg, My timing chain is new this spring.

[DGXSER]

Marty, have you checked your plug gaps, or ohmed your coils lately? Just a thought, I know your a pretty maticulous guy so you probably have them set within a babies hair of dead flat spec.

[jetmechmarty]

Which leads me to wonder.... what's the point in riding an 1100cc bike if fuel economy is of such concern? I can't imagine anything more frustrating than restraining one's throttle hand all the time in order to eke out maximum mpg on a wopping bike, old school engine developed when fuel economy was the last thing on any manufacturer's design sheet. XS1100, CBX1000, Z1300 etc .... The Suzuki 750 'kettle' 2-stroke did about 25mpg. My Yamaha RD400 about the same. Nobody talked about fuel economy when they were made and it really wasn't high on the list of design priorities. Mega-power and speed were high up there though.

Riding normally on any XS1100 I've ever had, I've never had more than 35mpg... if that. On my brand-new one, at 100mph steady speed, I could actually see the fuel gauge needle moving inexorably to the left!

If fuel economy is of paramount importance, then then a late 1970's bike from the last millenium really isn't where it's at, IMO. I'd just ride the bike and not watch the fuel gauge.... or buy a 500cc modern bike.......

James,

This is about getting my bike running right. My mileage is poor enough that I suspect something is wrong. I go with Bug, Steve, and Greg, believing I should be getting around 35 mpg unless I'm thrashing it.

My air filter was cleaned in the spring. My brakes were rebuilt over the winter, there is no drag. Wheel bearings were replaced as well. I'm running 45 psi in the rear tire and 40 psi in the front.

At my next opportunity, I'll check the timing and vacuum advance.

[jetmechmarty]

Marty, have you checked your plug gaps, or ohmed your coils lately? Just a thought, I know your a pretty maticulous guy so you probably have them set within a babies hair of dead flat spec.

Nope, I haven't done it. The coils are original. I just bought a SG for parts that has new Accel coils and wires on it. I plan to do the swap after I work through this and/or the weather turns cold. I suffered some missing in the rain on Saturday, so that's an issue as well. I love old motorcycles!

[James England]

James, there is a difference between worrying about fuel economy and trying to optimize it than paying attention to the signals your bike is not running correctly when your MPG goes way south.

Yes, I agree entirely. I didn't mean just ignore it (although, re-reading my post, it does look that way!). Yes, optimum performance is absolutely what one needs. What I really meant was the "gotta watch my throttle hand" philosophy all the time.... Riding a bike like the XS1100 is a bit like eggs and omelettes.... you have to break a few to make one....you have to use fuel to keep the 1100 running and it's never been 'good' on fuel even when new.

But, yes, a bike running at its best is my philosophy too and the source of a lot of pleasure, knowing that everything is just-so.

[James England]

This is about getting my bike running right. I should be getting around 35 mpg unless I'm thrashing it.

Agreed, as per my previous post. But...honestly, I think 35mpg on a US gallon is a bit much to expect. I've read the posts here and looked at the mpg poll etc and I just don't see how anyone gets 35mpg+ on one UK gallon, let alone a US one. I've had four XS1100's (running ones, that is) and even my new one didn't get that. My last one, low mileage, iridium plugs, Dyna coils, new/restored everything, mint looking etc etc didn't either. I might have to get my right wrist X-rayed....

[DGXSER]

Agreed, as per my previous post. But...honestly, I think 35mpg on a US gallon is a bit much to expect. I've read the posts here and looked at the mpg poll etc and I just don't see how anyone gets 35mpg+ on one UK gallon, let alone a US one. I've had four XS1100's (running ones, that is) and even my new one didn't get that. My last one, low mileage, iridium plugs, Dyna coils, new/restored everything, mint looking etc etc didn't either. I might have to get my right wrist X-rayed....

James, I think you need to tell your neighbors to quit syphoning your petrol out the bike for thier mowers.