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carbs and exhaust backfiring, bike won't start

Discussion in 'XJ Technical Chat' started by Scottyb321 @gmail.com, May 12, 2015.

  1. Scottyb321 @gmail.com

    Scottyb321 @gmail.com Member

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    Location:
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    Hey guys!

    long story short I yanked the carbs to thoroughly clean them and had new components installed (Factory parts, no mods). unfortunately the bike still wont start and continues to backfire through the exhaust as well as the carburetor when trying to start it. I'm even seeing some pretty vicious flames coming from the exhaust! I haven't gotten it to start ever since. Just so you know, I was having the same problem earlier which is why I pulled the carbs to begin with.

    The only other issue I'm having is that no matter what position the petcock is in fuel never stops flowing. In others words I can't restrict or shut off the fuel flow (it's not overflowing). when I removed the vacuum line from the manifold and sucked on it no fuel came through.

    Because of this I don't believe the carbs are starving for fuel.

    Could it simply be that the air to fuel mixture screws need to be adjusted or does anyone have any other suggestions as to what the problem maybe? coils are good spark plugs are good plug wires are good...

    Any advice is appreciated!


    Thanks
     
    Scottyb321 @gmail.com, May 12, 2015
    #1
  2. pkay

    pkay Member

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    Location:
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    Hi Scotty
    I had a similar issue with my GPz750 when I was trying to get it running again. I bought an auxiliary fuel tank so I could check things were OK without the tank in the way ($12 of eBay). Bike ran fine o0n the Aux tank once I got everything lined up (carb bowls, cable tension, idle adjustment, mixture, cleaned the air cleaner (my Z1300 backfired like a pig because the air filter was clogged making it run rich), good battery, clean carbs, vacuum hose no leaks). And turned out the vacuum petcock was stuffed and also filled my crankcase with fuel overnight. Sounds like yours is already stuffed so put a new kit in and eliminate that. Then work through the other things - with the tank off you can se a lot more too. The Aux tank is the best $12 I've spent in a long time. I got told by an old school mechanic about 1.5 turns out from fully in is the starting point for mixture screws. Works well so far.....
    Good luck and good patience
     
    pkay, May 12, 2015
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