Stock is an m8X?.
No worries. I'll just go to an M10X1.50.
Down to the hardware store to get a 8.5mm drill bit for the correct size hole for the tap, a M10X1.50 16mm bolt, and a fiber washer.....
What's that? The drain hole was already stripped out, and the plug is in there right now IS an M10X1.50?
Back down to the hardware store to get a 10.2mm drill bit, a 12X1.75 16mm bolt, and a fiber washer.....
Let's do this!
In case you were wondering, I made it at Techshop. They have a work bay where you can work on your car, motorcycle, moped... whatever! There are 3 of them around the SF Bay Area, so it's pretty convenient. There's others around the country and they have lots of tools and workshops. Wood, Metal, Fabrics, Electronics and more. It's rad.
Check it out here: www.techshop.ws
Step 1: Time to Drill.....
It's hard to get at the bottom of the engine case with the drill, so I just leaned the whole bike (a 1978 Puch Maxi, BTW) over on it's side, and propped up the rear to get good access.
I actually used a 13/32 drill bit. It's all I could find at the local hardware store. It's supposedly close to a 10.3mm drill bit. Speaking of hardware store, Weird Al Yankovich!
I put a good gobb of grease on the tip of the drill bit. This is supposed to catch the chips from the case while you're drilling. This motor is NOT coming in half, so I want to minimize the risk of putting chips into the motor. This is not the ideal way to do this, but it's a lot better than nothing. I think. Or hope. both.
Try to drill straight. Take it nice and slow. Like a glass of very expensive whiskey. Enjoy it.
When you're done, wipe that crud off from the drill bit. It's gross.
Step 2: Commence Tapping!
Done tapping? Let's take out the tap and put in our new drain bolt!
Let's see if it fits. Turn in the M12X1.75mm bolt, with the fiber washer finger tight. Looks good? Okay, tighten it with a wrench. Not gorilla tight. Snug.
Add your favorite oil or ATF to the motor. Give it a few minutes, then check for an oil leak coming from the new drain plug. If it leaks, cry. I think that's about it. Oh yeah, clean the crud off from the tap. That's gross.