When I bought this bike I got about 45 MPG.  Now I get a little over 30 MPG and bike has now over 100K miles.  I know the fuel power density has decreased in the gas here in California, since I noticed similar but not as great drop in fuel mileage.  What would you think would be an expected fuel mileage for this age bike and if you have one, what do you get?

I have a few Ks, from 83 to 96, they don't like ethanol fuel and since we got E10 [10% ethanol] here it has really increased the fuel consumption, sometimes similar to yours. Depending on which one I took, I would get 10-12 miles per litre, now same bikes give me maybe 8-9 miles per litre and that's all with good systems, clean injectors etc.

I've seen 51mpg many times at 70mph out on the Canadian prairies. It drops to about 45mpg under more spirited riding. I've never serviced my injectors, but put in a full container of Sea Foam injector cleaner at the beginning of each riding season.

RS Rider wrote:I've seen 51mpg many times at 70mph out on the Canadian prairies. It drops to about 45mpg under more spirited riding. I've never serviced my injectors, but put in a full container of Sea Foam injector cleaner at the beginning of each riding season.

How many miles you have on that bike?

letsgetpractical wrote:

RS Rider wrote:I've seen 51mpg many times at 70mph out on the Canadian prairies. It drops to about 45mpg under more spirited riding. I've never serviced my injectors, but put in a full container of Sea Foam injector cleaner at the beginning of each riding season.

How many miles you have on that bike?

 
49120 miles.

RS Rider wrote:

letsgetpractical wrote:

RS Rider wrote:I've seen 51mpg many times at 70mph out on the Canadian prairies. It drops to about 45mpg under more spirited riding. I've never serviced my injectors, but put in a full container of Sea Foam injector cleaner at the beginning of each riding season.

How many miles you have on that bike?

 
49120 miles.

thats about what I used to get when I bought this bike years ago with 30K on it.  Now it has over 100K on it.  Has a problem with warm up and idle but on the road does fine but bad mileage.  I am going to change and inspect plugs and check wires.

RS Rider wrote:I've seen 51mpg many times at 70mph out on the Canadian prairies. It drops to about 45mpg under more spirited riding.

letsgetpractical wrote:thats about what I used to get when I bought this bike years ago with 30K on it.  Now it has over 100K on it.  Has a problem with warm up and idle but on the road does fine but bad mileage.  I am going to change and inspect plugs and check wires.

Practically speaking, if the last time the valve clearances were adjusted, the throttle bodies were balanced, and the fuel and air filters were replaced is unknown or not recalled, there isn't much of a baseline for an accurate diagnosis.

I have always calculated fuel efficiency with my vehicles and with my Bricks I see a pretty consistent 45-48 miles per U.S.gallon in most of the riding I've done on the 5 bricks I've owned.  One difference is when running fully loaded at 85+mph into the wind on the Interstate I will see the mileage drop to as low as 38-40mpg. 

I have owned bikes with anywhere from 28K miles to 130K miles and they all get in the same range with the 16valve K100's getting 1 or 2 mpg better than the 2 valve models(up  to 49-50mpg). 

I mostly run E10 87octane but have not noticed a significant change in efficiency with 91octane ethanol free.  My bikes are carefully maintained with all maintenance done at the recommended intervals(or annually) and I tend to ride like the old man that I am.  I would guess that running a little more aggressively at higher rpm might reduce efficiency a bit.

I have a low milage K100 rs ( 91K kms), I know just run in.
I get between 45 to 47 MPG/US depending on the wrist!
That's using 95 octane usually from BP.

letsgetpractical wrote:When I bought this bike I got about 45 MPG.  Now I get a little over 30 MPG and bike has now over 100K miles.  I know the fuel power density has decreased in the gas here in California, since I noticed similar but not as great drop in fuel mileage.  What would you think would be an expected fuel mileage for this age bike and if you have one, what do you get?

First thing I would do is check the temp sensor resistance.

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/tempsensor/tempsensor.htm

I'm with Laitch. At that mileage throttlebodies, valve clearances, filters and crankcase breather hose all need looking at to get a good baseline.

I have changed the temp sensor with an OEM type not a cheap one.  I am interested if anyone using California fuels has had a similar experience.  I have new plugs ordered and throttle body balancing tool ordered.  I dont have any black smoke indicative of excess fuel and the bike runs good on highway.

I've ridden a lot in CA and fuel was never a problem.

duck wrote:I've ridden a lot in CA and fuel was never a problem.

The question is did you fuel up in California?  I run 2 Nissan trucks here and have noticed significant fuel mileage drop over the years.  And they have smog checks every 2 years and are tested for emissions with no problems so there is no issue in engine maintenance/performance.  California just passed another "carbon reduction" action that will raise the price again per gallon at estimated $.65/gallon.  I am sure that is going to be another power density drop in the fuel.  And the fuels I believe vary according to where they are sold in California.  Rural areas have different blends and are exempt from smog check requirements.  So you could fuel up in outlying areas and get different fuel mileage results.  At least that is what I think.  I would like to hear from somebody in the LA or Bay area or Sacramento/Stockton area and see what kind of mileage they get on their K100

letsgetpractical wrote:

duck wrote:I've ridden a lot in CA and fuel was never a problem.

The question is did you fuel up in California?  

Yes. All over SoCal and the coast.