I needed to replace what I was told a broken cam chain.(I bought the CX500 on this info). After removing engine I immediately saw that cam chain gear was broken off. It readily appeared that I would need a special tool to remove the flywheel. After removing bolt in center of flywheel assembly I saw some threads. From some of the mounting bolts I discovered that the threads were 20mm. While at a local auto parts store getting parts for a ccar project, I noticed an oildrain plug with 20mm threads tha looked as if they would match the threads on my CX500. I purchased the plug and as soon as I got home i tried screwing the plug into the fkywheel assembly and behold the flywheel assembly came off. The plug cost me less than $5.00. From another CX500 I have I got the parts I needed to fix the broken cam chain gear. I don´t even know what the oil drain plug fits, but I don´ care. It removes the flywheel assembly of a CX500.