Causes for poor fuel economy? (Looking for suggestions)

[JJ_08 11]

I'm getting very poor fuel economy , and was hoping to get ideas from the brain trust here on things I can check.  I was getting about 35mpg when I first got my FZ. 

Things I have tried so far:  valve adjustment, changed plugs, cleaned injectors, cleaned and sync'd throttle bodies, changed oil, replaced my chain (x-ring), replaced air filter (OEM), and checked that both front and rear wheels spin freely.  Appears to be a stock ECU (maybe it's flashed? but I can't imagine why...), stock exhaust, and stock airbox with snorkel.  Gearing is also stock (16/43).

I also realized after I bought the bike that it had been crashed at some point, and discovered that the gas tank had been damaged, resulting in a leak at the front hinge weld.  I could constantly smell gas and noticed a visible leak from the tank.  I brazed the crack, pressure tested the tank, and believe it it no longer leaking (no signs of any gas leaking, no smell).

After doing all of that, my gas mileage averages around 38-40mpg.  (Both according to my dash, and checked by dividing the mileage on my odo by the number of gallons I fill up at the station - but not checked against GPS.)

90% of my riding is "spirited" riding on my favorite backroads.  I've noticed that when I'm on the highway or riding around town, my instantaneous mileage goes up to the high 40s-5os+.  Unfortunately (fortunately?) I use my bike primarily for recreation and almost all of my riding is in the twisties.  That being said, I'm hearing from other folks that even spirited riding should yield better fuel economy than what I'm getting.

I'd love to get some ideas from y'all on other things I can check.  What am I missing here?  What else could be causing this abysmal gas mileage? 

Thanks in advance!

Edited December 31, 2022 by JJ_08

[mjh937 1,904]

Just for reference I am getting in the high 40’s mpg with spirited, fun riding.  I have a 2WDW tune and O2 sensor removed, otherwise my bike is mostly stock (MRW air filter and lid but stock exhaust) and I bought it new in 2014.  It seems you should be getting in the 40’s easily. 

[M. Hausknecht 361]

Dunno that I have much to offer here but it occurs to me that, conceptually, there are three possibilities: (1) fuel is leaking; (2) motor is running rich: and (3) you're using more throttle than other folks under reasonably similar circumstances.

As you're no longer smelling raw gas, it seems  you've eliminated leaking fuel as a possibility.

The motor could be running excessively rich for many potential reasons (a flash to the ecu, bad sensor(s), clogged air filter) but, if so, the spark plugs' appearances should reveal it. So, what did the plugs look like when you replaced them? The stock plugs are pretty "hot" so the insulator around the center electrode should have virtually no color to it when the mixture is more or less correct with pump gas. Have you checked the plugs again since replacing them? Bad sensors should throw a code and activate the malfunction light.

We all ride a little differently, so I suppose your spirited riding could use more fuel than other folks' spirited riding. Are you a bigger guy? While riding, do you tend to ride between 4-6000 rpm or more likely between 7000-9500 rpm? You're not far off from what others report so a difference in revs/throttle could be why.

One other thing that just occurred to me. Do you tend to buy your gas from the same place each time you fill up? We tend to think that all pump gas is the same but I've periodically noticed a few mpg differences in 4 wheel vehicles between gas stations. 

 

[JJ_08 11]

@M. Hausknecht Thanks for your analytical approach to my question!  Based on your and others' responses, it seems like something is amiss...

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what did the plugs look like when you replaced them?

Here's a pic of one of the old plugs I pulled - I thought it looked more or less in the range of normal?:

I haven't checked the plugs since I replaced them, but that's a good idea.

 

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While riding, do you tend to ride between 4-6000 rpm or more likely between 7000-9500 rpm?

I don't think I ride particularly hard (I'm definitely the slowest guy among my friends!).  I went back and looked at some GoPro footage and see that my tach is typically in the 6000-8000 RPM range for most of the time I'm in the twisties, and my instantaneous MPG reading floats between low 20's - mid 30's.  In the city/highways, my RPMs are more like 4-6k and MPGs are in the high 30's-40's.

 

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Do you tend to buy your gas from the same place each time you fill up? We tend to think that all pump gas is the same

This is interesting - I often get my gas at the same Chevron station (simply because it's on the way home), but I've also gotten gas plenty of times at random other stations (both "name brand" and "off brand" stations).  I haven't noticed a marked difference, but will pay attention to that...

 

16 hours ago, M. Hausknecht said:

The motor could be running excessively rich for many potential reasons (a flash to the ecu, bad sensor(s), clogged air filter)

I'm not getting any codes, but now you've got me wondering about sensors.  Any you would suggest checking in particular?

I'm also starting to wonder if my ECU might be flashed.  I don't see any markings on it, and it would be odd since my bike has a stock airbox and exhaust, but I suppose it's possible the previous owner reinstalled the stock exhaust/airbox before selling it.

Some other potential clues:

I've noticed that the bike hesitates with hot starting.  For example, if I've been riding, and the coolant temp is reading >190 deg F, if I try to re-start the bike, I sometimes have to try 2-3 times before it'll start, and I often have to hold the starter down +/-5 seconds before it catches.  If I crack the throttle open while thumbing the starter, it seems to help with hot starts.  This problem seems to have gotten better after I adjusted the valves, but it still happens occasionally.  Cold starts are not an issue.

I've also noticed my bike gets up to temp more quickly and gets hotter than other bikes I've owned.  I see my coolant temp routinely going above 200 deg F, and the fan kicks on pretty often if I'm in stop-and-go traffic or if I don't keep moving.  I'd convinced myself that this was normal to the CP2 motor, and wasn't a problem... but am I wrong? 

 

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Are you a bigger guy?

Neglected to mention earlier that I'm around 145 lbs, fully geared, soaking wet. 

[Triple Jim 490]

Just for one more piece of information, next time you have your camera out, post a photo of what your head pipes look like.

[cornerslider 794]

It sounds like you have checked everything that could contribute to less than expected MPG...My guess the issue is in your right wrist . The term "spirited-ride" doesn't mean the same thing to everyone. When I rode my modified 07 on the street (un-spirited), I usually got 50-55 MPG. I have since turned it into  dedicated race-only bike, and get 20-25 MPG when racing (on the same pump gas). Have you gone on a ride and "tried" to get the best MPG possible? Maybe take it out on a road that doesn't have a lot of stoplights, and just cruise at around 55-60 mph. I know it sounds pretty boring, but might give you the answer of "is it the bike- or the right wrist"- 

[shinyribs 1,669]

Low 40's mpg is what my bike did off the showroom floor. New toy, so I was constantly hammering it. As years went by my average mpg stayed around 50-52 as I'd gotten used to the bike and was able to carry more speed through the corners which results in not having to accelerate as hard since you're not losing speed in the corners. I was actually riding faster, but using less "power" to do it.  There's a lot of factors at play. 

 

These bikes are geared short ( and I love it) so they're not really easy on fuel on the open road. I could get low -mid 60's cruising around 45-50mph, but running on a 75-80mph interstate would have the fuel mileage plummetting below 40 pretty easy. 

 

I've never owned a bike who's mpg was so sensitive to rpm.  Hard hooning/high speed interstate riding on my FZ 09 will give me about 38mpg while easy cruising can get up to about 42mpg. Nowhere near the nearly 20mpg variance the 07 gives me. 

[JJ_08 11]

On 12/31/2022 at 6:42 AM, cornerslider said:

Have you gone on a ride and "tried" to get the best MPG possible? Maybe take it out on a road that doesn't have a lot of stoplights, and just cruise at around 55-60 mph. I know it sounds pretty boring, but might give you the answer of "is it the bike- or the right wrist"- 

@Triple Jim suggested this in another thread as well!  Makes a lot of sense, and it's likely the easiest and most reliable diagnostic I could do.  Now I just need to convince myself to ride sensibly through an entire tank of gas!

In my helmet, I'll be repeating: "Ride like a good boy. Eco light is your friend. Ride like a good boy. Eco light is your friend."

I find the FZ07 remarkable in how friendly and approachable it is, while having the ability to bring out the inner hoon in me. 

[Triple Jim 490]

2 minutes ago, JJ_08 said:

In my helmet, I'll be repeating: "Ride like a good boy. Eco light is your friend. Ride like a good boy. Eco light is your friend."

If you find a twisty enough road, you don't need to open the throttle to get your adrenaline rush.

[JJ_08 11]

Between a hectic few weeks of work and the storms here in Northern California, I haven't been riding much lately, but during the few miles I've put down, I cannot seem to average better than 40mpg no matter how hard I try. 

The only way I seem to get the instantaneous MPG reading up is if I cruise around with a steady throttle at 30mph in 5th or 6th gear.  But as soon as I open the throttle, it drops down to the 20's.

I'm starting to think that my ECU might be flashed (or there's something else wrong with my motor?).  Not sure there's any way to tell, short of sending my ECU in, or swapping it with a known stock ECU.  I'd be curious to try riding a FZ with a stock ECU to see if I can tell a difference.

The bike seems to run well other than the poor fuel economy, and fortunately, I use it mostly for recreation, so gas mileage is not as big a concern to me as it would be were commuting on it.  Part of me thinks I should take an attitude of "if it ain't broke, don't fix it" - but it just bugs me that something doesn't seem quite right!