I was trying to check the compression on a Echo SRM210 string trimmer. I screwed in my compression gauge pulled the cord and the piston hit the end of the gauge. I have had this problem before with some engines. I have 3 compression gauges and all have the thread length too long. Does anyone make an adapter for the short reach spark plugs so I can test the compression. The spark plug is a 14mm thread plug. bpm8y. my ngk book say's it has a 3/4" reach. Thanks for the help.