Tell me about these plugs..
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Thread: Tell me about these plugs..

  1. #1
    Senior Member Dabba's Avatar
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    Tell me about these plugs..

    So I've posted about losing power which I suspect is an issue with weak spark (But no, I havent had time to test it yet), but lately its been getting worse. While the issue used to be intermittent, now it's always low on power, and I can smell unburned fuel in the exhaust on startup, which is new. Today I noticed some blue smoke right of the right pipe which I thought was odd, so I figured I'd pull the plugs which honestly have been due, and I figured I may as well look at them before testing the ignition system.

    The right side was very oily around the spark plug hole removing it, and on the plug itself with significant buildup, the left side looks relatively normal to me, just used. What can be going on with that right side on a newly rebuilt engine? I'm a little worried and annoyed. Should I just replace the plugs and keep going or should I be looking elsewhere?

    Also do these findings also point to a weak spark issue? Or something else entirely?

    Right side
    Tell me about these plugs..-plug1.jpg

    Left side
    Tell me about these plugs..-plug2.jpg
    1978 CB400T II

  2. #2
    Supporting Member Yendor's Avatar
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    You don't say how many miles these plugs have on them.

    If under 2000 I'd say you may have a problem.

    Over 3000+ I say just plain old age.

    The right clearly is picking up more deposits then your left, I don't think oil around the edge of the plug came from anything internal to the cylinder.
    Were they torqued down correctly?
    1970 CB 350 CAFE - Current Project on the bench,
    1972 CB 350 K4 Red - Now a Happy Rider ! !
    1972 CB 350 K4 Green (My Sons) DONE - YES !,
    1st Bike 1970 SL 350 (Brought home in Parts - Trailer/Trunk/Back Seat - I miss that bike),
    2nd - Bike Kawasaki 750
    3rd - '73 XLCH 1000

  3. #3
    Senior Member Dabba's Avatar
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    I honestly don't remember of I replaced the plugs when I rebuilt it, and it has less than 3k on the rebuild. I'm also not sure if I had em torqued down correctly. Do you know the proper torque off hand?

    I'll replace them and see what happens.
    1978 CB400T II

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  5. #4
    Senior Member doode's Avatar
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    Why not try new plugs and caps? And trim the plug wire while you're at it.

  6. #5
    Senior Member Dabba's Avatar
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    Quote Originally Posted by doode View Post
    Why not try new plugs and caps? And trim the plug wire while you're at it.
    I don't have time for anything crazy. I'm replacing the plugs because they're shot and gonna see how it runs, then hopefully test resistances to see if my CDI is shot or not. When? Who knows. I'm in PA school, so as long as it runs and I can enjoy it back and forth to school, everything else takes a back seat! ha

    Thanks guys
    1978 CB400T II

  7. #6
    Senior Member ancientdad's Avatar
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    Quote Originally Posted by Dabba View Post
    I don't have time for anything crazy. I'm replacing the plugs because they're shot and gonna see how it runs, then hopefully test resistances to see if my CDI is shot or not. When? Who knows. I'm in PA school, so as long as it runs and I can enjoy it back and forth to school, everything else takes a back seat! ha

    Thanks guys
    If by crazy, you mean something that would take only 10 minutes longer to change the plug caps and trim the wire ends before installing the new ones, then... I get it, but ordering the parts would take longer than the installation and only a few more minutes than just plugs themselves.

  8. #7
    Super Moderator longdistancerider's Avatar
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    The NGK part number for the plug end caps is XD05F
    ancientdad likes this.
    Jim O'Brien
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  9. #8
    Senior Member Dabba's Avatar
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    Quote Originally Posted by longdistancerider View Post
    The NGK part number for the plug end caps is XD05F
    Edit: Will test these too, I see you have specs in the sticky
    Last edited by Dabba; 05-19-2017 at 03:38 PM.
    1978 CB400T II

  10. #9
    Supporting Member Yendor's Avatar
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    Here is the Torque recommendations right from the NGK Site.
    Right CLICK and OPEN in a NEW TAB to view full size.
    Tell me about these plugs..-plug-torque.jpg
    1970 CB 350 CAFE - Current Project on the bench,
    1972 CB 350 K4 Red - Now a Happy Rider ! !
    1972 CB 350 K4 Green (My Sons) DONE - YES !,
    1st Bike 1970 SL 350 (Brought home in Parts - Trailer/Trunk/Back Seat - I miss that bike),
    2nd - Bike Kawasaki 750
    3rd - '73 XLCH 1000

  11. #10
    Senior Member Dabba's Avatar
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    Quote Originally Posted by Yendor View Post
    Here is the Torque recommendations right from the NGK Site.
    Right CLICK and OPEN in a NEW TAB to view full size.
    Click image for larger version. 

Name:	Plug Torque.jpg 
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    Thanks, I was looking for where I saved the manual but.. that works!
    1978 CB400T II

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