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Tuning '85 XJ700n

Discussion in 'XJ Technical Chat' started by Tom1969, Jul 23, 2014.

  1. Tom1969

    Tom1969 New Member

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    I recently brought the valves into spec, did a thorough "Church of Clean" cleaning of carbs using all the suggested replacement parts from XJ Forever. I used a Colortune to get the plugs blue and then synchronized the carbs with a Carb Tune and proper YICS tool. I got it singing pretty sweet. Quite proud after my third time through the carbs.

    Here is the problem. I disconnected motor from makeshift fuel supply - folgers can and gas line with a ball valve. I hooked up the Bike's fuel tank with both vaccum and fuel lines and now I am getting some back firing and hesitation when I rev the engine up to 3k.

    Suggestions? Or can you point me to a step-by-step tuning procedure, similar to that of rebuilding the carbs?

    Thanks
     
    Tom1969, Jul 23, 2014
    #1
  2. paul.hardy

    paul.hardy Member

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    Did you try running it on prime could be an issue with the Petcock
     
    paul.hardy, Jul 23, 2014
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  3. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Did you use a coffee filter?

    dave
     
    hogfiddles, Jul 23, 2014
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  4. SLKid

    SLKid Active Member

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    Is it sputtering and dying too?
    Dirty gas cap maybe, not venting??
     
    SLKid, Jul 23, 2014
    #4
  5. peganit2

    peganit2 Member

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    A classic sympton of caffeine withdrawal. 8O
     
    peganit2, Jul 23, 2014
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  6. Tom1969

    Tom1969 New Member

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    Thanks for the tips, will give it a try tonight and see if it is a petcock or cap venting problem.

    And yes of course I used a filter, I never slow drip without one. It's the swede in me.
     
    Tom1969, Jul 23, 2014
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  7. Tom1969

    Tom1969 New Member

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    I tried the venting with the cap first and it made no change in the engine performance.
    Ok, switched the petcock to prime and it ran some better. Took it out and rode it hard and it still has a dead spot - power loss - between 2700 and 4000 rpm. But it picks up after that. Obviously petcock?

    Good to the last drop brothers.

    Let me know what you think.
     
    Tom1969, Jul 23, 2014
    #7
  8. Tom1969

    Tom1969 New Member

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    Whoopty do! located the gremlins in the those Hitachis. The plastic caps on two of the needle jets were on upside down, not allowing the needle jets to move up and down easily.

    Also found o ring caught in spring of fuel mixture screw.

    Fixed both and Im colortuned, synced and running. When I bought the bike for 200 I did not realize I was going to have to perform this kind of excorcism. Blessed the house with gasoline and Im going to bed.
     
    Tom1969, Jul 27, 2014
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  9. Tom1969

    Tom1969 New Member

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    Whoopty do! located the gremlins in the those Hitachis. The plastic caps on two of the needle jets were on upside down, not allowing the needle jets to move up and down easily.

    Also found o ring caught in spring of fuel mixture screw.

    Fixed both and Im colortuned, synced and running. When I bought the bike for 200 I did not realize I was going to have to perform this kind of excorcism. Blessed the house with gasoline and Im going to bed.
     
    Tom1969, Jul 27, 2014
    #9
  10. Tom1969

    Tom1969 New Member

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    Whoopty do! located the gremlins in the those Hitachis. The plastic caps on two of the needle jets were on upside down, not allowing the needle jets to move up and down easily.

    Also found o ring caught in spring of fuel mixture screw.

    Fixed both and Im colortuned, synced and running. When I bought the bike for 200 I did not realize I was going to have to perform this kind of excorcism. Blessed the house with gasoline and Im going to bed.
     
    Tom1969, Jul 27, 2014
    #10

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