Author Topic: Did something dumb: think I x-threaded a spark plug  (Read 643 times)

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Offline BlackMax

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Did something dumb: think I x-threaded a spark plug
« on: February 16, 2010, 10:58:28 AM »
How embarrassing....  well, I did it a little while back, and hoped it was just my imagination; but, I know it's not.  I had the engine rebuilt, and lots of work done on the head.   When I got everything back, I had trouble tuning the bike, thus the plugs were in and out, a lot.   Long story short, I ended up having the #1 plug (one on the far left) really hard to screw in the last time I did it.  I should have backed it out and applied some lube....but no..I kept going, thinking it would thread normally at any second.  Well, it never did.  I got the plug all the way in, and it's been running just fine for a while; but, I know it's wrong.  In fact, I just looked at the angle of the #1 plug vs the angle of the #4 plug, and they are clearly different.  Thus, I'm sure I x-threaded it, and it'll be okay until such time as I have to remove that plug.  Then, I'm guessing it's not going back in , since the threads are shot.

Sooooo, I've heard that this isn't the end of the world, since it's an easy plug to get to?  I've heard of a back-out tool or something that can be used to re-thread the hole?   Is this right?   Will I get a mulligan on this screw-up?  Can anyone give me the low-down on what I've done and if/how it can be fixed with the head still on the motor?

Thanks in advance!!  I feel like an idiot.
« Last Edit: February 16, 2010, 11:00:06 AM by BlackMax »
1978 CB750SS, 4-1 Yoshi, Pods, 3-angle valve job, ported chambers, ported intake, 41a cam

Offline Sporkfly

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Re: Did something dumb: think I x-threaded a spark plug
« Reply #1 on: February 16, 2010, 11:36:39 AM »
If you have good threads at the bottom still and didn't cross them too badly, you can try a back tap:



If they're really buggered you might need to do a helicoil/timesert/etc.




I just purchased a back tap from northern tools to give it a shot on my #4... I can let you know how it works out. Of course, head removal is the safest method. Thread inserts can be done without removing the head, but it's a risky operation.
1977 CB550K
1979 GL1000 - Current project, winter '09-'10
1979 CX500
1976 Suzuki GT500 Titan