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Thread: Fuel Consumption

  1. #21
    Senior Member DieselKrampus's Avatar
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    Jul 2016
    Quote Originally Posted by Polish View Post
    Compression is 140 psi with a Canadian Tire gauge. So......
    If that is an accurate compression reading, then there's your problem right there. Healthy compression is about 180psi. 140 is way too low for the engine to be running with any kind of efficiency.

    I would do another compression test with a proper compression tester, and using the specified method to make sure you get an accurate reading. If it reads around 140psi after that, then it's time for an engine rebuild.

    Just my $0.02

    Sent from my One X using Tapatalk

  2. #22
    Sensei 66Sprint's Avatar
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    Sep 2008
    Roanoke, Virginia
    Think of it this way...Atmospheric pressure at sea level is nominally 14.7 PSI ...If the cylinder (piston at BDC and still) was simply sitting with a valve open it would also be at 14.7 PSI...
    Turning the crankshaft SLOWLY to TDC only ONE TIME would yield a "dome" pressure of 132.3 PSI on a 9:1 compression ratio engine, 139.65 @9.5:1, or 147.0 on a 10:1 ratio cylinder.....
    However, rapidly rotating the engine adds two additional forces.....The exhausted gas volume creates a vacuum (area of reduced pressure) behind it, and the momentum of the incoming volume drawn by that and the vacuum created as the piston descends tend to slightly "overfill" the space creating a slightly higher starting pressure than atmospheric.....Then the piston compresses that up into the dome...How much and how fast it "overfills" are dependent on valve open duration, valve overlap, flow efficiency/speed through restrictions (carb and ports) and ring seal.......
    Any time your engine produces pressures at or below ONLY compression ratio times local atmospheric it NEEDS attention.......Something is amiss.......JMHO
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."
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  3. #23
    Super Moderator longdistancerider's Avatar
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    Oct 2011
    Vancouver Washington (text 408-239-9580)
    Quote Originally Posted by Polish View Post
    It runs awesome! I think my problem is assuming I used 13 liters for the mileage.....Next time I will take note of the liters I put in and calculate the fuel consumption accordingly.

    Also, the FSM says fuel capacity is 13 liters and fuel reserve capacity is 3 liters. So, is it total 13 with the reserve or 13 + 3 for a total of 16?

    I don't see why the fuel consumption would be so bad if EVERYTHING is stock and have been replace. You name it, it's either new, painted or polished!
    Fuel capacity is 13 liters, minus the 3 liters in reserve gives you 10 liters.
    Remember the old line about "assume"? Assumption is the Mother of All F*** Ups.
    Polish likes this.
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  5. #24
    Senior Member jseconds77's Avatar
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    Apr 2011
    jumping in real quick....
    so Kawi says my W650 is a 4 gallon tank but I dunno how true. I monitor with the handy digital trip meter and better get gas now range is 150 mi. as a rule of thumb, I never let bikes get below half a tank anyways..I feel the reserve part of the tank is taller/bigger than 450s and comes up quicker. only ran it on reserve once.
    early testors stated it was 43 mpg but with more torque and a motor that works less to go quicker, ya think it should be more? based on my riding habits if I am real easy on the throttle I felt my best was 45mpg, no highway ridin'.....but I don't see many reports of how it fares mpg on that terrain.

    so....43-45 mpg for a mild-mannered(real nice, even torque spread, redlines at 8k) W650 good? I always run premium even though it can handle 87. I feel my ol' 450 got similar mileage.

    I recall one of you saying you got 55mpg highway on a 450 but I think it had different sprockets.

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