| Re: Honda BF225 Trouble need help!
I have seen this happen on a few BF225's, albeit it's not super common. If you are expecting it, you can deal with it before you create a problem like what you have done here. I have seen the threads break cleanly off from the plug, and the rest of the spark plug come out (basically like leaving a threaded pipe in the spark plug hole). Now if I ever come across a plug that doesn't want to come out, I tilt up the motor and fill the hole with Aero Kroil. Let it soak. Then wrench the plug back and forth slowly. Sometimes you have to walk away and let it soak some more. Doing this, I have never had a spark plug break or left threads behind.
If the spark plug broke off in the head, then you need to remove the head, take it to a machine shop and let them drill it out and helicoil it. If you just left some of the threads behind, or galled up the threads, you may have some easier options. One is to tap it very slowly with a liberal amount of grease on the tap. The grease will catch the shavings, which will be very very fine. Go slow, and work the tap back and forth in very short strokes, taking time to completely remove the tap fairly often, clean off the grease, and regrease it. You can also tap it from the inside out by using an expandable tap (I got mine from Mac Tools). Insert the tap into the combustion chamber, expand it, and start tap from the piston side out. If the threads are heavily galled, this approach may not work too well.
The service manual says to remove/inspect/clean the spark plugs at 200 hours, and replace at 400 hours. At the 200 hour service, I remove the plugs and coat the trheads with anti-seize. If I am repowering a boat that will be kept in a slip, I remove the plugs and coat the threads before the customer ever gets the engine.
Hope this helps.
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