Fuel economy heading south - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 11 (permalink) Old 06-09-2006, 12:11 AM Thread Starter
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Fuel economy heading south

I have a 2002 vulcan thats fuel mileage is dropping on.A month ago I hade to make a 70 mile trip to get some new tires put on,45 miles of the trip was on the interstate running about 80 miles an hour.Every since that trip my mileage per gallon has been around 46,before the trip it was around 50.I cleaned and regaped the plugs and cleaned the air filters,it seems to run fine.It was a Kawasaki dealership that did the tires is there anything they may have done to cause this.
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post #2 of 11 (permalink) Old 06-09-2006, 04:52 AM
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Air pressure in the front tire can play a big role in your mileage readings.

Maybe double check what the shop put in there.

On my truck, 2 sets of the exact same size tires, one with normal tread and one with more aggresive, offroad type tread, can give me about 3.5 - 4.5 MPG difference.

It's hard to get a good estimate of MPG without knowing that all the variables are accurate.


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post #3 of 11 (permalink) Old 06-09-2006, 07:55 AM
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What tires did you put on? Did you go with the 110 in the front? A newer/bigger/overinflated front tire would appear to drop the milage because it doesn't go around as many times for the same distance.

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1995 VN750 (Black w/ 2004 tins - no teal)
2003 VN750
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post #4 of 11 (permalink) Old 06-09-2006, 08:25 AM Thread Starter
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I replaced the the stock tires with Bridgestone spitfires s11's.The dealership put 35 pounds in each.I adjusted the pressure to 31 front and 33 back.the front tire is .1 of an inch larger in diameter.
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post #5 of 11 (permalink) Old 06-10-2006, 02:30 PM Thread Starter
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post #6 of 11 (permalink) Old 06-12-2006, 06:13 PM
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Moontroll, like someone mentioned above, there are too many variables to guess why your gas mileage has gone down some. It is entirely possible that the new tires are it alone. If the new tires aren't identical to the old tires that were replaced, identical in circumference and weight, as well as tread design, they will have some effect on performance of your bike. If the front tire is slightly larger, it will make less revolutions at the same speed and distance, showing slightly slower on the speedometer, and less miles on the odometer. If it shows less on the odometer and you are used to going 120 miles on your trip meter before filling up, and it usually took 2.4 gallons, (roughly 50 mpg) and now after the new slightly larger front tire, when you fill up at 120 miles on the trip meter, (you've actually gone 130 miles) it takes 2.6 gallons (roughly 46 mpg when figured on 120 miles traveled) but you actually traveled farther than your trip meter says. It might not make that big a difference, just having a tiny bit larger tire, but the tire probably weighs a tiny bit more as well, and may have a different tread design and the rolling resistance may be greater. You get the point, I'm sure.

My 99 jeep wrangler had 31" tires on it since I bought it and put them on. It got right at 20 mpg in combined driving. 3 years later I put on a lift of 2.5" and put on new, very aggressive treaded mud grips, still in 31" tires. These new tires combined, I'm sure, with the 2.5" lift, dropped my gas mileage to 15-16.

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post #7 of 11 (permalink) Old 06-21-2006, 11:39 PM
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Has anyone brought up ethanol in the fuel? My milage has been been dropping over the last couple of weeks and the engine is not running quiet as smooth as it did a few weeks ago the only thing that I can think of that is different is the new 10% ehtanol in the fuel. Has anyone else seen anything similar?
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post #8 of 11 (permalink) Old 06-22-2006, 02:51 PM
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Moontroll - Good to see another Arkansan. Tire pressure is a big thing. I had been getting 46 until I bumped mine up to 35-ish front and back. Now I get 50. Also, with the heat we have, very little choke is necessary to start. That's another big gas hog.

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post #9 of 11 (permalink) Old 06-23-2006, 01:35 PM
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Question New vn750 mileage

During breakin my mileage has only been around 24 mpg, is that
normal for breakin under 100 miles on the machine?

Didn't receive an owner's manual yet, can anyone tell me how
to determine how much oil is in the engine?
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post #10 of 11 (permalink) Old 06-23-2006, 01:48 PM
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Quote:
Originally Posted by norsseman
During breakin my mileage has only been around 24 mpg, is that
normal for breakin under 100 miles on the machine?

Didn't receive an owner's manual yet, can anyone tell me how
to determine how much oil is in the engine?
See:
https://www.vn750.com/forum/showpost....49&postcount=9

Deuce (Loran Naperville IL)
1995 VN750 (Black w/ 2004 tins - no teal)
2003 VN750
Both have: - F&S Bags & brackets
- Corbin seat w backrest
- Progressive suspension.
- Kury iso goldwing grips
2 1983 V65 Magnas
2 1985 V65 Mangas (1 which is in many parts)
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