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Discussion Starter #1
Hello,
I have been averaging about 40 mpg on my 2011 vstrom 650. About 6 months ago i was getting 48-52 mpg. I changed my chain and sprockets, air filter and all 4 spark plugs hopping that was the problem. It helped but i am still only averaging 42-43 mpg now. during this whole time my riding style hasn't changed, I still am almost always under 6K rpms and fairly easy on the acceleration. they bike has 47K miles on it.
Anybody know why it may still be so low and what i can do to get it back up?
Any help is appreciated
 

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Not sure what your location is, but the two biggest things that affect your mileage in winter is the cold temps increase friction in the crankcase and wheel bearings, plus the winter-blend gas typically drops MPG about 3-5% over summer blend. Should see lower MPG in your car as well.
 

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Discussion Starter #5
I am using the odometer, but when calculating the mpg previously i also used the odometer. so the percentage difference would stay the same, verse using gps or odometer miles
 

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I am using the odometer, but when calculating the mpg previously i also used the odometer. so the percentage difference would stay the same, verse using gps or odometer miles
What I was getting at is the odometer will be off when changing the sprockets. Unless the bike is using a sensor on the wheel.
 

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What I was getting at is the odometer will be off when changing the sprockets. Unless the bike is using a sensor on the wheel.
That is true if you change the size of sprockets, but I kept the same amount of teeth. So unless i misunderstood what you meant that wont apply to my bike
 

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I have been averaging about 40 mpg on my 2011 vstrom 650. About 6 months ago i was getting 48-52 mpg. I changed my chain and sprockets, air filter and all 4 spark plugs hoping that was the problem. It helped but I am still only averaging 42-43 mpg now. during this whole time my riding style hasn't changed, I still am almost always under 6K rpms and fairly easy on the acceleration. they bike has 47K miles on it.
It sounds to me like something is wrong with the bike with such a sudden and significant drop in MPG, assuming all parameters (riding style, gas, use case, etc) are the same.

Anybody know why it may still be so low and what i can do to get it back up? Any help is appreciated
FYI, Gen1 Wee has the speedo sensor built into the front wheel hub so this is not due to change in sprockets.

Here are a few things off the top of my head;
  • Ethanol Gas?: Perhaps the gas station you normally use switched from E0 to E10 or E10 to E15 (E=ethanol & 0,10,15=%). Ethanol does not have as much specific energy as gasoline so it does lower gas mileage. In the SF Bay Area I cannot get non-ethanol fuel (E0) but I'd think in Fresno it is probably available (more farming communities than urban). Find out if your station recently switch blends and/or find stations that you know have pure gas.
  • Dragging brake?: This can happen with the rear brake sometimes. It doesn't hurt to check.
  • Wheel bearings due?: If the wheel bearings have never been replaced they may be due and starting to drag.
  • Leaky fuel injectors?: The fuel injectors can get deposits that hang them up from fully closing (thus leaking) or fully atomizing the fuel which makes for an inefficient burn thus lower MPG. Run some seafoam or other injector cleaning additive and see if it helps or have your injectors serviced. RC Fuel Injection.
  • Weak Fuel Flow or Pressure?: A weak fuel pump or plugged intake sock or plugged high pressure filter can have a similar effect as a plugged injector. Without proper flow and pressure from the fuel pump injectors dribble instead of spray impacting a clean burn.
  • Bad Battery?: It might seem odd to blame the battery but a bad battery can have all sorts of weird effects. If it is anywhere near 4-5 years old just replace it before it strands you and rule it out as a cause. Test the whole charging system while you are at it, especially the ground wire to the motor.
  • Vacuum Leak?: At 9 years old and almost 50K miles the vacuum hoses and connectors are dried out, brittle and prone to leak.
 

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Are your spark plugs dark brown, black, or sooty looking? If so your bike is running rich. Check after driving with a warm engine and somewhat spirited, at higher revs, which should normally make them light sand brown or grey. You already made sure there is enough air, something is giving it too much fuel.
 

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Discussion Starter #13
dmfdmf, as far as drag from rear brake or bearings, I doubt it. The rear wheel and front wheel both free spin fairly well (now that I have the new chain on). The battery is still in good condition, and charging system is working. I have no clue how to test vacuum leak or weak fuel pressure. For the gas grade I’m not sure, but I wonder if the switches to a winter blend (someone else mentioned to be) and that if they did I may lose up to 10% efficiency which does correlate. 10% of 50 is 5 subtracted from 48 puts me at 43 mpg if that’s the case.
 

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That spark plugs look fine to me, others may have to chime in on this. How cold is it where you are/ where are you located? Do you have a short or long commute?

As for testing fuel pressure it is a tool you can rent from most auto part stores (NAPA, CT, Part source ect.) It is quite easy to do. Just add it inline to the fuel line running to your injectors, once hooked up the gauge should show you your real world fuel pressure.
 

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Discussion Starter #16
As far as temperatures it varies from 40f to 60f. My commute is 30 miles and about 30 minutes. I am in the CA Central Valley
 

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My current ride is an '01 carbureted SV650. I live at sea level on Long Island NY. Last summer I was getting (as always, calculated with odometer reading at fill up) 45 MPG consistently. Beginning in October/November I struggled to get 40 MPG. Beginning in May/June I am right back up to 45. Since '02 my rides have included a couple of Triumphs....a Ducati...a different SV...a gen 1 Wee (some carbureted, some fuel injected and all mechanically pretty perfect), the seasonal MPG differential in all the bikes remained proportionally very consistent. I don't know how they seasonally blend the OP's fuel in Fresno but I would suggest that the differential is due to seasonal fuel blending. Maybe the OP could chime in and tell us what mileage he is getting now, three months past March.
 

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Concur on the winter blend fuel.

I would bet that there is milage drop in your other vehicles in the winter as well, Even in central CA. they will put in additives that raise the volatility (lower the vaporizing temp) of the fuel for easier starting and less time running rich; "choke on" while it warms to operating temp. Here, where the cows outnumber the people, I have good availability of 91-93 octane E0 (no alchohol) premium- good for 3-4mpg and noticeable performance improvement over 87oct E10 on my '17 DL650. BTW NEVER put E15 or E85 in any powersports or small engine incl motorcycles, outboards, lawnmowers, etc.
 

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Here is what a fuel pressure tester looks like. I picked this up for about 40$
Please refrain from posting arcane tools, especially ones that are reasonably priced. It causes knee-jerk, compulsory purchases for us tool junkies that buy tools that will be used once or even never. :wink2:
 
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