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Seems I have a problem with idle.

Discussion in 'XJ Technical Chat' started by JPaganel, Apr 4, 2013.

  1. JPaganel

    JPaganel Well-Known Member

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    So, the 750 that got me here.

    Braks rebuilt front and rear, carbs rebuilt, floats set, valves clearanced. Should need a sync and be good to go, right?

    So I build a synchronizer and go at it. Synched 1-2, then 3-4, then 1-2-3-4.

    And then it revs to 3000 all on it's own. And when it doesn't and runs at 100 or so, there is this clattering sound from the engine.

    The only thing I can think of is that the timing chain guide gave up the ghost and the chain is loose.

    What else could it be?

    This is disappointing enough to think about dumping this bike...
     
  2. adrian1

    adrian1 Active Member

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    Re: Seems I have a problem.

    probably just the cam chain slapping around with poor running/jerky engine. Your description of the problem was quite vague. Can you hit us again with a more detailled description of how its running/starting etc?
     
  3. MercuryMan

    MercuryMan Active Member

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    Re: Seems I have a problem.

    what do you mean runs at 100 or so? Do you mean 1000rpms?

    Are your vacuum rubber caps new? They can seem good but still leak and after getting pried off and on that might crop up. Drink a brew, sit it out for a bit. Whatever it is can't be that hard and can be solved.

    Also just to be clear, how was it running before the synch? Or do you just now have it back running after all the maintenance?
     
  4. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Re: Seems I have a problem.

    Probably a vacuum leak, either between an intake manifold and the head, or throttle shaft seals (unless you already replaced them.)

    Or you missed on either the sync or float levels.
     
  5. Special_edy

    Special_edy Member

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    Re: Seems I have a problem.

    Dont worry,
    The xj sound notoriously crappy and jerky when its running at a low rpm
    Im not sure if it has to do with the starter clutch or the transmission.

    try spraying starter fluid or better yet an unlit propane torch around the intake boots to check for a leak.

    Did you use the YICS tool when you synced and colortuned?
     
  6. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    Huh? :? are your carbs synced up properly?
     
  7. quebecois59

    quebecois59 Well-Known Member

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    Re: Seems I have a problem.

    Only time my Maxim-X ran crappy and jerky at idle was when the carbs were out of balance (out of synch).
     
  8. MercuryMan

    MercuryMan Active Member

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    Re: Seems I have a problem.

    I agree. My 550 when I first got it was noisy at idle-but after a valve adjustment, full carb clean, synch, once through the maintenance schedule and several oil changes with Q moto oil it now sounds like a well oiled machine even at idle. Of course it's not as quiet as a modern water cooled bike, but that would be scary if it was.

    In short the XJ's may produce more decibels of sound at idle than some other similar bikes, but they should sound rhythmic and healthy all the same.
     
  9. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    Sonofa...

    One of the rubber sections of the YICS tool was ripped up. I guess this makes the sync completely wrong.
     
  10. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    Yeah, would mean the valves were more than fag-paper tight :?

    And yep afraid it's true JPaganel, sync is likely out if the YICS tool wasn't sealing correctly. At least it's an easier fix than a timing chain :)
     
  11. quebecois59

    quebecois59 Well-Known Member

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    Re: Seems I have a problem.

    Time to use the YICS rag doll! lol!
     
  12. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    ^^ +1

    Or shopping for silicone hose of the right size that doesn't come from a pothead shop lol
     
  13. hogfiddles

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

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    Re: Seems I have a problem.

    I don't use a YICS tool......yes, I have one--it's in the plastic sleeve that it came in. It's the fancy one, too. I like it--it looks neat and I can show people one at carb clinics.

    dave fox
     
  14. mwhite74

    mwhite74 Member

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    Re: Seems I have a problem.

    YICS tool use is stressful, i always wind up destroying the little rubbers on the tool. I just stuff oiled up rags in and can leave it there the whole time, not worrying if it burns or gets a little warm :).

    Good luck with the sync!
     
  15. Polock

    Polock Well-Known Member

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    Re: Seems I have a problem.

    don't use the tool and live happily ever after
     
  16. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    Aaaand...

    @#$%^&*()_)(*&^%$#$%^&*()_)_+_+_&$$#@@$%^&*&*&^#@#!#@#!!!!!!!!

    Redid the sync with the tool sealing correctly. It idled at 1000.

    Let it cool down, pulled the tool. Put the plugs back in. Put the tank on.

    With enrichment completely shut off it promptly started and idled at a nice 6000 RPM. Fdisk me sideways.

    I guess what upsets me is that I had such high expectations...


    BTw, to answer some of the questions, vacuum caps are new, throttle seals are new, MNMaxims helped me with float levels. Intake boots are not cracked or weathered in any way and are bolted up tightly.

    I wonder if YICS tool making a difference means that there is something wrong with the head.
     
  17. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    Are your copper sealing washers on the YICS plugs in good shape? (are they missing even?)

    Sounds like you have a HUGE leak somewhere... or your throttle cable is hanging up somehow & pulling your leg...
     
  18. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    Washers are OK.

    The leak has to be truly something. Pulling off a vacuum cap doesn't make any difference...
     
  19. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    you're sure the throttle is closing properly too? Many people have been fooled by either a frayed cable or bad routing under the tank before now, myself included.

    EDIT-: and I trust your carb pistons clunk test nicely too?
     
  20. quebecois59

    quebecois59 Well-Known Member

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    Re: Seems I have a problem.

    Is that possible one or two YICS passages are plugged up?
     
  21. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    Been there, done that, fixed it.

    Yes, they did. The carbs were torn apart to the last screw and seal and cleaned ten different ways. I actually took the bodies to a shop to get them into an ultrasonic washer.
     
  22. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    Hm. Dunno. Perhaps one of the big guns will chime in.
     
  23. Kwiski

    Kwiski Member

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    Re: Seems I have a problem.

    Check all your Boots. Then you can also do the paperclip sync. Remove carbs, open up idle speed till you can fit the clip in between wall & butterfly on I believe#3 carb. set all the rest of the carbs using clip under each one starting with #4,then #2, then#1. This should get you in the ballpark. After I did this I also used my vacuum sync tool I used on my multi carbed cars. It worked for me & this bike is gotten me lots of miles with no issues. also make sure that the floats are also not rubbing the sidewalls of the float bowl
     
  24. RickCoMatic

    RickCoMatic Well-Known Member

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    Re: Seems I have a problem.

    6,000 rpm's!

    For the Plant to make 6,000 rpm's ... the THROTTLES have to be OPEN.
    Have to be.

    Not a small Air Leak.

    BIG Air getting in!!!
    Main Jet supplied Fuel.

    I would suspect Cable-related or Linkage-related issues.

    Handlebar Control loose.
    Cable not anchored and pulling.
    Choke and Throttle Cables errantly swapped.
    Throttles stuck open.
    Linkage problem.
    "Something" keeping the Throttles wide-open.

    P.S. You DID put the Plug for the YICS Passage back-in, ... right???
     
  25. MercuryMan

    MercuryMan Active Member

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    Re: Seems I have a problem.

    And the amount of resting rpms is twice what you started with that should be a clue to you. It was running up to 3k now 6k-that is about 70% throttle averaged across your carbs. So back up and realize what must for sure be happening. The cause is yet TBD but the result is your butterfly's are opening and your CV pistons are lifting, or most of them are at the very least.

    Maybe chasing a dead end but when you say 'cleaned 10 different ways' what do you mean?
     
  26. RickCoMatic

    RickCoMatic Well-Known Member

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    Re: Seems I have a problem.

    When Carbs are taken off, cleaned and put-back on, ... it is not uncommon to wedge the Linkage Cable Attachment under the back-side of he Head.
     
  27. SLKid

    SLKid Active Member

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    Re: Seems I have a problem.

    Sounds like you havent really tried much of anything
    Throttle shaft seals
    Especially since you broke the rack.
    Bench sync.
    Set air fuel mixture screws to 2 1/2
    Install
    Spray carb cleaner on intake boots, listen for higher revving.
    Spray on Throttle shaft seals, listen for revving
    Spray on Intake boots, listen for revving.
    Youve got an air leak
    -Chris
     
  28. SLKid

    SLKid Active Member

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    Re: Seems I have a problem.

    Good point Rick.
    I've done that once before.
    Only once though. Caught the mistake when I went to install the throttle cable though. "Oh. You shouldnt be here"
     
  29. RickCoMatic

    RickCoMatic Well-Known Member

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    Re: Seems I have a problem.

    6-Thousand Revs!

    Ain't no Throttle Shaft Seals or some-other minor Air Leak!

    The Throttles are OPEN
    MAIN Jet Fuel entering Combustion Chambers.

    You're closer to the Red Line than you are Idle.
     
  30. adrian1

    adrian1 Active Member

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    Re: Seems I have a problem.

    As above. You have a cable hang up or similar. This is not a cleaning/leak exercise.
     
  31. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Re: Seems I have a problem.

    You sure you didn't simply mix up the throttle and choke cables, or the throttle cable has maybe jumped loose from its perch at either end? The motor cannot run at 6K without the butterflies being open, and that is a mechanical function.
     
  32. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    Big guns or small peashooters, the answer seems to be the same either way. Maybe I'm not so daft :p

    And no YICS blockage would INCREASE revs any way shape or form :?
     
  33. Bushy

    Bushy Active Member

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    Re: Seems I have a problem.

    FWIW .. have had the same problem with torn up yics tool seals..went back to stuffed with oily rags and the last time i synched the carbs ended up with a high idle when at running temp' , about 500rpm high so i did it again and it was right. Either you got th sync' wrong or it's a mechanical fault, for that many revs I'll go with mechanical fault as well.

    When putting th carbs together after cleaning / seals etc did you make sure they were all lined up on a flat surface as you tightened the rail? that they mount together on and that the springs on the adjustment screws were all sitting properly. When i did mine i got a spring sitting wrong somehow but noticed before putting them back on, luckily.
     
  34. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    Throttle moves properly. Although, this did happen after I put the tank back on. Sigh... I'll pull it off again and see if it pinches anything.

    Well, I'm sure I tightened SOMETHING on both sides of the engine... :D Yeah, I'm confident I did.

    Taken apart to the last screw, dipped in chemical cleaner, brush bristles inserted into passages, ultrasonic cleaned at a shop. Jets cleaned separately in Chemtool. Verified light through them.

    Look further up this thread.

    Brand spanking new.

    Done.

    Done.

    I'm sure they are not mixed up. The choke cable moves the valves, not the throttle.

    As for the throttle cable, it seems to be moving properly, but since this happened after I put the tank back on, it's worth a look.

    The second time around with new rubber seals I oiled the tool before inserting (that sounds seriously dirty :D ), made things much easier.
     
  35. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Re: Seems I have a problem.

     
  36. Special_edy

    Special_edy Member

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    Re: Seems I have a problem.

    I have the exact same issue with my bike.
    Bike runs buttery smooth until it reaches operating temperature. Then it will either spontaneously rev to 5k or if you blip the throttle it will stay at 5k.

    I pulled the carbs off and rechecked EVERYTHING twice and it still has the problem. Ive recently pulled them off again and done every check for the umpteenth time, though I havent gotten around to reinstalling them and trying again.
    Carbs ultrasonically cleaned. Pistons passed the clunk test on 3 seperate rebuild sessions, I even polished theis last time. All manifolds meticulously checked for vacuum leaks. Throttle shaft seals replaced, floats set, carbs synced with a manometer, shims done but I may change them around again.


    The throttle does not need to be open to rev to 5k rpm at idle, and none of the vacuum piston are opened up when the problem is occuring(i ran it without the airbox last time to check this). We are talking about a totally unloaded engine not a motor in 5th gear crusing down the freeway. 5krpm only takes a few % throttle when in neutral.
    Having the YICS tool in doesnt effect the problem.
     
  37. Polock

    Polock Well-Known Member

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    Re: Seems I have a problem.

    for whatever reason your only running on 2 or 3 cylinders,your idle speed is adjusted to 1K with missing cylinders. then when it gets warm the rest kick in and away go the RPM's.
    your bad cylinders are probably lean when it's cold and close enough as it warms up.
    when it's cold, start it up, and see which pipe stays cooler the longest.
    look into the enrichment circuit maybe
    maybe turn that mixture screw out,see if that brings up RPM's, evenness across the carbs doesn't matter
    get some new plugs.
    sync doesn't really care if the cylinders are firing or not
     
  38. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    Pulled off the tank, verified throttle cable is OK, verified spark on all cylinders.


    And then it wouldn't start. Just cranked till the battery started dying.

    I'm starting to think this bike is haunted.
     
  39. adrian1

    adrian1 Active Member

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    Re: Seems I have a problem.

    Alright so run us through the symptoms again. Hard to start, then idles at 6k? Anything else? How are those plugs? If you get it started see if one or more pipes runs cool.
     
  40. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    Good point, I'd have to say this is a distinct possibility if nothing mechanical is opening the throttle on you. It can be hard to detect even a 2 cylinder misfire on these engines (ask me how I know!)
     
  41. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    To restate the latest sequence:

    Synched with YICS blocked, idled at 1000
    Pulled YICS tool, put plugs back in, put the tank back on
    Started and immediately revved to 6000
    Pulled the tank, put the gas bottle on
    Checked throttle linkage
    Checked spark on all cylinders.
    No start
     
  42. Polock

    Polock Well-Known Member

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    Re: Seems I have a problem.

    if you used a paper clip to do a bench sync and never turned the idle knob down to lower the idle, there's a chance that 6K is what the idle is set for.
    it might be set high enough to defeat the enrichment circuit.
    try backing off the idle screw till it's off the linkage then go in till it touches and then in 3/4 to 1 turn.(that's a guess), no yics tool.
    if you pull a vacuum cap and nothing happens, could be because that cylinder isn't firing.
    sometimes a plug will fire outside the engine but not when it's under compression
     
  43. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    So, I turned out the idle knob.

    Got it to start and idle at 1000.

    And then it jumped to 3000. At least it's not 6K...
     
  44. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    Still misfiring on a couple of pots at cold startup, idle is adjusted to 1000 on the firing cylinders & then as the engine warms, the other 1 or 2 start firing and the revs shoot up would be my educated guess...
     
  45. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    Sounds logical.

    What would be the next step from here? New coils?
     
  46. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    Re: Seems I have a problem.

    New plugs not coils!!! (unless you know something we don't, have you checked the resistances?)

    I've found bad plugs can cause hard starting & on multi cylinder bikes can cause a miss until they warm slightly, plus they're a cheap option. What code number is on the plugs that are fitted?
     
  47. adrian1

    adrian1 Active Member

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    Re: Seems I have a problem.

    We're still waiting for you to tell us if one or more pipes are cooler. At least that will narrow it down to a particular cylinder(s)
     
  48. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    All the pipes run hot, as far as I can tell. #4 seems to be hotter than the rest, but that's about it.
     
  49. Polock

    Polock Well-Known Member

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    Re: Seems I have a problem.

    you can't wait till their hot, check the pipes as soon as you start it, while it's still at 1K.
    don't even sit on it to start it, kneel down by the pipes and feel for heat as soon as it starts.
    go get some new plugs.
    then let the bike warm up real good,(3K idle, choke off) set the idle to about 1500, and start the sync again and try to keep that 1500 while you sync.
    then go to 1200 and start on the mixture screws
     
  50. JPaganel

    JPaganel Well-Known Member

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    Re: Seems I have a problem.

    So, the plugs I have in it are B7ES. The parts catalog says they should be BP7ES.

    Do I not have the right plug?
     

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