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So I pulled the plugs today and noticed that the front plug came out easily until the last few turns, then it got a bit difficult. I figured maybe some carbon had built up on the end of the plug and was causing the issue. Once I got the plug out, I notice a sliver of heli-coil sticking out of the plug hole. And surprise surprise, the rear head has a heli-coil too.
Looking at the threads in the head, I'm thinking I have the wrong spark plug as it has longer threads than those in the head. And that could be a problem when removing due to build-up on the exposed threads.
My machine is a '75. Do I have earlier shallow-thread heads, or do the heli-coils just make it look that way?
Last edited by Rusty Axle; Apr 28, 2019 at 09:33 PM.
Reason: add info
75 had the shallow plug hole still, that coil looks right. Plug on the other hand looks like a long reach, be real close to the piston top I'd suspect and yeah carbon build up will walk a helicoil out on you if it binds up.
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Spark Plug Threads Question
