Motorcycle Repair: honda cb125j helicoil, honda cb, thread pitch

Question
hi.ineed to fit a helicoil to my sons 1979 honda cb 125j,i have never done this before so i dont know what size to get.can you help me please?

Answer
That should be a 12 mm x 1.25 thread pitch. If you take the plug to the auto parts store you can be sure you are getting the right helicoil.  Be careful if you are planning to install the helicoil while the head is still on the engine.  It can be done but you need to be sure the valves are closed and that you apply lots of grease to the tap to be sure you capture any chips so they don't get down into the cylinder.

Regards
Rich