Tank you for the comprehensive write up. Just got of the bike. Starts instantly at freezing temperatures, and idles like a sawing machine. No backfire. It happens when hot. I dubt there is an exhaust leak (logically following way I assembled it). So... definitely something with the #3 carb. And it happens only an very aggressive deceleration. Shifting down with smoother throttle backing off has no effect. It seems like it happens in the 15 - 20% of the heavy engine breaking whule hot.
I am kind of thinking swapping carbs when the #2 is fiering? I might invest in a set of pods for easy carburator exchange. I dread the seals of the stock set up! Proverbial bitch!
You are absolutely right. Yes, in a way, I've been hoarding KZ1300 stuff. But that's only when the price and opportunity was right. ANd I am paying for this right now through my nose (cc card debts). BUt I am after Aa bigger pic. The imge of another 1300 beautiful and running. I just must do that.
I will follow up on the backfire thing. Seems like not a naging thing, but I want the bike to run perfect! Well, just an hour ago when I took it out again it screamed!!! I did the rear wheel wiggle accelerating, and in general - it's a very comfortable power house.
I do have actually decades of practice, and I always make safe home. The fine detail that people don't know is, while they have 4-5 beers, or scotch, I have 4-5 gallons. Things can get blurry at those speeds! hahaha