05 YZ250F head Heli Coil Spark Plug hole?

Anyone know what size Heli Coil I need to buy? 05 YZ250F spark plug hole has to be drilled / tapped and heli coiled. I don't want to buy a big kit so I need the correct size to go back to OEM plug size?


Might be better of going to the dealer, lol.

It's going to be M10 with a 14mm reach

my experience ( two friends bike & one mine) heli coil spark plug has been a problem you reduce the area that the gasket washer makes contact

I have had them come loose after a couple rides ( I do acetone the area and locktite the helicoil)

I have had better luck with a thread insert

when you drill the hole and tap it coat them with Grease that will help hold the chips so less will fall in the engine

heli coil is easier than an insert

A friend of mine stripped his spark plug threads on a 99 rm250. He took his head off, completely filled the spark plug hole with Devcon, waited 2 days, then re drilled and tapped the hole to the original thread size. He still runs that thing around and that was 4 years ago. He puts a little anti seize on the thread with each plug he puts it. Worked great.

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