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Well I needed to heat cycle it and torque the head nuts before I took it out. At least that's the way half the people out there do it. No more heat than running it on the street. I am aware of the glazing issue; from what I've found researching (and I'm by no means an expert, just going off the information I could find and what made sense to me) that's the reason for 2500 rpm over just sitting at regular idle speed so you have more cylinder pressure when you do that heat cycle. I know some people say go out and bang it immediately and some say baby it and there's a million different angles on break in procedure. The way I've done it seems to have worked fine, I've got good compression across all four.
But hey, maybe I can do it better next time!
What would be your recommendation, for future reference? And I mean this with upmost respect, but what sort of experience do you have with break in procedures?

When I'm ready to break in a fresh engine I make sure everything is ready for a ride, engine oil no oil leaks, air in tires, ect. I get my riding gear on roll the bike out get on the bike then start it and immediately ride it. I pre choose a route with no stopping and usually has a hill. I accelerate in first gear hard but not at full throttle or to redline. I'll roll off the throttle and let the engine braking slow me down to about 10 mph. I'll do this three times then shift into second gear and repeat then third, repeat, ect. By then I'm at the hill I chose I'll ride up the hilin third gear and accel hard. When I get to the top ill turn and start down the hill when I shift into third gear and around 70 mph I'll let the engine braking slow me down to about 10 mph shifting down as needed.
I then ride home home like normal park the bike overnight. In the morning re torque head bolts change the oil, do any tuning if needed then I'm done with break in.
My Dad taught me this when I was 12 and it worked on the thousand plus engines he overhauled and it's worked on the hundreds of big Kawasaki engines I've done. I've never had one come back and they all run strong and burn no oil.

Thanks Baldy110!

Similar for top-end ring job only?

I understand. I guess Ill have to keep that in mind for next time. I guess there's no real reason to keep it off the road for that first heat cycle; at least none that I know of. I was concerned about seeping oil without that second torque down of the head nuts. I'll have to get my compression numbers again when I'm back from vacation and next time I set some rings I'll probably do it your way and we'll see if we can't prove a difference.
I mean, who wouldn't want to get on their bike quicker anyways?
Good news is so far I don't see any signs of burning oil, but then again I'm only roughly 120 miles into the fresh top end.

Yes just like a top end ring job. I even have a case of break in 30 wt oil I use just for this. About 8 years ago I overhauled a GPZ1100 and used my usual oil for breakin Rotella 15-40 wt like I've done dozens of time. I went for my break in ride but I could not get the rings to seat, lots of blowby and low compression. Tore the top end off de glazed the cylinders and put in new rings. Use the same oil and my break in procedure. Again lots of blowby and low compression, very frustrating. Tore the top end off again de glazed the cylinders, new rings again but this time I put in break in oil. Did my break in and this time great compression, no blowby and ran fantastic.
Did a bunch of research and discovered the oil companies are making their oils so good it's not allowing a good bed in on the rings. The break in oil has no friction reducers its like the oil from 30 years ago.
I am curious where did you find the info to let the engine idle at 2500 rpm to heat cycle the engine? I've been building motorcycle engines since 1976 and have never came across that one.

www.kzrider.com/forum/2-engine/607610-st...engine-after-rebuild

There ya go, that's where i found it. Even on there it says 5 min so obviously 15 min was an exaggeration. Like I said I went off of temperature so my internal clock is a tad off.

Build it... Start it.... Ride it. Job Done.
Just don't thrash it or cruise at a constant speed/rpm out of the gate.
Use engine braking to push the rings into the bore.
No need for idling at whatever rpms unless you want to risk glazing the bores and no need to limit the max rpm's for any specific time or mileage period .

Yeah I was engine breaking as often as possible during those first 100 miles and varying my rpm. Maybe that was my saving grace as far as the whole glazing issue. Just made sense to me to heat cycle and get the head nuts torqued down properly before actually riding it.

Just remember for the next time, NO idling even a high idle start it and ride it. Also when you swap out heads be aware as you pull the old head off you will disturb the base gasket and could cause an oil leak. Whenever I work on a head I always remove the cylinder and replace the base gasket just so I don't have the customer coming back with a leaking base gasket later. I use that opportunity to de-glaze the cylinder and if the rings are good I'll reuse them. After getting it all back together I'll do my break in on the engine.

Like Baldy, I follow the same bedding In . I go for a ride and constantly torque the motor to 4K rpm . After checking the engine I keep on torquing now and then and prevent constant speed.
As stated idling to long glazes the bores/ rings. I never understand why riders (in Australia where its warmer) warm up the bikes every morning for 5 to 10 minutes or more.

When installing a freshly-honed cylinder block and new rings (top-end below the head only), how important for carb jetting and synchronization to be correct for startup and break-in?

I assume the previous carb settings will be close enough to start with, but for how long...considering the sync process may involve a period of extended idling time?

Unless you have some unknown combination of parts on the bike the jetting and state of tune really doesn't matter as long as it's ridable just ride it. Seat the rings then tune it later. Ive built some engines with wild cams, ported heads, big pistons, big carbs, ect. I tune the carbs prior to start using my past experience on jetting. It's not perfectly tuned but good enough for bedding in rings. The bike doesn't even need to idle correctly afterall no idling remember?
What a lot of people don't realize is you only have one chance at breakin. Do it wrong and it requires a top end teardown, de glaze and rings. No amount of riding trying to bed the rings will work once the cylinders are glazed. Like I mentioned earlier break in occures in the first 15 to 20 minutes of it running. That is a narrow window so if you let the bike just sit there at idle all your doing is risking glazing the cylinders. Do your tuning after break in,