After the spark plug thread in the cylinder head stripped I staggered about holding my head and moaned NOOOOOOOOOO!!!! for a while then started to think about how to fix it.
|the threads have completely gone
I could sort things by installing an insert. This means cutting a new, bigger, thread and then installing an insert with a 10mm x 1.0mm internal thread. There was no way of doing this with the engine in place, the frame is in the way, so out came the engine. It seems possible to do the work without removing the cylinder head.
|Removing the engine is pretty easy on a small bike like this. I made this timber frame to hold the engine. I clamped it in my "wallmate" to hold it steady.
|I bought a thread repair kit consisting of a tap and inserts of various lengths by German company BGS Technic.
|I connected the tap to a 3/8" drive socket, extension & tommy bar.
|An NGK CR8E spark plug and a tube of Loctite 272 high strength, high temperature thread lock fluid.
|Here I go cutting thread. If I get this wrong I've wrecked the engine - so no pressure then.
|The tap quickly starts to cut the thread. I work it backwards and forwards in increments and regularly remove the swarf and apply new grease.
|The completed new thread - it looks good.
|I apply thread lock on the outside of the insert. Hopefully this will hold it in place permanently.
|The finished job with the insert in place