Fuel coming out of front carb intake(after engine rebuild)...

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by BLUE(UK), Apr 24, 2012.

  1. BLUE(UK)

    BLUE(UK) Long timer

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    Hi guys, I will give a quick sumary of what I have done to my bike and how it has behaved after such works and will be needing info if possible because something is NOT right!!:huh

    Shipped bike to USA to do TAT,went great,loved it etc but last day lost 6th gear,no big deal.
    Shipped back,engine rebuild to replace shift drum.
    Tested bike,ran lovely but had a stumble at 2k revs and 4.5k revs.
    Cleaned carbs,changed plugs,changed plug caps etc but no joy.
    Got my second set of carbs and got them ultrasonic cleaned to clear immulsion tubes so as to not have the same problems. Built carbs back up(jets etc),put them on the bike,checking TPS etc on build up.
    Front carb was spitting fuel up from intake(seems to be blowing instead of sucking) but balanced the carbs til it stopped and seemed ok.
    Built up rest of bike and it ran good for about 5miles.
    Stopped at my brothers to say hello,tried to start,wouldn't start without throttle,ran like SHIT back home(1mile).
    Stripped it,spitting fuel on front intake again so stripped carbs checking all jets are correctly built,double checked air screw,TPS,etc,etc.

    Something else I noticed was that the front cylinder pipe doesn't seem very warm.....bloody odd!!

    Any idea's??

    It's probably something real simple but i sure cannot find it.

    Thanks in advance.....just gonna go lift some heavy weights 'cos i am severely hacked off!!!:deal

    Thanks in advance.
    #1
  2. Peanuts

    Peanuts Long timer

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    Check the cam timing?
    #2
  3. BLUE(UK)

    BLUE(UK) Long timer

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    But it ran fine with the other carbs besides the hestitant spots at 2 and 4.5k revs which I rode it like that for maybe 500miles since it wasn't unrideable, just not 'right'.
    It does seem like a timing problem but odd that it ran prior to the carb change.

    Still timing?
    #3
  4. TcRulz

    TcRulz Been here awhile

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    I had a similar problem and it ended up being valve adjustment. Here is a couple of threads I've contributed to that may help.

    http://advrider.com/forums/showthread.php?t=784773 and http://advrider.com/forums/showthread.php?t=781314

    I can't figure out why just changing the carbs would make this difference. Can you put the old carbs back on and see if it fixes the problem? Can you put your hand over the end of the muffler and feel a miss? Still sounds like your valves aren't fully closing or closing at the wrong time:eek1.
    #4
  5. Peanuts

    Peanuts Long timer

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    Ah, you rode it for a while with the other carbs, I did not get that, sorry.
    #5
  6. BLUE(UK)

    BLUE(UK) Long timer

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    Cheers for the replies so far. I've an evening off from training today so will double check valve clearances after work.
    It's still odd that it has gone from a 'stumble' at 2k and 4.5k revs to no power/spitting fuel out of front cylinder from just a carb change.
    It does make sense that the valves aren't on time or clearances are wrong but because I've not fiddled with them, I have hoped not.
    I'll check later and thanks so far.

    Anymore ideas?
    #6
  7. Monty_Burns

    Monty_Burns Excellent.

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    I thought you just rebuilt the motor? Didn't tear into the top end?

    I think the timing on your cams is not matched correctly to the crank. I screwed this up once and it was pumping air and fuel out of the forward carb. I was confused by the order of the photos the HOW. The service manual made more sense to my engineer's brain.
    #7
  8. BLUE(UK)

    BLUE(UK) Long timer

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    Rebuilt the engine, did approx 500miles afterwards with a stumble at 2 & 4.5k revs because it wasn't that bad to ride and I'd been over my work and cleaned carbs out many times so left as is.
    Last weekend I decided to 'fix it' by getting my spare carbs ultrasonically cleaned and built up. Front carb was spraying fuel out of trumpets so balanced til it stopped and gauges seemed balanced. I rode it for about 5miles in which it seemed perfect.
    Stopped at my brothers and upon restart the problems appeared but with no power. Since then I've found the front pipe doesn't even get hot.

    Hope that clears up more( I'm using the phone because I'm at work)
    #8
  9. adiablolex

    adiablolex Lost again

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    front pipe not getting hot means no fire, check your coil and connections to it, if everything checks out and the plug is good it should fire.
    If you have spark but still flooding the front cylinder I'd start looking at float height and check valve, there's a good possibility that if you're dumping fuel in there by the ton that the plug can't keep up thus the no ignition situation

    good luck with it man
    #9
  10. BLUE(UK)

    BLUE(UK) Long timer

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    After many hours working on it I've found the problem and I honestly feel like giving up....the deeper into the engine I dare go, the worse it gets!!!
    It's all of my own doing really because during the carb swap(I assume), a small screw(I've yet to find from where), has fallen into the inlet port which I can only guess got between a valve and held it open after my test ride(at my brothers) which is why it struggled to start/ran like shit.
    Do I feel pissed off??!!
    The valves are still sealing(petrol in the inlets to test and it holds) but checking the clearances, there is none at all so I'm guessing I've burnt the valves out but the head is ok. The only way I can get feeler gauges in the gap is to take the shim out completely. Let me know if you think I'm missing something here. I'm not a mechanic(obviously) but I give it a go.
    I'm going to whip the head off over the weekend and take a look and if no head damage, I'll replace the valves(just inlets since exhaust valves are sound).
    If the head is knackered, I'll take the head off my spare engine to replace it with.
    If you think my plans/ideas are wrong, let me know.
    Cheers for any Advice guys.
    #10
  11. Sumi

    Sumi Long timer

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    Have you actually found the screw, or did it make its way into the cylinder?
    #11
  12. BLUE(UK)

    BLUE(UK) Long timer

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    It was still in the intake port behind the valve stem, took some getting out!!
    I don't think it's done bore/piston damage but if it has I'll just put the cylinder on it from my other engine since the head will be off.
    #12
  13. Gustavo.Ramos

    Gustavo.Ramos Long timer

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    Pictures, always take picture, so we can learn how simple things can mess up with our head!

    Sorry, not much of a contribution, slow morning today..

    :D
    #13
  14. Sumi

    Sumi Long timer

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    Yeah, it would be great to see some pictures, especially of the screw - to find out where it has come from..
    #14
  15. BLUE(UK)

    BLUE(UK) Long timer

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    I know where it's from...the cubby box. The bolts that mount it to the frame I've always left them intact since the plastic holds them and it's removed before the airbox so never had a problem before.
    Like I said before, it's my doing/mistake....a big one at that!!
    #15
  16. BLUE(UK)

    BLUE(UK) Long timer

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    [​IMG]
    #16
  17. AdvGa

    AdvGa Long timer

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    Sorry to hear this little thing (with big results) had to happen to you.

    Thanks for sharing your findings and this just reconfrims to us who work on our bikes.... keep those holes covered at all times.

    May the Force Be With You!
    #17
  18. BLUE(UK)

    BLUE(UK) Long timer

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    No need to thank me, I've used the forum to gain a lot of knowlege and confidence so happy to try and put something back in(how NOT to do it in this case!!)
    #18
  19. BLUE(UK)

    BLUE(UK) Long timer

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    Finally riding like I stole it!!

    Just gonna put a few more miles on the rear wheel.....!!!
    #19
  20. Peanuts

    Peanuts Long timer

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    I'm glad you got it sorted. It's done nothing but rain whilst it's been in the garage so you have not missed much good riding ;)

    Strange how the clearance got tight.... have you taken the valves out of the head yet?
    #20