WILL DO ALL Z50 XR50/70 CRF50/70 CT70 ATC70 TRX70 TRX90 MOST 4 CYCLE 50'S AND 70'S 12MM PLUGS = CT90 ATC90 CT110 ATC110 OR MOST OLDER 90CC HONDA'S Threads There are currently three spark plug thread diameter and pitch sizes used on motorcycles and ATVs: 10 mm x 1.0, 12 mm x 1.25 and 14 mm x 1.25. There are currently two thread reaches (lengths) used: 1/2 inch and 3/4 inch 327A