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Tuning help

Discussion in 'XJ Technical Chat' started by kmattinson, Jul 21, 2012.

  1. kmattinson

    kmattinson New Member

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    I just purchased a 1985 xj700 maxim. I have cleaned out the carbs, tank, and was able to get it running decent. But once in a while it starts to run like crap and leaves me stranded. I have done a lot of reading tonight and might have some ideas to what is causing the problems I am having. Mainly it starts to bog out and surge when accelerating at lower rpms, but at higher rpms, 5,000 or more, it is fine. Number one cylinder also seems like it is running rich since the plug is black, and it is making what seems to be a valve train noise. kind of like a fast ticking noise, it mainly does this once it is warmed up.

    Here is my list of things I am going to try to get to this weekend.
    1. Adjust floats to 17.5 mm, then check with clear tube method that they are 3mm below gasket surface.
    notes: I recently adjusted them to 16 mm, but obviously this is wrong

    2. Adjust pilot air mixture screw, starting at 2.75 turns out
    Notes: when cleaning the carbs they were at 1.5 turns out so I put them back to 1.5 turns. Guessing this is wrong. Also is there suppose to be an O-ring in there? on some I was able to get the washer out after i removed the spring, but never saw an o-ring.

    3. Adjust the valves so there within spec.
    Notes: I checked the clearance and there all a little tight. Ordered a tool, so after it comes I can remove the shims and order new ones. Where is the best cheapest place to get shims?

    4. Use the home made two bottle method to sync the carbs.
    Notes:already bench synced them. What is the yics I need to disconnect when syncing the carbs?

    Let me know if what I have said is right or not and if anyone suggests anything else I should check. So far I like the bike a lot when it is running decent, but I know it is way out of tune and has a lot more power left. All my friends have new 750 and 1000 cc's bullet bikes. I just want to be running good so I can pretend to be able to keep up with them.

    Thanks
     
  2. wizard

    wizard Active Member

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    Could be a bad plug & the ticking could be a leak on a header gasket.
     
  3. mtnbikecrazy55

    mtnbikecrazy55 Active Member

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    The ticking is normal on these engines. It's just the valves happily chattering away
     
  4. kmattinson

    kmattinson New Member

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    Yah the normal ticking is, but once my bike warms up it develops a different ticking, and it is only coming from the front left side. Doesn't seem like an exhaust leak though, I checked all the header bolts and didn't have to tighten them much
     
  5. kmattinson

    kmattinson New Member

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    And on the bad plug, I switched number 1 and number 4 plugs around. (number one was the black one) then after driving it for a bit, the new plug that looked like it was burning good in cylinder 4 turned black in cylinder 1, and the old one I put in 4 started cleaning up. Might be a float problem, I need to check
     
  6. sofakingjm64

    sofakingjm64 Member

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    Ticking from just the left side? Maybe it's your petcock diaphragm ticking in and out. Mine does this from time to time, and usually when it warms up.
     
  7. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    GET A SERVICE MANUAL.

    Get the valves in spec; properly clean and service the carbs.

    REPLACE the exhaust header-to-head gaskets.

    If the bike is YICS-equipped, it will say YICS on it in a number of places. This is a passage that interconnects the intake tracts; it cannot be "disconnected" it needs to be blocked when you do your vacuum sync.
     
  8. kmattinson

    kmattinson New Member

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    Do you guys suggest any specific service manual to buy for my bike?
     

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