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Old 04-10-2007, 11:35 AM   #1
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Question about motorcycle mpg

I was looking at motorcycle mpg on this site http://www.totalmotorcycle.com/Motor...uide/index.htm and I'm curious why fuel economy is relatively poor compared to that of a car. For instance, several of the honda 750cc models get approx 45 mpg. Now a car that's several times heavier with twice as many wheels (greater rolling resistance), a much larger frontal area, and an engine twice as big can get the same mileage.

Based on the car's fuel economy, you'd expect a motorcycle with an engine half the size and much less rolling resistance and smaller frontal area could do much better.

Are motorcycles tuned drastically differently -- like for high revs and hp? Can they be re-tuned for improved fuel economy?
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Old 04-10-2007, 11:42 AM   #2
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it's actually a lot of little things acting together.

They're definetly geared different, and more towards acceleartion than cruising (exeptions like Harleys of course) For example, my bike runs a good 5500 rpm's at 60 in teh highest gear.

Aerodynamics aren't very great on a motorcycle either. The air gets VERY dirupted by the rider, as the only place it is ever attached is the very front of the bike. The very small frontal area helps this a lot though.

The tires are much smaller, with less contact area. But they're also MUCH softer. The average motorcycle tire only lasts thousands of miles, not tens of thousands.

There is DEFINETLY room for improvement, as Craig Vetter has done a GREAT job of proving.
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Old 04-10-2007, 11:51 AM   #3
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You are correct about most motorcycles being tuned differently and running higher RPM. My old Honda CX500 puts out 50 hp, redlines at 10,000 RPM and gets about 45 mpg. On the freeway it's turning about 6000 RPM. My Suzuki Swift car turns about 2500 RPM on the freeway and gets better mileage than the bike.

Some small and slow motorcycles get very good mileage, like the 50cc or 70cc Hondas used in most third world countries. They'll do over 150 mpg.

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Old 04-10-2007, 11:59 AM   #4
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The aerodynamics are really bad. A Metro probably has less aero drag than a person on a motorcycle.

Plus they are tuned for performance instead of economy.
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Old 04-10-2007, 01:35 PM   #5
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[QUOTE=northboundt

Are motorcycles tuned drastically differently -- like for high revs and hp? Can they be re-tuned for improved fuel economy?[/QUOTE]


They can be tuned for economy, much easier than most cars. Almost all bikes have carbs with changeable jetting, also very easy to change the ignition timing.
If you had some mechanical skills you coud also play around with cam timing or with different cams to change the power and torque to lower rpm range.
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Old 04-10-2007, 01:37 PM   #6
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Not to mention a larger rear sprocket. This was an aftermarket option for my Ninja 250 (14k redline!).
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Old 04-10-2007, 01:39 PM   #7
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BTW - this same question came up in a previous thread...

Motorcycle mileage
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Old 04-10-2007, 01:44 PM   #8
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Quote:
Originally Posted by MetroMPG View Post
Not to mention a larger rear sprocket. This was an aftermarket option for my Ninja 250 (14k redline!).
Ah yes, I forgot about that. Also very easy to change gearing on bikes compared to cars.
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Old 04-10-2007, 02:31 PM   #9
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I think you would want a smaller rear sprocket to reduce cruising revs.

I always wanted to hear one of those Ninja 250s hit the redline. Had to sound like an F1 car...
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Old 04-11-2007, 07:25 AM   #10
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Thanks for the replies. Sorry for posting in the wrong section. Wondering if there is a good bike anyone can recommend that has high FE potential and still enough power to get out of a jam if necessary. Also, parts should be available and plentiful. I did buy an old Suzuki GS400 a little while back, planning to fix it up, only to find later that engine parts were not available for a rebuild. So I sold that one and I'm toying with the idea of getting another. Thanks
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