Small Engines (Lawn Mowers, etc.): cross thread spark plug, spark plug thread repair, thread repair kits

Question
How can I repair spark plug threads on Kiwasuki 18 hp engine? This is aluminum head. This is the sixth year I have changed the plugs.  It appears I have not been tightening the plugs tight enough because the washers have not been making contact with the head.  This allowed carbon build up & contributed to the problem.  Can I re-tap the head and clean the threads with a tap?Bottom tap Or tappered tap?

Answer
HeliCoil, www.helicoil.com, sells a spark plug thread repair kit.  I actually have the kit, but have never used it...they are kind of expensive...especially if it just sits in your tool box.

Many auto parts stores also sell thread repair kits.  Most kits recommend removing the cylinder head so you do not get metal shavings in the cylinder...makes sense but takes a lot of time.  Some of the "old timers" have told be they used to use a lot of grease on the tap to catch the shavings...this way they didn't have to remove the head.

Most kits come with the exact tap you need.  I would recommend trying to repair the head or opt for buying a used one on E-Bay.  

Let me know if you decide to use a thread repair kit.  I would like to know how it goes.

Eric