Screw This (JIS Discussion)
 

I'm aware of the JIS issue with our bikes, and the service bulletin mentioned in this thread...

JIS vs ISO Thread Pitch

I recently obtained 5mm JIS screws, but they are "new JIS" .8 pitch instead of "old JIS" .9 pitch. Fail.

I'm missing 1 bloody screw for my "front winker". And, I wouldn't mind replacing all of my handle switch / winker screws just for appearance, but that's not mission critical.

Got together with a machinist friend who has a whole shop at his disposal, and after he did some calculations, he thinks a 12-28 screw run through an M5-.9 die might do the trick. Unfortunately, he doesn't have that die.

Before I try that experiment, which involves buying that die, does anybody have any experience with this issue? I know it's pretty whacky to go through all of this for 1 screw, but I like doing things like this just to know I can, ha ha.

I suppose the more sensible solution would be to find out if anyone has a source for "old JIS"?


On another note, I recently ordered the engine screw kit from Rimfire. I hope those have correct pitch (?)

Your engine screw kit should be fine.

In a few cases I drilled and re-tapped the holes to accept a standard ISO metric thread, but I opted not to do that with the rear winker lenses, and spent $12.99 (plus $5 shipping from the other side of the world) for 4 skinny JIS screws, just to have the right parts.

I have no experience with JIS dies, although I recall there was a company in Europe that sold JIS sets. Seems like a high price to pay to make a single screw.

I can get a single JIS M5 x .90 die for $11, and then I could make all the M5 screws I wanted. Looks like a fellow could get rich doing that Ha ha.

On further research, I see the engine screws are all M6, and that pitch did not change between old & new JIS. So, that's why the Rimfire kit will be ok. Although there are two M5s for the left cover.

Well, that was easy. I received my M5x.90 cutter, ran my "modern" JIS M5x.80 through it, and it fit perfectly.

For fun, I ran a #12-24 through the cutter. That fit too.

So, goodbye skanky old screws. I can now make my own pre-67 JIS M5s!

I imagine that a few threads get sacrificed in the process ... can you post a pic of what the re-cut screw threads look like?

Attachment 793

Original, M5, #12

This image makes the M5 look like the threads are not substantial, because it's so new and shiny, but they are.

These are the very first experiments, run through the cutter, and with no other cleanup.

All three have the same "feel" going in, are not loose, and snug up with a natural feel.

Attachment 794

Received my RimFire kit as well. Well put together... very pleased.

And I now own actual JIS screwdrivers. No more buggering up the screw heads on my old bikes.

Attachment 795

Thread gauge fits

Look like a winner.