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Thread: Possible Engine Knock?

  1. #1
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    Question Possible Engine Knock?

    Hello, hope everyone is doing well!

    I have recently purchased a 2004 XB12R. I love it! Although I am a little worried as the engine is making a noise that does not sound like just the valve train. I hear it mainly near the front cylinder and as the bike warms up the noise gets quitter. The bike only has around 5,000 miles on it. I have checked the tension on the primary chain. I changed the oil to Royal Purple 20W-50. I also changed the exhaust to the Buelltooth XB-GT. Maybe this is a normal noise?. I took a short video of what the bike sounds like. (Sorry about the bad quality.) https://youtu.be/RQB0NjJS3w8

  2. #2
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    If you really think you have a knock, take the primary off, take out the spark plugs and spin the motor over by hand and see if you can feel the knock. "Push" the piston one way with the crank to "load" it, and then see if you can somewhat lightly go backwards and listen/feel for it.

    Here is a similar test

    https://www.youtube.com/watch?v=pYleKxjl0uY
    Last edited by 34nineteen; 12-12-2019 at 08:12 PM.

  3. #3
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    Thank you for the reply. I will try to do the test tonight. If not tonight, I will this weekend. I really appreciate it!

  4. #4
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    I was able to do the test last night. I did not seem to have any play when I pushed on the pistons. As I spun the engine by hand I could not feel anything out of the ordinary. I did this a few times just to be sure. Maybe the noise is just piston slap?

  5. #5
    Senior Member lunaticfringe's Avatar
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    sir: the test in the vid is excellent but is only suitable for automotive-style one-piece crankshafts called "babbitt bearing cranks". will reveal nothing for a roller-bearing press-pin style crank and rod assembly which is standard fare in XB...XR...H-D big twin motors. you do NOT have piston-slap.
    secondly....nothing can be accurately diagnosed from an amaeturish vid though you do seem to have an inordinately noisy motor.
    therefore, do this:
    1-beg...borrow...or purchase an inexpensive automotive style stethoscope. a local auto shop might lend you one. the screwdriver-hearing-aid method only accurate for pros and is more a "feel method" than anything else.
    2- excluding the left side of your lump...there are only 3 distinct XB motor areas that will elicit a noise similar to yours and this is ASSSUMING you have NO oiling or filter issues. they are: the area above the head known as the "rocker box" assembly....the cam cover assembly....the crank/rod/pin assembly.
    3- using a stethoscope method get some heat in the motor...set the idle to 1100rpm....then from the right side of the motor start to listen to those 3 distinct areas. areas #1 and #2 if having developed an issue will elicit a tap or tick. area #3 will elicit a knocking type noise that becomes more pronounced as the throttle is lightly revved.
    this is where i would commence a proper and accurate diagnosis.
    if you cannot locate a stethoscope....can't get some help...or lack the skills to attempt this procedure then have a local person or shop familiar with sportster/XR motors do it for you. if it were mine i absolutely would NOT ride it till proper diagnosis done.

    NOTE: this is an XB with a faulty crank/rod/pin assembly and excessive piston-to-cylinder dimensions.

  6. #6
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    Thank you for the information! I will poke around with the stethoscope. I actually brought the bike into the dealer and one of the techs listened to the bike just for a few seconds and said it sounded fine. But the engine was warmed up so it was difficult to hear at the time. It really does not sound normal. I will take your advice and not ride it until I figure out where that noise is coming from.
    I appreciate your replies and will keep you updated!

  7. #7

  8. #8
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    Hello!

    I purchased a stethoscope and listened to a few places. Thankfully the noise is not from the bottom end! It seems to be coming from the top of the front cylinder head on the right side of it. That is where it is the loudest with the stethoscope.

  9. #9
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    Hydraulic lifter clogged, stuck ?

  10. #10
    Senior Member Silverrider's Avatar
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    Quote Originally Posted by njloco View Post
    Hydraulic lifter clogged, stuck ?
    If that is the case lifter lube will help that .



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