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Thread: Spark plug cap failure FE390 FE450 FX450 FE570

  1. #1

    Default Spark plug cap failure FE390 FE450 FX450 FE570

    As our bikes age this seems to be a possible issue that causes a lot of tail chasing . It has multiple symptoms that could have you thinking fuel injector, fuel pump , fuel filters . The husaberg OEM can be replaced by NGK VBO5E NGK part number 8408

    Symptoms:

    flame out as bike is warmed up just off idle with back fire

    hard starting when hot

    will only run at higher RPM



    Unscrew the cap from the wire check with meter should be close to 5k ohms if you have no reading get a new one . This has happened to 3 different bikes one bike twice

    As I was typing I figured let me try to fix one I took needle nose pliers and tugged the screw lug out it was black with carbon cleaned it up with scotch brite, put some die electric grease on and pushed the star washers down with a blunt pick now it reads 5.2kohms



    The image below shows the correct reading after the arching oxidation was polished off the threaded nut that the spark plug wire is attached to

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    2017 300XC
    2011 250XC sold

    2010 Husaberg FX450
    2009 Husaberg 570 slant 70 Blast Sold
    2008 530EXC R sold
    2007 300 XC-W sold
    2002 200EXC Had to try the 200 what fun! sold

    2009 Honda 450X sold
    2003 XR650R street legal sold
    2001 CR250R street legal sold
    2000 XR650L sold
    1980 RM80 sold

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  3. #2

    Default Re: Spark plug cap failure FE390 FE450 FX450 FE570

    Took the fx450 out for a few shorter test rides and one long ride itís been running flawlessly no flame outs . My theory on whatís happening as the spark plug ages it builds up carbon on the tip that combined with the carbon build up on the lug creates enough resistance to drop the spark at low rpm when trying to crack the throttle open and generate a burst of electrical energy needed to increase the rpm . Changing the spark plug may be enough to help the circuit operate properly, when the lug has minimal carbon build up . But at some point this will not help . I believe this is a hidden issue that plagues a lot of bikes flame outs suck and give you no confidence in the bike and creates a dangerous running condition.
    2017 300XC
    2011 250XC sold

    2010 Husaberg FX450
    2009 Husaberg 570 slant 70 Blast Sold
    2008 530EXC R sold
    2007 300 XC-W sold
    2002 200EXC Had to try the 200 what fun! sold

    2009 Honda 450X sold
    2003 XR650R street legal sold
    2001 CR250R street legal sold
    2000 XR650L sold
    1980 RM80 sold

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