poor gas mileage

Message

pigsbladder · Thu Jul 26, 2007 4:16 am

Alright, so I've had my spirit 750 for about a month now and after quite a few fill ups I'm kinda concerned about gas mileage.

I'm only getting around 42 mpg instead of the 50-55mpg it claims. Do you think there is something wrong?

Bike has 11k miles, pipes and I have saddlebags on it. (which I thought where lame at first, but have come in super useful, not that I carry a lot in them)

Is there a few things I can check? Is the mpg affected more by biker weight (read fat boy), windy conditions etc over cars?

Thanks

jonnythan · #2 Unread post by **jonnythan** » Thu Jul 26, 2007 4:52 am

Rider weight and size, driving conditions, etc all contribute. Short trips give less gas mileage than longer trips because cold engines use more gas.

42 does sound low considering what I just found people reporting on a Google search... so I'd do a tuneup. Replace the spark plugs and the air filter, run a can of Seafoam through it. Check your tire pressure.

Ian522 · #3 Unread post by **Ian522** » Thu Jul 26, 2007 5:05 am

Ive found that the "claimed" mpg is usually a bit optimistic for real world conditions.

Your riding habits have alot to do with it as well. On my 450 ive gotten as high as 60mpg when riding a steady 65 on flat highway trips, but as low as 40mpg when flogging the bike around town.

Flesher · #4 Unread post by **Flesher** » Fri Jul 27, 2007 2:56 pm

Just to cover all bases ... check your choke and make sure that it is not binding, you may want to lubricate the choke cable, it may be binding and holding the choke partially open even though the knob is at the closed position. Riding around with your choke open will surely affect gas mileage.

JC Viper · #5 Unread post by **JC Viper** » Fri Jul 27, 2007 5:54 pm

Proper tire pressure means less drag which can improve mileage. Always check your tires weekly.

Another thing to check is the air filter, a dirty one will net you less gas mileage.

Something else to keep in mind is the RPM you keep your bike in while riding. The harder you work the engine the more gas will be used. And of course in town driving will yield less gas mileage than on a highway.

I've managed to get 56 MPG from my Vulcan 500 by getting a better air filter, a windscreen to reduce buffeting, and changed the sprockets to drop the RPM at speed.

#6 Unread post by **Sev** » Fri Jul 27, 2007 6:33 pm

Most new owners tend to watch their fuel mileage drop off as they own the bike for longer and longer. Reason being - they accelerate harder, ride faster, run harder. And this uses more fuel.

Such is life.

blair · #7 Unread post by **blair** » Sat Jul 28, 2007 7:11 am

Freeway mileage is a lot less than street mileage, so maybe you're riding more freeway than street.

Yes, this is the reverse of cars.

Bikes are light, so they get an advantage in stop-and-go driving. Cars are more aerodynamic, and because of this can use a much bigger gear on the freeway than the street, so they get an advantage in freeway driving.

#8 Unread post by **dr_bar** » Sat Jul 28, 2007 7:19 am

Sev wrote:Most new owners tend to watch their fuel mileage drop off as they own the bike for longer and longer. Reason being - they accelerate harder, ride faster, run harder. And this uses more fuel.

Such is life.

+1

I found that anything over 3000 RPM, is a killer on mileage. The higher the RPM gets, the mileage drops exponentially.

blair · #9 Unread post by **blair** » Sun Jul 29, 2007 5:21 am

dr_bar wrote:
Sev wrote:I found that anything over 3000 RPM, is a killer on mileage. The higher the RPM gets, the mileage drops exponentially.

It's a matter of power curve. The ones you normally see, hp vs. rpm, are kind of parabolic, but there's another set based on throttle-plate angle that are bathtub shaped. Meaning that it's pretty flat over a middle throttle setting, but very steep at low and high settings. That's where your fuel efficiency would be worst.

It's pretty easy to tell at the low end because the engine lugs. I think at the high end you just notice you're opening up and not getting much more speed out of it.

I haven't seen such curves for injected engines, but I expect they're different.

Nalian · #10 Unread post by **Nalian** » Sun Jul 29, 2007 7:07 am

blair wrote:Freeway mileage is a lot less than street mileage, so maybe you're riding more freeway than street.

Yes, this is the reverse of cars.

Bikes are light, so they get an advantage in stop-and-go driving. Cars are more aerodynamic, and because of this can use a much bigger gear on the freeway than the street, so they get an advantage in freeway driving.

That is the complete opposite of both bikes I have owned. I get between 52-55 street, and on my road trip doing between 50-80mph I got as high as 63 on the highway with my 650r. Normally it is around 57-60.