Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Why does the CB250 have better fuel economy than the VT250 Spada

Discussion in 'Bike Reviews, Questions and Suggestions' started by jaguarfanster, Feb 9, 2012.

  1. Hey all,

    Did a bit of reading around the webs and I've found that most cb250 riders get

    around 3.5 to 4 L/100. Conversely the VT250 Spada riders, like myself, get only

    around a max of 5 L/100. Now both of these bikes have exactly the same

    displacement, and cylinder number. However the Spada adopts the V-twin

    configuration whilst the CB250 has the parallel twin. Does this alone explain the

    variation in fuel economy, or am I missing something here?
  2. The VT250 makes more power, it takes fuel burnt to make power. Other things being equal a bike with more power and similar weight will use more fuel.
  3. All sorts of things affect fuel burn. My Versys (650cc parallel twin) uses between 4 and 4.8 l/100km (as low as 3.9 and as high as 5.1) and puts out 60hp. Fuel injection buys you a few percentage points...
  4. Try compaing the mass weight, bore and stroke, gearbox ratios, sprocket ratios, exhaust size and back pressure, valve size both intake and exhaust, camshaft lobes, and assuming they both have carbies compare carby size, carby needle size, needle height settings, jet size and fuel / air mix just to name a few.
  5. Also riding style, how gentle or aggressive on the throttle, heck, even the weight of the rider, quite honestly, ive been bikeless for nearly a year now, a cb250 would be like heaven right now.
  6. aerodynamics, wind direction, tyre pressure, type of tyre, road condition and inclination............ just to name a few more. Lets see how long we can make the list
  7. These things?
    Last one I had a look at only had the one carb feeding the two cylinders, and assuming the spada has two, I would say that's the big factor. Also ill bet the cb is tuned for economy and the spada for power/performance.
  8. last one i saw looked like it would only be running on one cylinder:p
    that would explain it:)
  9. yeah good points i suppose....especially with the single carb....maybe some carb rejetting could get my spada drinking less power/performance is not really my aim with a 250 haha
  10. Some smaller jets maybe then. I recon you would have to be careful you don't go to lean though, might damage the engine. And messing around with jetting can get expansive and very time consuming. V-twins are even more fun, the different cylinders usually have different jetting, the rear cylinder doesn't get as much cooling, runs a bit hotter... Not sure if it's so much of a problem with water cooled engines though?
  11. Just leave it alone it's a 250
    • Like Like x 1
  12. If your worried about how much fuel a 250 uses you really are a tight ass,and should be thinking about having more fun on your bike
    • Like Like x 1
  13. I am a tight ass. So what? I have fun taking my machinery to the limits of its engineering capabilities. By

    calculation of the molar enthalpy of petrol, combustion engines and traditional drive trains are only about

    1% efficient at the rear wheel. That basically leaves 99% of potential to exploit for power/performance

    fuel efficiency. Considering that that the Spada is "only a 250" that gives me a brilliant blank canvas to try

    out some of my techniques. After all if things go wrong I don't lose much. Anyway, currently I am building

    a cheap EFI conversion kit for my bike with the "ECU" taking the form of a 4th generation iPod touch.

    Let's encourage motorcycle research and development instead of suppressing it.
  14. I find your ideas intriguing and wish to subscribe to your magazine.
    • Like Like x 2
  15. I like your way of thinking but I also think your comparing apples to oranges.
    Yes they are both 250's but the way I look at them thats where the comparison stops

    CB250 single carb, air cooled, inline twin

    VT250Spada, twin carb,liquid cooled, V twin and dry weight is 10kgs heavier than the Spada

    So there is a very different torque curve and use of fuel to start with.

    My Older CBR1000 got on average 7 to 10ltrs per 100 depending on the ride.
    Constantly got over 300ks range with a 22ltr tank
    My VTR1000 gets 12/100 on cruising and 10/100 or less when 'playing"
    I have never got over a range of 150ks ( with the red you need fuel NOW light on ) out of a 17ltr tank
    Yes the twin uses LESS fuel when opening the throttle and letting it breath better, thus a more efficient fuel burn.
    Both bikes had/have engine/exhaust mods etc.

    Ps ... I dont give 2 ratz about fuel usage just how much fun the usage gives me ... prob why my cage is a 5.7ltr toy as well :angel:
  16. Likewise. Particularly the stuff about the custom ECU.. sounds like a dream project to me.
  17. I suspect much of the difference is actually down to the gearbox. When I ride my daughter's spada, It's generally pulling 7-8K rpm. I suspect a CB would be running 5-6K rpm at the same sort of speeds (with correspondingly slower acceleration).

    If you want to improve the fuel efficiency of a spada, you could just put a smaller rear sprocket on it.