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problems with cylinders

Discussion in 'XJ Technical Chat' started by senzei, May 21, 2011.

  1. senzei

    senzei Member

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    :twisted: Hi Lads have a real problem that seems to not want to go away and now have given up using a garage as I seem to just give them money time after time, so if I am unable to sort this problem I think I will have no choice but to call it a day. It will be such a pity as I have paid out so much and done so much. Hope one of you will be able to help as I have had enough now.

    :roll: :roll: The machine has had a new turbo/seals etc carbs have been taken apart and rebuilt after sonic cleaning them. The carbs have been now cleaned etc 3 times as everytime the bike comes back it is used once.
    Then when used again either 1 or 2 of the cylinders won't fire, pipes are stoned cold, this keeps on going on and everytime they take her back and tell me they have striped her (carbs) flushed etc costing £200 or close each time.
    Would not mind but the same thing happens everytime at this time I have 2 of the cylinders not working but this time I am not letting anyone else touch her as I am so *issed of have spent ££££££££££££ still to have this problem.
    When I last picked her up from the garage I rode a fwe yards only for her to stop :roll: this time 1 cylinder did not work, the guy removed the plug and cleaned it put it back then all was fine, until fired the next time same problem this time it is the other side, so it is not as it is the same side/cylinders each time. Can anyone please advise what I can do 8O I want to enjoy the bike had it a year only to be worked on. Any ideas
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  2. SQLGuy

    SQLGuy Well-Known Member

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    Nice bike!

    What did the plug(s) look like after the cylinder stopped firing? If they were clean and wet, we're looking at an ignition problem. If they were clean and dry it's some sort of fuel starvation. If they're fouled, there are a few possibilities.
     
  3. pirok

    pirok Member

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    What # of cylinder are we talking about? Spark plugs should be NGK BP8ES or equivalent. IF it's true the carbs have been dismantled 3 times without any change it's not the carbs, but i won't bet on it.
    I've had a simular problem turned out to be the pilot air/pilot screw circuit that were clogged up. (carbs) Especially those tiny little holes in the float bowl - where the brass tube go in - are difficult to clean up.
    If it's #1 and #4 that's having the problem it's probably the coil. Once i had a cracked coil which gave the strangest symptoms.
    More detailed information wanted.
     
  4. tskaz

    tskaz Active Member

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    I agree. We need to know what the plugs look like. We also need to know what you have replaced/tested so far.

    Have you:
    Tested the coils/wires/boots?
    Done any tuning?
    Checked valve clearances?
    Replaced/charged battery?
    New plugs?

    The more info you provide the more we can narrow it down.
     
  5. senzei

    senzei Member

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    Hi all firstly many thanks for the very fast way in which you respond, when I posted about this 1st both cylinders on the left side as you sit on her did not work. Went out today (22-5-11) she started but what I found strange was that this time both of the end cylinders where stone cold, would have thought that it would have been the same as before. Anyway took out the plugs see attached, cleaned both of put them back and all now fire, have noticed that 1 or 2 seem to run hotter then the others at the start is that normal?
    Does anyone know about the fuel cap my caphas no hole in it and have been told that there should be a hole, and to drill one into the cap.
    Thanks all, no doubt will need to take plugs out and clean again soon.

    New Battery the guys are supposed to have pressure tested, tunned etc. hence why I am a very poor motor :cry: :cry: :cry: cyclist
     
  6. murray

    murray Member

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    Hi ,I noticed from your picture of the plug that you are using
    a BPR8ES, not a BP8ES,could this be contributing to the problem ?

    cheers,murray9982
     
  7. senzei

    senzei Member

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    Well if you others think it is the plug (incorrect ones) then I will buy 4 BP8ES, THE PLUGS ARE what the guy put in, they are new.

    I will await what others also think, many thanx for the info
     
  8. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Unless the plug CAPS have been replaced, the bike has resistor caps. You don't want to run resistor (R) plugs with resistor caps. I would certainly start there; and while you're at it, ensure the caps are tight on the wires (they screw in/on.) If you have a loose cap, unscrew it off the wire, lop off about 10mm or so, and screw the cap back on. (There's a threaded "spike" inside the cap that screws into the end of the wire.)
     
  9. RickCoMatic

    RickCoMatic Well-Known Member

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    If it were my Bike; I'd modify the Ignition Wiring to be High Performance.

    I'd replace the Original Fuse Panel.
    Replace ALL Relays.
    Get rid of the Stock Coils and Wires.
    Race Prep the New Wiring; complete.
    (Solder & Heat Shrink => Everything.
    Eliminate Plug-in's and Terminal-ended Wiring Connection Points.)
    New High Performance Coils and Wires.
    (If the Coils have Terminals where the Wires Snap-on to Posts, ... Align the Wire to the correct angle coming-off the Coil and solder the Plug Wire Terminal onto the Coil Post.)

    Racing Plugs: Comparable to Brisk LR12YC

    In short, ... REMOVE any possible weal link in the Ignition Circuit and REPLACE aged components with New "Performance Rated" goodies.
     
  10. Ground-Hugger

    Ground-Hugger Member

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    I agree with Bigfitz52 I had exactly the same issue you are having with my 83 XJ750. The PO had installed BPR8ES plugs in the engine once I switched to the BP8ES there was no more issue with not firing correctly. The problem with the BPR8ES is they are resistor plugs and as such cut down on current to the electrodes by 5 ohms.
    The stock plug caps have resistors in them and they also reduce the current by another 5 ohms. So you end up with 10 ohms resistance where you should only have 5 ohms resistance. In a nutshell you are luck if you have enough current to the electrode to produce a spark. So its hit or miss as to how many of the plugs fire.
     

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