What gas mileage do you get?

You are correct, aju, because if you are producing more horsepower you are using more fuel in the absolute sense...but, keep in mind, at the torque peak, you are using fuel more efficiently.

Examples from the chart for the D1A:

4000 RPM = 26BHP = 255g/HP-Hr = 6630g/Hr

7000 RPM = 55BHP = 210g/HP-Hr = 11,550g/Hr

In the above example at 7000RPM you are generating 2.12 times more power than you are at 4000RPM......BUT you are only using 1.74 times more fuel because of the greater efficiency of the engine at 7000RPM.

Unfortunately on most modern roads it is very difficult to ride at 4000 RPM at highway speeds without rowing on the gearbox lever continuously because you are 'wayyyy back down the torque curve. You are just not producing enough torque to move the bike and rider mass/frontal area against the rolling and wind resistance.

Around town, or on surface streets it is eminently feasible to ride at 4000 RPM in, say, third gear and you'll get excellent mileage....but this is also impractical because around town/on surface streets you are usually stopping and starting and that defeats the whole purpose of steady state 4000 RPM riding.

Sooooo....the ideal solution is to ride on secondary roads with no stop and start traffic and at modest speeds in 3rd or 4th gear at 4000 RPM. Your road speed will be slower than you may normally be used to but you WILL be using less fuel in absolute terms because you're using less power.
Like life, riding is full of compromises.

N0NB wrote:

My SR is consistently 39-40 MPG. The 650 hit 42. I haven't seen any better than that from either.

Ditto on that here too. I can get about 40MPG riding alone but only about 38MPG with my wife aboard. This is with a sprocket ratio of 16/40.

Pisses me off that my friends who ride Harley's consistantly get 44-45MPG! AND they have more than twice the displacement!

Oh well...my bike is paid for. I guess that counts for sumthin'

I am getting a honest 50 mpg from my KZ1000P below 65MPH anything over that speed the mpg drops to mid 40s ,, I still have the 630 chain but with 15 - 33 gears or 2.20 ratio ..or 3200 rpm at 65 mph , 3800 rpm at 70 , 4400 rpm at 75 works for me

I just returned from a 2,500 mile road trip on my '82 KZ650 CSR, and want to pass along a few comments. The bike is geared very high: 13 front and 26 rear. It has Mikuni BS32 carbs. I was riding with a group, so we could compare mileage, etc.

1. IMHO, a carburetor does not get the best MPG at wide open throttle, since it richens the mixture as the throttle opens beyond a certain point.

2. The faster you go, the greater amount of air has to be pushed aside, which consumes power and fuel in the process. With all other things being equal, you will get better mileage at slower speeds.

3. High RPMs generally do not get as good of mileage as lower RPMs, unless the power is so insufficient that the throttle must be opened rather wide.

4. At the RPM where maximum torque is generated, an engine probably does put out the most horsepower per unit of fuel consumption. On a dyno, with no wind to push, and lots of power being generated, you might start to see some favorable figures. But we are not riding under this condition.

5. At slow speeds, a bike with smaller displacement will generally get better mileage than a large displacement. But as speed increases, the gas mileage decreases for the smaller bike, to a point where the larger displacement bike will actually get the same or even better mileage. The larger displacement can run fast with less penalty than the smaller engine.

5. I have found the best mileage is obtained by using high gear and running about 40 MPH. Of course, you can't get anywhere. I have done numerous studies on mileage, and found my actual mileage has averaged as follows:

40 MPH --- 62 MPG
50 MPH --- 59 MPG
60 MPH --- 57 MPG
70 MPH --- 54 MPG
80 MPH --- 49 MPG
85 MPH --- 43 MPG

Hope every body is not bored to sleep by this.

My 1988 Voyager XII with a 1200cc engine and four Keihin CV32 carbs gets 42 mpg at 75-85 mph and lots of throttle action and 45 mph at 55-65 riding easily. Both these figures are two-up riding (in comfort with the stereo blasting).

What RPM is your Voyager turning at 65 MPH, George? My 650 SR is turning at 5400 RPM for 65 MPH with everything stock but the rear sprocket is down three teeth to 38.

My 1980 KZ70 LTD with wiredgeorge carbs, stock air box with K&N filter and stock exhaust is getting 48-50 mpg with my riding style, mostly local runs, some evening trips of about 20-30 miles. I am very pleased with the mileage so far, but I may gear it up when I replace the chain later this year.


Mark

This Just In !!!!
My second tank this season turned up 49+ MPIG (~39.3 MPUSG)
with half and half city/country riding. As well, none of the riding was done in temps over 17 deg C (64 deg F) and a lot of the city riding was done in temps of less than 13 deg C
(55 deg F) so everything was kind of stiffer than it would have been at 25 deg C (~78 deg F) and above. The cooler temps contribute to rolling resistance as well as internal engine resistance.
Yes, this is splitting hairs but it's amazing how big a difference many little things add up to in the end.
When the temps in Cowtown consistently exceed 25 deg C, I expect to see a nice improvement, even with the stock (fairly deep) gearing.
My .02.....

1977 KZ1000 with straight pipes and smoothbores. K&N Air filters. I get between 38 to 41MPG.

Depending on depending.

Speed limit?

Is there a speed limit?

I got 34 mpg on a 73 z1 with pods 28mm mikuni's vance n hines 4into 1 with no baffle. I checked the milage on a road trip doing 90 mph for roughly 100 miles with a passenger. I believe riding solo at 70 mph I could get 45 to 50 mpg but havent tried that out yet. My tach cable broke on the trip so i don't know the revs, but I think at 90 with my gear it is about 5800 rpm

Just filled the tank on the 750 twin again the other day. 156 miles since the last fill up, and it took 1.86 gallons. That's 83.87 mpg.

That's riding in fuel economy mode though, slow accel and steady 60 mph cruise, but at $4.00 per gallon for regular unleaded I'll probably continue riding the same way (most of the time anyway).

GPzInfested got 50 mpg on his 750 Turbo while riding with me, by himself he gets 35-40 mpg, I know what he's doing when I'm not around

MILES per gallon?:huh:...No idea.
SMILES per gallon?...about 400! :woohoo: :laugh: