Ok, so even if this bike was perfect it would die without some manual throttle while starting?
No. You still aren't getting it. With the PD style carbs you have, you shouldn't really need to add throttle with choke operation (although you can), as it has a fast idle cam that should open the throttle enough during start up for you. The fast idle cam is coupled to the choke knob and engages progressively whenever the choke knob is anywhere but fully pushed in. But, you can't simply pull it out completely and leave it there, as that blocks off incoming air to the carbs. The choke operates similar to the throttle in that regard. When you start it, do you open the throttle all the way a hold it it in that position after it starts up? Or, do you back off the throttle as soon as it starts? Choke is a similar technique. Out all the way to start and then apply only what is needed to keep it running. (earlier Cb550s did not have a fast idle cam and required the operator to hold the throttle above idle position during warm up. But, you STILL didn't leave the choke lever full on after starting.)
Why don't all carbureted bikes act like that? For example, that KLR in the background.
You are looking at nearly 10 years of carburetor design changes. By 1987, carburetor designs changed.
Most went with different cold enrichment schemes than the choke butterfly plate technique used on the SOHC4.
There are thousands of different carburetor designs. I don't understand why you would think they would all operate exactly the same way.
There are thousands of motorcycle designs. Do they all operate and perform identically?
Different machine designs exhibit different nuances. Carburetors are machines, too.
I had a 1937 Chevy. On the dash was a choke knob AND a throttle knob. Both the choke and throttle knob had to be used and modulated for starting and during warm up. The fast idle cam coupled with the choke was a later development in years that followed, still operated with a choke knob. Then the thermostat operated the choke and fast idle cam became standard. Later computer controlled fuel injection, using temperature sensors made operation a simple turn key process.
The computer on the 78 CB550 is normally perched about 2-3 feet above the seat. But, the efficacy varies with the example.
