Boule, the correct Phillips tip is the #2.  The #3 tip is too broad and won't even get started good in the JIS recess.  The #1 is way too skinny to engage anything -- so #2 is the one you want.


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Here is an "advanced" trick that I can do easy-peasy that would foul up for you likely every time you try it until you could practice it a bit and get the feel and hang of it.

Ya got a buggered up head and NO REPLACEMENT FASTENER available any where in town (and yep, I have  been there before and I didn't want to wait 10+ days to get a replacement screw from California) ....  

What to do when you got nothing to work with but time and some good tinker skills?

Why, take you a round flat tipped punch and angle it in towards the center of the four part apex form on the buggered stuck screw head and tap it lightly with a hammer to reform the torn up soft metal into a somewhat rounded looking head form again.  

Reangle and tap, reangle and tap, reangle and tap, reangle and tap, reangle and tap .... repeat as needed.   Repack from the outside all those protruding metal tips back in and repack/reform that head until it looks like a screw head again.

Unfortunately, this cold forging closes down the apex form so you can never get a #2 phillips screwdriver tip down into it again since you mashed everything in towards the center in an uncontrolled fashion.

But you can get a #2 tip end started somewhat -- so you take your long #2 Phillips tip from the impact driver set and you tap it straight down into the mashed down head form with light taps from a heavy hammer.  The bit jams tight of course and sticks going in of course but you tap it on in anyway, leaving it firmly stuck.

You check the rotation direction on your impact driver again (they really do occasionally cam over unexpectedly when smacked and go backerds to what you are wanting for an unscrew), then you gently fit the impact driver on to the stuck #2 long tip that is wedged in your reformed screw head.  Grip it firmly and do a few practice swings with your heavy hammer.

SWACK!! goes the hammer.  

It always breaks the screw free, mainly because you shocked the stuck threads pretty good doing the head reforming banging action and you stretched things a tiny bit on the rebound when you tapped the #2 bit straight down into the head form.

Plus you just swacked the heck out of a perfect cold formed fit up to a now US standard #2 Phillips head screw and all the torque went exactly where you wanted it to go.

Don't forget to spray a little aluminum paint on that reformed screw head you just remade while you have it out -- it will rust otherwise.

Yep, you jest made a good fastener again out of a buggered useless one  -- one that can actually be reused.   You also work hardened the soft jap steel somewhat, so it is now harder to strip out now than it was originally.  

Plus, it IS a US standard #2 Phillips screw now.  
It fits all your standard stuff perfectly now.

IMPROVING THE FIT OF A #2 PHILLIPS IMPACT DRIVER BIT IN JAPANESE MOTORCYCLE SCREW HEADS

I tried this thought out on my most worn #2 (American) impact driver bit tip and it improved things quite a bit.   It is a skills based mod, so do it at your own risk.

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Issue with #2 USA impact bit tips in motorcycle screws is that the tip bottoms out in the recess with a little bit of slop to the flute engagements.  It strips easily as we have all learned the hard way.

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I touched the very tip of my #2 impact driver bit tip to my belt sander, very carefully removing a small amount of the tip material all nice and square to the length of the bit -- while comparing it frequently to a new JIS screw head that I had handy.  

My goal was to remove enough of the pointed tip to so that the flutes engaged 100% and held the ground tip portion of the bit slightly up off the bottom of the recess.

It worked to improve the engagement when driving -- what actually happened was that at the first blow the forces were totally transferred to the flutes, reforming them to American standard #2 format and the tip was driven down to seat at the bottom of the recess.

The screw backed off and did not strip (and that is an improvement in my eyes).

Now to be completely precise, I reformed the screw head to the bastard format of the modified #2 bit tip that "made" the new form.  Now an American standard screw driver bit doesn't fit exactly and neither does a JIS screwdriver.

But if your goal is simply to get them out and replace them with allen heads, it is a workable trick.

I taught an old Jack-of-all-trades this trick. He'd never heard of that idea. It works every time!