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Old 11-09-2011, 05:04 AM   #1 (permalink)
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Restrictions and fuel consumption

Will restricting a larger, let's say, 500cmc bike, like the gs500 for example, reduce it's fuel consumption?

I understood that the gs500 gets about 5l/100 km in town ( or 50 mpg or so ), under normal conditions ( not trying to drive economically ) and I was wondering if restricting it, and also if using various techniques to reduce fuel would make it reach let's say, 4l/100 km or less. ( around 60 mpg, but it would be nice if I could reach 70 mpg on it )

Just got my motorcycle riding license a few months ago and I was wondering what to buy; I commute everyday to work around town, and a very crowded one, average speed is very low for cars, about 20 km/h for the whole trip; fuel consumption is important for me, also size and weight. I will be driving only in the city with the motorcycle that I will get.

I am undecided between a few models:
- a small underbone like the honda innova 125
- honda cbr125
- yamaha virago 250, suzuki tu250 in the 250 cmc class
- suzuki gs500, honda cb500, kawasaki er-5, in the 500 cmc class

What I care about is:
- being thin enough to fit between cars when the traffic is blocked and get
for example the cbr125 is just 67 centimeters wide, that's great for going past cars in trafic
- great fuel consumption
- a reliable engine with low maintenance

I like the 500cmc ones because they are more reliable engines, and also have more than enough power, but I don't appreciate their fuel consumption ( even though they are considered very economical for their size ).
And if I get one, I think it's a good idea to restrict it since I am a beginner ( I have been riding a 49cmc moped for the past 4 months, that is all the experience I have on two wheels ).


Last edited by adrian_mirea; 11-09-2011 at 05:13 AM..
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Old 11-09-2011, 05:12 AM   #2 (permalink)
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hey bud, welcome to ecomodder, you'l find everything you need here, technical and straight forward,

can you please be a little more exact and what you mean by restricting your back,

eg: restricting exhaust, air flow??

the more technical you can get the better we can heklp you calculate and decide what is good for ya, although testing does help
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Old 11-09-2011, 05:17 AM   #3 (permalink)
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Well, I don't know exactly... I guess that I was thinking about restricting the carburetor to reduce the fuel intake; maybe even the exhaust would help, I don't know.
50hp is a bit too much for what I need and I am more than willing to trade hp for mpg.
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Old 11-09-2011, 09:01 AM   #4 (permalink)
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You could put a restrictor plate in the air box, more or less blocking it off with a plate that has a hole in it that only lets a given amount of air pass, but that will only limit performance and not improve mileage other then preventing you from going as fast, however you could instead redesign the air box and air intake to be all around smaller and you should see an improvement if it was the right length as well, to get the math right you are going to need to read up on air intake design or find a calculator that helps you design air intakes but just randomly reducing the size will not help unless you are really lucky, same goes for exhaust size.
Personally I would go for something like the Honda CBR125, I've read a bit about them because I have one of the old CB125 motorcycles that is really impressive and with the CBR125 they improved the gas mileage and top speed and for someone who is used to mopeds it's going to be easy to handle.
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Old 11-09-2011, 09:16 AM   #5 (permalink)
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If you are concerned mainly about mileage, I'd skip the 500cc bikes.

Look into the 250s. Enough power and more capable of serious MPG numbers.

125cc would be even better if you don't need the acceleration and top speed of a 250 and you aren't a large person.

It's up to you if you want a true motorcycle or a step-through like the Innova.

A 500 is pretty large and heavy compared to the 250s and 125s, which makes it not as good for a first bike anyway IMO.


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Old 11-09-2011, 01:05 PM   #6 (permalink)
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I think for slow speeds the smaller engine will almost inevitably win, so I'd go for the little CBR or, even a bit smaller (also somewhat weaker), the CBF125. If you'd like to go 2-up much, or mostly out of town, you may better off with at least a 250.

I, personally, chose an even larger because I commuted over a freeway that time, and I fell in love with the F650CS. After I found it a rational choice, of course. The fuel injected models have an appetite very much like a 250. At least they drink less than the GS500. The mentioned 125s are, of course, better in this respect.

Note that this is my first bike, there's nothing wrong with choosing a larger one to begin, it took some time to get used to the weight, but these singles are well-mannered and predictable so their behaviour is not a problem
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Old 11-09-2011, 01:13 PM   #7 (permalink)
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Restricting the intake or exhaust will add work for the engine to overcome to produce power. Not likely to reduce fuel consumption. For your stated purpose go with a 125 or 250 depending on how fast people accelerate from a stop. See what is popular in your city and ask the riders what they think about thier choice.
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Old 11-09-2011, 01:30 PM   #8 (permalink)
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Honda claims 77 mpg US for the CBR250R.
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Old 11-09-2011, 07:55 PM   #9 (permalink)
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Welcome to ecomodder.

Quote:
Originally Posted by adrian_mirea View Post
Will restricting a larger, let's say, 500cmc bike, like the gs500 for example, reduce it's fuel consumption?
The carburetor versions are often restricted by reducing the intake diameter (plate with a small hole between carb and engine).
It's limiting the air flow, thus also limiting the fuel flow, but I wouldn't expect wonders in the overall fuel efficiency.

Quote:
and I was wondering if restricting it, and also if using various techniques to reduce fuel would make it reach let's say, 4l/100 km or less.
If I can get 4L/100km out of a Volvo S40, you should do better on a bike

You'll have to change the way you ride, it'll be far more efficient than restricting a bike.

Quote:
I commute everyday to work around town, and a very crowded one, average speed is very low for cars, about 20 km/h for the whole trip; fuel consumption is important for me, also size and weight. I will be driving only in the city with the motorcycle that I will get.
In that case, I'd opt for a 250 or even 125cc, with fuel injection.


Quote:
- a small underbone like the honda innova 125
- honda cbr125
These are very efficient little engines.
The Innova averages less than 2L/100km for 98 users !
Overview: Honda - Innova - Spritmonitor.de

Top of the list, Evomoto with 1.1L/100 km is a member here, but he uses a highly modified Innova.


The CBR 125 does almost as good.
Overview: Honda - CBR 125 - Spritmonitor.de
On the CBR, the gearing can be changed so it makes less rpm at the same speed - but don't push it too far on a small 125cc.

Do you get the CBF125 in Romania ?
A bit wider, but the seating position will be more comfortable in town than on a CBR.


Quote:
What I care about is:
- great fuel consumption
- a reliable engine with low maintenance
That just screams Honda 125cc with fuel injection

The 500cc are oversized for what you say you need.


An MP3 125cc hybrid may look attractive to the fuel-conscious, but it's horribly expensive (almost 3 times the price of the CBR) , and the fuel economy seems to disappoint a bit.
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Old 12-10-2011, 05:04 AM   #10 (permalink)
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I want my convert my gasoline car to diesel.Can any one give me any suggestions what things i should consider before doing that?

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