The issues of fuel injectors and "adventure" bikes

Discussion in 'The Perfect Line and Other Riding Myths' started by Mambo Dave, Jan 10, 2013.

  1. slartidbartfast

    slartidbartfast Love those blue pipes

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    This is the second time in recent weeks I have heard that carbs are preferred by KTM in the Dakar rally because of fuel problems. I find it strange as I would expect that any entrant who has the funding and abilities to compete in the Dakar would easily be able to ensure they were filling up with clean gas. Still, if that is really a problem I'm not sure that changing an external fuel filter or an injector would take very long if they were designed for quick changing. I suspect there may be another reason that KTM doesn't want us to know about and fuel cleanliness is just the excuse. Maybe their fuel pumps burn up when fuel is sloshing back and forth for hours on end introducing bubbles ... IDK

    For an adventure bike both systems have their merits. A carburetor is undoubtedly easier to work on by the side of the road and arguably has fewer parts to fail. I suppose you could carry a complete spare carb with you, quite easily if you wanted to. However, modern FI systems are extremely reliable, deal with large temperature and altitude differences more effectively and can still be serviced and maintained fairly easily by someone who knows what they are doing. Furthermore, you are likely to get better fuel efficiency from FI and I for one, would trade the few extra miles per tank for any theoretical shade-tree wrenching advantages. I have never had any trouble from the FI systems on my current so-equipped bikes but can think of several times when carbureted systems have had problems of one sort or another (fuel leaks, stalling, poor running, etc. - even leading to a holed piston one time.) This has especially been the case when a bike has sat unused for any length of time.

    I really don't understand the strong opinions held by some people on this topic. I'm not going to let the fuel delivery system on a bike influence my choice of purchase (unless that particular implementation has a known issue) and I'm not going to sweat about whatever the manufacturer has seen fit to install. If I take my DR350 up into the Rockies to ride some of the high passes (which I hope to do some day), I suppose I will revert to the CV carb and/or take a supply of jets with me. That might be a small hassle but the bike is old, cheap and will run without a battery if necessary so it's a reasonable trade-off (yes I know there are some battery-less FI bikes now.)
    #21
  2. larryboy

    larryboy Chopper Rider

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    Oh, I thought the title of the thread was "adventure bikes"...I must have missed the hijack. :lol3

    I've never even heard of a failed carb. Failed fuel pumps, clogged screens and stuck injectors, fubar'd TPS', yes.
    #22
  3. Jnich77

    Jnich77 Been here awhile

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    Exactly!!!! Not like they take up a lot of room....lol.
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  4. PeterW

    PeterW Long timer

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    I've had more problems with carbs that FI in all the bikes I've owned, including dirt in the jets. Far less tolerant of water as well - so far the FI has been faultless.

    Agreed, something like the Dakar is the extreme end, most of the problems have been fuel pumps though, not the actual FI. If you are going to have five fuel tanks, the complexity of moving fuel around is likely to screw you up, carbs OR FI.


    Pete
    #24
  5. syaufu

    syaufu Been here awhile

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    Rode London to Bejing..Injected bike..bad fuel ..17,000 ft ..no problems...Lady with Carbed bike..in van above 14000 ft and worked on carb and jets almost every nite when in the high altitude of Tibet trying to get bike to run properly...not a mechanic..just a rider but I will take an injected bike any day after that experience..bj
    #25
  6. ttpete

    ttpete Rectum Non Bustibus

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    In-tank pumps will live a long time as long as the fuel level is kept up. The pump depends on fuel to cool and lubricate it, and low fuel levels will kill it in short order.
    #26
  7. JimVonBaden

    JimVonBaden "Cool" Aid!

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    That's a bit of a stretch. Though fuel does cool the pump, running low on fuel will not cause a pump to fail in "short order"! The cooling comes from fuel going through it far more than around it.:deal

    Jim :brow
    #27
  8. ttpete

    ttpete Rectum Non Bustibus

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    Bear in mind that fuel is continuously recirculated through the pressure regulator, and that last pint can get pretty warm. Even though the pump section may be cooled, if there's a deep enough sump the motor bearings can run without fuel to lubricate them once the level drops enough.
    #28
  9. fast4d

    fast4d Long timer

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    most newer EFI systems run 'returnless'. there's no circulation of fuel

    I would think the returnless pumps are cycled and don't run constantly on the same intensity therefore eliminating overheat conditions.
    #29
  10. VxZeroKnots

    VxZeroKnots Long timer

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    At least on the Husky I have this is true.
    #30
  11. Warin

    Warin Retired

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    If you have 5 fuel tanks you are going to have fuel pumps, EFI or carby!

    EFI fuel pumps use the fuel flowing through them to cool themselves, they are about 60 watts (when running all the time) so need some cooling. Some EFI pumps are mounted outside the fuel tank and are about the same size as the ones mounted inside the fuel tank! So it is the fuel inside the pump that does most of the cooling (given air has less cooling effect). More modern systems don't run the pump flat out all the time thus reducing the heat (and electrical) load. EFI pumps are fairly reliable, more so than the carby fuel pumps usually fitted to some bikes ... If I had a bike with a carby fuel pump I'd be servicing it every other time I'd change spark plugs.
    #31
  12. ttpete

    ttpete Rectum Non Bustibus

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    I changed a lot of pumps on pickups with two tanks. They wouldn't switch tanks until one ran dry, and that killed the pumps.
    #32
  13. Aussijussi

    Aussijussi Long timer

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    I wonder if the KTM have FI sorted out on the new 1190ADV, getting rid of the unsteady running that occurs around 4000rpm, other than that, i've had no FI foes on my 990 adv, in the six years that i've had it.
    #33
  14. hugemoth

    hugemoth Long timer

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    I do a lot of off road riding alone in remote locations so it's defiantly carbs for me. I'm a mechanic. I do understand fuel injection systems, I do understand carbs. I like a simple carbed bike that will run without a battery.
    #34
  15. abhibeckert

    abhibeckert Long timer

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    Conditions at dakar are a lot harsher than anything a typical adventure rider would face. I dunno about you, but I find riding in someone's dust cloud even more stupid than riding at night. Especially since (at least where I live) you are likely to see cattle or horses and definitely kangaroos on any dirt road. I've had a few near death experiences even when I can see clearly.

    Long before there's enough dust to get through the fuel cap breather hose into the fuel (how else does it get into the injector?), I'm gonna pull over and wait until the dust clears.

    If an engine failure is "close to a life or death factor" then you're doing something wrong. There is a long list of parts that can fail, no amount of precautions can guarantee you are going to get where you're going.

    The biggest benefit for me is fuel efficiency. My 645cc fuel injected thumper is slightly more economical than the 250cc carb'd thumper it replaced, and a *lot* more fuel efficient than my dad's 650cc carb'd bike. My fuel tank is a lot lighter than his and I get further on a tank. Plus I have ~30% more power according to the dyno charts I've seen (obviously that's not because of the injector... but it is impressive when you compare fuel efficiency, especially since his transalp has fairing and my 690E does not).

    I'm not fussed about what's probably a negligible power gain, but the extra fuel range and smaller tank really is a big deal. I could fit a carb if I wanted, but I choose not to. Perhaps riding in a country with dodgy fuel I might change my mind.

    I'm approaching 50,000km now and have had no fuel issues, except one time when a badly routed fuel hose started leaking after rubbing on a bolt (good old electrical tape got me home).
    #35
  16. DepthFinder

    DepthFinder Portly Adventurer

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    Returnless simply means that the regulator is at or in the pump assembly. These systems will run a set pressure and modulate the IDC to account for changes in manifold pressure. I've never seen a pump that cycles (although many autos use voltage modulation to the pump to keep it quiet at low load and prevent regulator overrun at low IDC)

    edit to add: There are also semi-returnless designs (such as BMW auto) where the fixed pressure regulator is contained in the external fuel filter with output to the engine and return from filter to tank.
    #36
  17. fast4d

    fast4d Long timer

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    that explains the $100 fuel filter I bought.:eek1
    #37
  18. ADW

    ADW 'tard bike restos

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    Yep. Like my buddy's F800GS last year that the battery died and, guess what, no power = no EFI. Dead on the road. The other two of us on the trip rode 1.5 hours to the nearest town that luckily had a NAPA store with a battery close enough to fit the GS.

    This experience was quite unlike my other buddy's KLR that we bump started and continued to ride when his battery wouldn't restart him on the road on a different trip.

    Carbs are easy to clean in the field, and require no computer or battery power to operate. Both EFI and carbs don't like dirt, but since I don't need electricity to run my carb, that's 50% less failure mode to worry about. Better for bad conditions in my opinion. I recognize the power and fuel economy advantages of FI, but the simplicity and ability to deal with it on the side of the trail drove me to pick a carbureted ADV bike.
    #38
  19. bobnoxious67

    bobnoxious67 Baby steps...

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    Nope. "returnless" just means the fuel pressure regulator is in the tank...there is constant circulation, but it's inside the tank.

    DepthFinder has it right:deal

    #39
  20. Tepi

    Tepi Been here awhile

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    Unless you have magneto ignition on your bike, you're going to need power/battery for ignition. Therefor carbed bikes WILL need a source of power, so if your magneto/alternator dies and your battery runs out, you're still shit out of luck. Might wanna find a diesel bike, they should basically run without power if you get them started.
    #40