Bonneville America Forums Forums Technical Forums General Tech Low MPG ... what am I doing wrong?

OK, this feels like a dumb question, but I'll ask anyway ...

I see posts from a number of people claiming 50MPG or higher. I've got a stock '07 SM with the AI removed and no other mods. What am I doing wrong that leads to (usually) less than 40MPG?

The starter bike I traded up from was a Honda Shadow 600 ... admittedly a much smaller bike, but I was used to getting close to 60MPG on that, and dropping 20MPG is a bit more than I expected in the switch to the Speedy.

I'm not a speed freak ... no extended cruising at high speeds or high RPMs, no really fast starts from a stop. I do a lot of in-city riding (probably 75/25 local/highway), and I tend to cruise at between 3500 and 4000 RPM when I'm not accelerating or decelerating.

Do I need to change something about the way I drive? Do I need to make some kind of change to the stock bike? Or do I just have unrealistic expectations?


Thanks,
--Brandon

Reality check:
Have a look at the posts where you see the 50 MPG and look at the rider location. maybe they're british (bigger gallon). My stock TBA does 48 miles per us gallon under good highway conditions.

You could try having your carbs synced.

Mid-40s is a realistic number.

I consistently get mid 40s on either my America or Bonneville (both 790s) with a mix of town and country driving and (guessing here, no tach) cruising at 3500 to 4000 rpm. I had been getting 50-55mpg with my Honda 750 but I attribute that to lower rpm and less fun had while riding

45 mpg average with my tba here.....

How many miles do have on it.It seams to me that I got better milage after the first couple of tank fulls(break in period?)I got mid to upper 40s half of the time with my wife on the back.Have not checked since I made the air box and jet changes

I had the same problem. My mistake was starting to do mods before I had some miles on it. I was down to 25 mpg. I started reversing my mods and around 1200 miles my mileage stared getting better.....much better. Check my sig and see what mods I have now and I am getting consistantky mid 40's. Give it some time and miles.

It's all in the wrist. I get 25-30mpg on my '03 Speedy, but I ride hard. The more you spend at WFO, the lower your mpg.

How much do you weigh? I tend to get 35-42mpg on long trips, depending on head/tail winds (whether my fat carcass is acting as a parachute or a sail, hindering or helping). I think the worst gas mileage I got was high 20's, running from Great Falls to Helena at 90+ mph with a head wind. Needless to say I don't do that very often.

One thing I noticed in California (and I'll start a fresh thread about this soon) is that I seemed to get much better gas mileage closer to sea level, and I was much more neanderthal with the throttle in traffic down there. So maybe my jetting needs to be further tweaked.

First, check again when you have more miles on the bike. Triumphs are just getting run in good at about the same mileage that imports from the other direction are all used up.
As was mentioned, the carbs could be out of sync or just in need of adjusting.
It would also probably help to change to a less restrictive exhaust system and pop out the rubber bits in the airbox. The more power the engine expends sucking in air and forcing it back out again, the more gas it eats.
One of the tricks that Chrysler used in the old Mobilgas economy runs was to get through the gears as quickly as possible. As soon as the bike will pull well enough in the next gear up, shift.
I don't know how many miles to the gallon I would have gotten with my bike stock because I started changing things as soon as I got home but, as it is now, I usually get mid to upper 40's. Best ever was 53. And, that is statute miles per US gallon.

My 04 with 9600 miles averages 42 to 43 mtg.

When stock, I too was getting low to mid 40s for MPG. If you wish to raise the MPG performance on a stock bike, I believe you'll need to let it breath better than what the factory spec'd. The stock pipes are a major problem in the breathing process, although the quiet of a stock pipe is a great thing on long trips.

Anywho,

I run a year 2005 865 cc Speedmaster and get a nearly constant 50 US MPG on a 10% Ethanol blend of 89 octane gas. Odometer reads 19K. I weigh 250 US lbs, and carry 25 lbs of saddle bag tools & flotsam.

Mods:

Stock pipes gutted to 1 & 1/2 baffles

130 jets

Uni filter with drilled out airbox

Drilled slides

Stock needles

With one hardware store washer for a shim, I ran what one dyno software writer calls 'perfect' which I believe they peg at 13.6 : 1 Air to Fuel ratio. With the above mods & 1 shim, I was running low 40s for MPG.

Since the theoretical optimum Air to Fuel ratio is closer to 14.x : 1, I figure it was safe to lose the 1 shim. It's cooler Autumn New England weather time here, and I ride all Winter when the roads are dry, so running a might leaner as a result of pulling the shim shouldn't (hopefully) equate to any discernible loss of engine life with the colder air and all. With the shim gone, I run a very consistent 50 MPG, (that's with zero high speed 90 MPH type slab miles.) At $3.20 US per gallon for 89 octane fuel, I'm OK with 50 MPG. I expect I'm real close to factory torque & horsepower numbers right there.

If I want to turn it up, some 160 mains and a coupla shims and 40 lbs in the rear tire will push me up to 67 or 68 HP / 30 - 35 MPG. Since I have no income at the moment, and the bike is my primary ride, I'll go with the high MPGs for now. No biggie ... ;-}

Check your tire pressure. Seems very simple, but soft tires will change your mpg.

Thanks for all the replies!

Looks like the first recommendation is to adjust my expectations. If I'm getting around 40MPG, it's not outside the range that other folks are getting ... perhaps on the low side of average, but not a surprising number. And it may improve a bit more with time and miles.

The recommendations that don't require mods are to make sure I maintain good tire pressure (I do that already) and to ride at lower RPMs when possible. I'll try to do that and see what kind of improvement I get.

And the last recommendation is to give it some air. I've been thinking about pulling out the snorkel, switching to a UNI filter, and knocking out a couple of baffles (along with the required rejetting), but I didn't want to do any of that just for performance or sound ... hey I was riding a 600 before, this baby's got plenty of power for me at the moment :-) ... but with you guys telling me that these mods could give me a bit better fuel economy, I'll be giving those mods some more thought after all (just what I needed, a better excuse).

Thanks again everybody.

Brandon, I consistantly get over 50 mpg. Most of the time 53 or 54. I live out in the country. Small town riding. 18 tooth front sprocket on my 05 america. Mostly 55 miles per hour. Hardly ever over 60. I would imagine that on a city driving tankfull I wouldn't expect over 42 either. I don't think that you're too far off. I wouldn't start throwing zillions of dollars into it. Might not be anything wrong.

jerry

I get 52mpg on the highway below 80mph.. over that it drops considerably. D&D's desnorkled, K&N

I get 42 mpg whether I give 'er heck or baby it...highway or city...beats driving an SUV...if you are really worried about it trade your bike in for a scooter...face it a few miles per gallon when you are getting 40 doesn't have near the impact that a few miles per gallon have when your down in the teens

I switched to a UNI filter, pulled the snorkle, drilled two baffles out, and moved to 125 mains. It's a little bit louder than I had planned on, but it still gets drowned out whenever a Harley passes, and I rode 110 miles today on right around 2 gallons. Those are highway miles, not city miles, but so far so good ... that represents about a 20% increase over my highway MPG from two weeks back.

Thanks for the suggestions everyone.

To give you an idea how much effect acceleration and gearing have on fuel economy, I've been playing with the economy guage on my gas burning truck. Holding 55 MPH on a back road near home, it says I'm getting up to 43 MPG. Accelerating lightly from a stopsign, it drops to around 5 and jumps to 10 when it shifts.

I only get 40 mph, but I weigh 300+. I desnorkled and cut out two baffles on the pipes.

Possibly the easiest thing to experiment with is your riding style. By the sounds of it, you're taking it *too* easy!! Fill the tank up, reset the trip meter then ride her a bit harder. Take it to 5k in each gear before changing and then cruise in a gear lower than usual (4500revs). Do this for a tankful and see if anything changes. Then report back here!!

I would be curious too. I do find myself cruising along 3000-3500 rpm quite a bit. I never run below 3000 and most of the time shift 4000-4500 rpms when accelerating. Could holding a slightly higher rpm result in higher mileage? Interesting. I normally get anywhere from 35 mpg (all town traffic) to 45 mpg (all hwy.).

I don't have the tach yet, so I can't comment on my RPM's, but I got 46MPG last fill up.

- 07 TBA with ~400 miles on it.
- Riding around Colorado Springs, 0% highway
- About 6000' - 6200' elevation.
- AI removed
- Chevy605 Pipes.