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1984 XJ750 hard to start and only runs on choke

Discussion in 'XJ Technical Chat' started by maxsauve, Mar 16, 2020.

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  1. maxsauve

    maxsauve New Member

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    Hey guys! So I just cleaned up the carbs from my xj750 (pine-sol, compressed air everywhere, the whole thing) and its acting up on me. This is the situation currently:

    Everything is hooked up EXCEPT the airbox, its physically their but not coupled with the carbs. Fuel tank is installed with gravity petcock to ON. Battery as juice also.

    Key on, choke off, crank and all it does is spin, no fire.

    Key on, choke on, crank and still only cranking, no fire.

    Key on, choke on, hand on the intake side of the 2 of the carbs (that's all I could cover with my hand), starts up and revs way up. If I remove the ckoke, it won't idle and would just die. After a couple of tries, I can start the bike without my hand in front of the intake side of the carbs (once hot) but it would only run with the choke ON. I can control the revs with the choke lever also.

    So I know I have spark on all cylinders, compression is ok , valves have been checked. It's clearly a carb problem...

    I've wet set each carb, bench synced, changed the throttle shaft seals for new ones, every jet where cleaned.

    ALSO, when I got the bike (last summer) it would start immediately and idle OK, but rpm's would either rise up or die (throttle shaft seals where completely eaten up, so I changed them).

    My questions: WHAT SHOULD I DO?

    - I've set my air/fuel mix screw 2.5 turns out, should I turn it more?
    - My do I need to add back pressure with my hand to start when cold, but once it gets hot I don't really need to? And it only start with the choke ON.
    - Should the butterfly's be fully closed on idle? Or have a little seem of light?
    - Could it be a petcock issue? It's a gravity feed one and I had fuel in each bowl.
    - Pilote circuit clogged? How can I extra clean that sucka?

    Thanks for your help

    ** Also I know it's not a choke but more an enricher, it's for the sake of simplicity I call it a choke. Thank you!
     
  2. jayrodoh

    jayrodoh YimYam Premium Member

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    Pilot circuits can be a bugger to clean properly.

    Have you checked the intakes for vacuum leaks? Vac leaks can cause all the problems you are describing.

    did you set your fuel levels? Too low and it’ll be a lean mix.
     

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