Update: still have a nasty speed wobble anything over 70 in a straight line, like getting slapped from side to side constantly. I’ve gone through every check in the manual at least twice and still not making headway. Yesterday I pulled the rear tire and tried remounting it in a different orientation to see if the 2.5 oz was effecting it, got it down to 1.0 oz of weights. Again, no effect...

Tomorrow I will remove the new rear tire and mount up the old one and see if that does anything. I hope it’s just a bad rear tire and I can get back to riding again!

 

Wobble solved! It was the brand new tire; the clapped out metzler I took off ran straight and solid up to well beyond what a sane person would ride it. Now to get Avon to warranty the tire and send me a new one that isn’t messed up.

 

Good find.

 

Glad you found your problem.
I had the same issue with a new Avon Cobra front tire.

 

Glad you found it, but Sad Avon was involved

 

I was surprised as well, it’s a Storm 3D XD-M (71W) so wanted for 168 mph. The storm is b/o until may/June so I ordered a Spirit ST to run while I wait for Avon to warranty the Storm.

 

Well, the Avon Spirit ST arrived, put it on, and… the wobble is back

At this point I’m pretty much down to not being able to run radial tires, because there is no way that 2 different models of Avon 150/80-16 radials would both have the same manufacturing issues, and the wobble stops with a bias rear. Plus I’m getting sick of dumping money into tires for a bike that I can’t ride

I ordered a set of Pirelli Night Dragons, because they are the stickiest Bias tire in my sizes I can find, hopefully I’m done after that. I don’t know why the radial tires are an issue, perhaps it’s the particular geometry of my bike, because the sizes are a less than 1% change from the OEM rubber.

Back to the ‘fun stuff’! I ordered an Intellitronix Universal fuel gauge and swapped it out. Figuring out the wiring was a little tough because the ‘99 is different than the 2000+, there are 3 studs that the gauge slides down on, the left top left is the signal, bottom is the ground, and the top right is just a locator.

 

Not that it's a huge issue but the 2 models of Avon tires you used are not recommended on a 3" rim, both have a recommended rim size range of 3.5" - 4.25" and are not "RF" reinforced.
I ran proper fitment Storm 3D XM 160/70 R 17 RF on the rear of my raised Ohlins/rear, RT/fork equipped softail and it was one of my favorite tires.
You might do better with a proper fitment 150/80 B 16 RF Cobra or Cobra Chrome bias ply. I'm guessing you are going for grip...Cobra has significantly more grip than a Night Dragon.

 

@R_Einan Motorcycles and woodworking. Two of my favorite hobbies. I spotted the Powermatic jointer in your first post.

 

I feel like the majority of speed wobbles come from either the tires themselves or the PSI