I did not know about the JIS heads, interesting knowledge. But as someone mentioned, they're often stripped long before they get to me. And I also think Allens are superior to Phillips in general, less likely to cam out even with the right fastener (YMMV).

I did make a point not to get stainless fasteners when I upgraded. As previously pointed out, stainless has a bad propensity for galling and corroding other metals. When I worked in food processing machinery it was all stainless and everything had antiseize on it to reduce galling itself. They work and look pretty, just remember to grease them. 

You learn something new every day.  I have been pounding the $#!@& out of side and center case Yamaha screws using Phillips #3 drivers for years.  I always thought that JIS were marked with a dot or cross.  They are not always marked!

Same here JayB, just received today a set of the JIS bits that fit into a nifty T handle holder and it’s like “ why did I wait to do this ? “      $20 from Yamabits

If i was competing i would use allen head screws as cases and the like are on and off like a brides nighty . For looks i prefer JIS screws .
As far as stainless goes , it's just the worst metal to work with and think on our era of bikes should be avoided.
The food industry loves stainless and sounds like you to have had the privilege of removing fittings that go in easy but then will not come back out because they've galled up .
So now you know about JIS. Good on here you know.

I haven't started my rebuild RT2-360, but this is an interesting thread to gain a bit more insight.. My hope is to get it a close to original, which may take a few years.. Thank you all for sharing and caring!
Sneezles61

Working at a Yamaha dealer in the 70’s we had t-handle Phillips (jis) screw drivers, I believe they were from Yamaha. I remembered they worked great and cammed out. 


 

I have a ton of money tied up in Snap On Tools. I need both a #2 & #3 JIS sockets for my 3/8" Hand Impact. As I too, will be drilling and/or chiseling two Stator fasteners that really should have come loose with my good stuff. But they didn't ...

 

For those of us in the UK, Yambits to a six piece JIS set - sizes #1, #2 and #3 in two different lengths each, 1/4 inch drive and fit into a magnetic T bar.

Asco,  save yourself some grief and buy a good Vessel Impact Driver kit.  I have the Snap on driver and bits...  bits are not only expensive but they shatter.  Yes, they replace for free but not fun to hunt down tool truck and then sometimes wait until they order the bit.  Bit is held into socket part with a small roll pin...  they just replace the bit, not the whole thing. 

Caveat is my experience is a few decades old...  maybe they changed something by now.  Bits I have are gold colored (or coloured so Uncle Al understands ) in a chrome 3/8 drive socket.  I still have a broken one I never got fixed.

Vessel drivers are excellent and the old metal box kits can be found used on ebay cheap if you're patient.  The fancy new Vessel kit comes with long and short bits and a nice rubber grip that helps protect the hand from a hammer blow.

Im not sure that this is a factor, but you can torque down an allen head bolt a lot more than a JIS or phillips.  I'd be careful when using allen heads on the aluminum cover plates. Sometimes cast parts crack easily in my experience.