Spark plug threads

[jacobmarley]

Took the spark plugs out to service them, one of them came out with some bits of thread on the spark plug thread, there was also some debris in the spark plug hole which I was able to remove, I vacuumed the cylinder out with a fine pipebut nothing came out. Concerned there are some bits in thier. Have made sure engine not rotated since this happened.
Is it head off or does anyone know another method, also what is the fix for worn threads as this could happen again, are there inserts available, if so where can I get them.
Any advice appreciated.- Jacobmarley

[Steve R]

Helicoil, most engineering firms will do this, not expensive but head should come off, its really not that difficult though.

[jacobmarley]

I,ve put helicoils in myself on other situations but I thought spark plug holes were tapered toward the chamber and that a helicoil was straight, is it a special helicoil for spark plug holes - thanks Jacobmarley

[m1ks]

You can buy helicoil kits specially for spark plug inserts, the difference is rather than a selection of inserts you get the one type and a drill bit to ream the plug hole, first process is to drill out the plug hole with the supplied bit in the kit to accept the helicoil insert.
Save yourself the annoyance and take the head off to do it or have a a company do it for you.
I tried the 'easy method on the Z750 I used to have, i set the piston to TDC, tapped it, vacuumed it, helicoiled it the vacuumed it again and again with a rubber flexible pipe extension and thought the thing was clear.
A couple of months later it was a new head gasket and proper clean.

[Pigford]

Plug holes are parallel... NOT tapered - thats for pipe fittings

[zed1015]

Carbs off . Turn engine so inlet is open but piston is as close to the top of the bore as it will go before inlet closes. Have compressor running with pipe taped into the required inlet so when you slowly tap the helicoil thread the swarf gets blown back out of the plug hole (wear goggles). After fitting helicoil and breaking off tang with long nose pliers give it another blow out down the plug hole with the exhaust valve open and even try the hoover trick until you are happy its clear.