I went to change my front gearcase fluid and the 8mm hex head was badly stripped. I finally got it out by drilling through it and using a bolt extractor, but now I'm confused about the drain plug size. I bought a M18x1.50 and it ended up being a little bit too small. A M20 was too big, and M19 doesn't appear to exist. It finally dawned on me that 3/4" standard bolts are right in between M18 and M20. I found that a 3/4-16 fine thread seems to fit well, but was hoping someone with more background might be able to confirm. I think I'm mostly confused because I always assumed the engine would be all metric, but this one seems standard. Thoughts? Thanks!