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  1. #1

    Problem with new engine

    So I have the new engine in and it seems to start and run fine (1998 XL1200), although it does run rough at idle. I have put about 2.5 hours on it at this point and have been playing with the carb settings. My problem is this:
    The thing will not go above about 38mph. I originally thought that this might be due to carb settings but then I pulled the plugs out. The #2 cylinder doesn't seem to be firing. I am ASSUMING that it is getting fed with fuel/oil (I premix now) because it has been running for the 2.5 hours and the piston is still intact. When I pulled the plugs, the piston on the #2 cylinder looks like nothing has been ignited in it either...it's clean as it was when installed. The other two pistons have the black deposits on them as is common. Has anyone seen this before and/or does anyone have suggestions? I am going to test for spark tonight and see what's up.
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  2. #2
    Flying Scotsman's Avatar
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    Test for spark.
    If theres none at #2 then try triming back the plug wire.
    What head are you running with those plugs.

  3. #3
    I tested for spark with a spare spark plug and it fired fine but I noticed that the plug was very loose. I tightened down the plug clip inside the wire boot and it seems to latch on much better. I am thinking that the vibration of the engine at idle may have jolted it loose. I'll be on the water tomorrow so we'll see if my theory about the plug wire is correct.

    The head is a billet aluminum Triton engineering head...there is a decent pic of it below (minus the red arrow).
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  4. #4
    Mpeavler's Avatar
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    Quote Originally Posted by Flying Scotsman View Post
    Test for spark.
    If theres none at #2 then try triming back the plug wire.
    What head are you running with those plugs.
    x2

  5. #5
    That didn't fix it. I am getting spark on that cylinder but it doesn't seem to be firing.

  6. #6
    Mpeavler's Avatar
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    Gas, Air, Spark and you should have fire. Have you done a compression check on this engine? What type of PSI are you at?

    M

  7. #7
    Flying Scotsman's Avatar
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    What Mike said if theres gas and spark it should fire unless the pison is compromised.(no comp)

  8. #8
    54lariatxp's Avatar
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    Have you switched plugs around just for giggles, I have a 2 cylinder welder that needed a tune up, bought new parts along with plugs and one was not firing, brand new and defective, bought a new one and all was fine.

  9. #9
    I have swapped plugs all around and the same thing happens. I will do a compression test in the morning, but when I finished building the engine, I did a compression test and was at 150psi on all three cylinders.

    I gave it some more thought tonight and wondered if maybe the seal between the engine casings has blown out somewhere around the number 2 cylinder. If that was the case, when the piston is on the down stroke (which would be pushing it through the ports to the combustion chamber), the air/fuel mix would be seeping out of the leakage area rather than being transferred to the chamber. This would also keep the cylinder walls lubricated properly, preventing seizure on that piston. Some of the air/fuel may make it to the combustion chamber, but not very much. I am going to run some UV dye through it tomorrow morning and use a blacklight to see if I can find any leaks.

    So here's where I stand now:
    1) check compression on all cylinders
    2) compare spark strength from known good cylinders to bad cylinder.
    3) check for leakage coming from engine casing, resulting in need to reseal casing.

    Let me know if anyone else has other suggestions. Thanks for everyone's help so far!

  10. #10
    Moderator OsideBill's Avatar
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    I would suggest keeping it simple here, the case seal leak would cause lean condition which is not your issue, as it is not firing at all.

    Fuel? spark? compression? answer these three questions and you will find your issue. The manual will walk through checking for spark and testing the coil and plug wires. Pull the flame arrestor off and run it so you can look down in the throat of the carbs to see if fuel is being delivered, and a compression test is self explanatory, though there is a right and wrong way to do it.

    Do you have a service manual? http://greenhulk.net/forums/showthread.php?t=9546
    Compression testing http://greenhulk.net/forums/showthread.php?t=71862

    Let us know the answers to these questions and we can give more detailed help from there.

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