Expanding on Rufus13 String Test

Your rear wheel is centererd in swingarm by axle cams
Your Transmission and engine are centered in swingarm by swingarm pivot bolt
Your swingarm pivot bolt is attached to the frame each side of the swingarm in heavy rubber blocks that allow vehicle alignment
Your vehicle alignment is controlled by the engine front motor mount at the front of the engine down by the voltage regulator and oil cooler.
You also have a top engine mount that controls engine, Transmission and Swingarm tilt in the frame

Research Vehicle Alignment your Model and Year

Now back to Rufus13 string theory.............I have used a cheap motorcycle jack from harbor freight having a rectangular top plate that allows holding the bike up straight while weight is still on suspension. I useed to car jack stands a few feet in front of the front wheel. Tie the string to a stand, walk the string around the back tire then back up to the 2nd stand and tie it off. Get the string as high as you can on the bottom of the back tire and as high as you can on the bottom of the front tire then move the jack stands to a point where the string just touches the front and rear of the back tire. That should place the string just touching the front and rear on the front tire. If you can't get both sides touching front and rear of both front and rear tires your alignment is out.

I 1st started doing this on an early rubber mount FXR so that front tire was smaller in width than the rear. In that application you simply measure the string to the sides of the front tire to find if the front wheel is in the center of the strings.

AGAIN, Research Vehicle Alignment to understand your rubber mounted harley davidson

 

Wish I've had that option (to just swap a wheel to try) and thanks for the really generous offer !

 

Thanks for suggestion, while it's good and I'll definitely do research on that what puzzles me is that prior to the flat tire I didn't have any alignment problems - triple digits and bike was stable, now 70-75+ and it feels like, I don't know, losing traction or something. My son was riding behind me on the test ride and noticed my rear end was starting to oscillate side to side and effect increases with higher speed.

 

I read you herd a loud Pop, then rode another 1/2 mile finding tire still was over 1/2 full at 20 PSI

Loud pop tires go down to 0 PSI immediately and you fight to maintain balance until you can get it stopped as soon as possible.

Are you sure loud pop wasnt 1 of the vehicle alignment connections? Doesnt take an engineering degree to look.
If I were you, I would check;
1 - both ends of the top mount below gas tank left front as sitting on bike - everything tight?
2 - Front motor mount & Alignment assembly, center of frame down by oil filter - everything still tight?
3 - Rear swingarm pivot rubber blocks - below rear passenger floorboards, usually a football shaped plate with 2 large bolts clamping swingarm assembly to frame. - no missing bolts? I have on 1 occassion had 1 of the cleblock bolts bead broke off but I was carrying a passenger and had the front wheel in the air.

 

What caused the blowout? I’m no expert but my bet is something structural is causing the rear tire to run wrong, heat up and blow. I would be focused on welds, bushings, bearings, fasteners, alignment etc etc.

 

Were it mine, I'd raise the rear of the bike and be rotating the rear wheel assembly while watching and measuring. Looking for wheel and or tire runout, axially and radially.

I'm also willing to fire up and "ride" a bike up on lift with the rear wheel off the ground. I'd probably do that, progressively, watching and feeling for vibration in whatever direction.

I rather suspect you've a defective tire.

 

How's your FRONT tire?
A front that has lost it's profile and had a "flat" center of the tread can cause a wobble.

 

Few things
* Blow out and 20 pounds of pressure?
* Do not use balance goo - Its going to do nothing
* Did you have the issue before the tire went bad
IF NOT
* did the tire fail or did something cause it to fail
* was the mechanicals diagnosed to make certain nothing caused the tire to fail?
* if all is ok, is the new tire bad? What is the condition of the front tire? Are they matched?

Im not certain there was proper diagnosis done. Me, I'd start from square 1 and not trust any of the prior work...

 

Do you fell like you hit something in the road or did the tire just let go ?
What kind of damage to the tire ?

WP

 

It wasn't a blowout - I was going through the intersection, where on one side was some kind of construction, so chances are I ran over something from that construction side. The pop that I've heard not explosion type but something big punctured the tire.
While I was waiting for the tow I've tried to roll it back and forth to try and see if there's any foreign object; didn't see anything, neither did I see blowout.