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A newish efi bike chewing fuel - any thoughts ?

Discussion in 'Technical and Troubleshooting Torque' started by bennjamin, May 18, 2010.

  1. Hey everyone , thought I'd just rattle some brains before I go back to the dealer.
    I have a new bike ( model not relevant ) , just on 3000ks on the clock.
    Something I've noticed - the bike is getting considerably bad fuel economy.
    From 14l it hits 180-200ks before hitting reserve.
    Other bike owners of the same model , similar ks and useage are getting some 300+ ks before hitting the same reserve.

    Noteably , my everyday use , ks rider weight and fuel use hasn't differed from the average use. I mean , I'm not up the putty road everyday or slung over sideways around Wakefield .

    My query is , what are peoples thoughts to what is causing this ? Sensor failure ? Bottom end / bad ring issue ?

    Paying $8000 for a almost new bike and been promised " a easy 350-400ks" from a tank is leaving a bad taste in my mouth, as I had ideas if some medium distance rides on her too.

    Btw I have started log books from the last two tanks , and are currently Getting around 7l/100ks compared to mid to high 4l/100ks it should be getting

    bah !
  2. for a 600-100 supersport I would have thought that 180-200k's from 14l was pretty average. It has been for me and my riding style over the last 8 years on the gixxers (600 and 2 1000's), but as your sig says cb400 then that is probably a bit high

    I've found that by using 6th gear on the freeways has taken my economy up to around 220-230k's on the 1000. Personally I don't like being in such high gear but budget has dictated to me that I need to do this now. It also makes a huge difference with stop/start traffic. Travelling from Ferntree Gully to Mulgrave was much worse economy than travelling from Ferntree Gully to the city where I get to use the freeway.

    It will take time to find your base and from there you need to try things to improve. I have had over 300 k's from the 1000 but that was on a far ride where I was doing 200-300k's in a stretch with very little stop and start riding.
  3. If it were a big twin, then that would OK. A Cb400 should be getting better than that, even if it is still running in. Take it back. There will be a hose loose or similar. Get a compression test if the problem persists and the dealer denies.
  4. My economy ranges from 5lt/100km to as high as 15lt/100km. How? It’s the way its been ridden and the environment on that particular day.
    I suggest if your CB400 starts hot and cold, idles correctly and revs freely there not much wrong with the EFI.
    You may also be complaining about excessive break pad wear too.
    I'll back its riding style and experience although you will use more fuel while running in it wont be a great difference.
  5. 7L/100 from a 400..

    Is that 200 kms short or longer journeys without stopping? If you're getting that economy when cruising and all on one tank, then I'd suspect an issue. Otherwise, if you're commuting in traffic and or short trips, the tank range isn't unforeseeable (but still pretty bad).
  6. 4L/100km no way unless its a 250Cc or under my 400cc bike does 6l/100 and with 1 Liter bikes - never owned one that does under 8L/100km

    What bike do you own?
    It it does burn a lot i look at the oxygen sensor. If faulty the ecu goes in safe mode (prevent detonation) and runs rich.. What fuel are you using 95 octane>

    aha a cb400 just noticed... Well maybe your carb air/fuel ratio nozzle is set for too rich.. Does it backfire sometimes?
    when was the last service done?
    If its strong on power whats the point of doing compression check on a low km bike.... ?
  7. I get about 6.5 out of the 955i whether I'm up it, in traffic or cruising (actually get about 6 cruising).

    So I'd say something is wrong if a new efi 400 can't even match that.

    If it were 25% down in compression on one cylinder you would be pushed noticing it from a performance point of view, particularly if it were your first and only bike.

    Not saying race out an do a compression check. just saying if Honda claim the EFI is right, then best to check the compression.
  8. appreciate all the thoughts - yes its a CB400 , EFI.

    I only start this thread , as its noticeably worse economy than other owners on this site. My riding weight and style is similar too ( mostly stop start morning then cruise home , around 40-50km per day ).

    Regardless , after reading about it and been told by dealers i just wouldnt think a new 400 would get 7l/100km average. thats what the new CBR1000RR gets afaik and its a weapon (unlike this chugbox lol )

    Perhaps the bike is stuck in cold idle ? (its got a ICAV ) Or doesnt warm up within my daily back and forth riding distance ? ( running rich constantly etc )
  9. In a 20-25 km trip you are probably spending 3-5km in "choke" mode and another 5 coming up to temp. So that isn't going to help your average. Still I think it's worth asking about.

    Go on a day trip and see how the economy goes.
  10. could very well explain the shitty fuel economy , ill try and stretch its legs more often and see if that helps.
  11. also never believe anyones economy

    ohh i get 2 weeks from a tank and only costs $7 to fill

    thats not real technical now is it

    others dont know how to do the math

    others do a holden, totally full tank cant possibly get another drop in it, then when refuelling shut it off at first click claim its full and calculate the numbers from that.....

    i'd try going on some longer rides and changing the fuel you use, try another servo/brand

    and just get the bike checked out to make sure there arent any codes etc...
  12. What does it smell like? If it is rich, your eyes will water.
  13. I'll chip in here with the cold start mode eating your fuel if you're only doing a short run. To put it into prospective my car will drink fuel at a rate of about 10l/100km on the highway when the engine is anywhere under 65.C roughly then will drop to 6.5l/100km once the engine is at operating temperature. It takes about 8 minutes to reach full operating temperature. So if it's a 20 minute trip and keep doing that I'm looking at using 8.5l / 100km vs low 6's if I drive the entire tank without going through a heat cycle.

    Make sense ?

    My bike on the other hand is a carburetor 2 stroke. It uses roughly the same fuel no matter what I do with it. It's 3.5l/100km or 3.5l/100km pretty much.

    You can believe my fuel economy numbers :) I make a point of measuring them as precisely as possible. I always fill to the top of the tank then compare the litres taken to fill against the distance travelled since the last refill.

    7l / 100km does sound very excessive for a very much non sports orientated bike though.
  14. Try letting the bike warm up fully in the garage before taking off in the morning. You can always tell when it's finished with its warmup/choke cycle as it'll enter a stable low-rev idle, and most bikes I've owned that takes 4 to 5 minutes. When it's warming up, the EFI engines tend to cycle up and down the revs a bit at about 1.5-2x the warm idle RPM's, and always seem to spew out a heavily rich exhaust mixture.

    Even then, on a 20km one-way trip, letting it fully warm up or no, a third of your trip.

    Also, even small variances in throttle application can affect your economy. For the first tank of fuel in my new 675, I was getting 4.8l/100kms during that initial first tank run-in. Second tank it dropped to about 5.5l/100kms, and pretty much ever since then it's sat at around 6.5l/100kms as I started to rev the engine more fully but even then, not fanging it. Running it hard in the hills it'll get down to 8l/100kms, and at the race-track it was all the way down to 10l/100kms.

    So yeah, a high revving 400cc bike that weighs a fair bit (and the CB400's do) that only travels 20-25kms at a time while its warming up, not even being ridden that hard at all, and I'm not that surprised it's down to 7L/100kms.
  15. I'd recommend not breathing while you're in there with it though. :grin:
  16. 7l/100 is shit for a 400 commuting. Especially a modern EFI bike. My carbied '93 VFR 400 will get between 200-260kms on 11 litres commuting easy and I am most certainly not gentle with the throttle, nor am I exactly lightweight. Something is out of whack. Faulty 02 sensor? Faulty temperature sensor? Crook thermostat? Just guessing.
  17. Yeah, but you live in Geelong (correct me if I'm wrong here). Not like Sydney peak hour where you're stop/start/idle every 500 meters.
  18. True, true. But the reason we ride bikes is so that we can lane split no? Thus negating stopping and idling every few metres.

    Although I must admit that when I did live in Melbourne my version of commuting was $1.40 up the emergency lane. Which I guess would even things up a bit. Ha ha ha ha.
  19. While true/possible in Melbourne, due to the fairly wide and generous streets, anywhere within about 20kms of the Sydney city center is about as generous for space as Toorak Rd with cars parked on both sides with their driver doors open, and a tram going down the middle. Heck, even the major roads all seem to be narrower up there.

    I last rode a bike through there in '97, and my thought at the time was that it was pretty terrible even for bikes to get through/around the congestion. We're 13 years on now.

    Besides, neither of us really know what this guy's riding style is like, but I'm guessing he's a fairly new rider and not ripping down the verges. Don't know. All I know is that Melbourne is a snap to get around on a bike in comparison to Sydney.
  20. My twofiddy only does about 180-220 kms before hitting reserve on a 12L tank. 180 being around town vs 220 highway. And I'm a good 10kg under average weight and am very gentle on the throttle, using 6th gear whenever I top 50km/h (just cuz I love the vtwin burble :p)

    Also with the warmup theory - as I've learnt at Tafe, sitting in the driveway idling for 10 minutes will warm up an engine about the same as driving casually down the road for less than a minute. It also uses more fuel and ruins the environment faster than a Toyota Prius can save it.
    I've also found that with my engine, it wont even consider firing below about 2-3C air temp, without full choke, but once im 10m out of my driveway I flick the choke off and a few hundred metres later it idles just like it would any other day. The thermostat stays shut, and thus the temp needle is stationary about 2 needlewidths left of the guage itself.. but oil temp is fine within a couple mins.