I just resurrected (an orange) '79 Express from 22 years in a garage. I was giving up after a dozen or so attempts where it ran a little, then sputtered out. For what it's worth, here are words of wisdom from Jax184 that helped me (the part about not losing patience when it's sputtering out...it's actually warming up for the long run you're hoping for.
From Jax184 on 9/14/04:
"...I have noticed that the Express is
A) Very very very picky about it’s carburator
B) Very very hard starting until you spend a few weeks/months going over it with a fine toothed comb.
I never did narrow down exactly what made it act that way…
The best advice I can give is to stick at it, set the carb settings and make sure you have a good air filter.
Then get the bike running and let it sputter out. Repeat a dozen times or so.
As the bike warms up it becomes more flexible to the possibility of actually running.
Eventually it will reach a point where it doesn’t die and will actually let you set the carb settings right.
From this point I’d suggest riding it a bit to burn out the oil that’s collected in the crank case and get everything moving again. This seems to have helped mine quite a bit.
I’ll admit that even my bike is a pain to start at times. It has even been known to conk out at random intervals for seemingly unrelated reasons. But hey, it runs well most of the time. All in all to me it’s worth it.
Plus it’s still cost me less then $200 including the cost of an entire second bike for parts."
And finally, my "play-by-play", in case any of what I experienced can help you. Particularly, I mean taking the air cleaner off (temporarily) and putting your hand over the air intake, as sort of a "super-choke", until it gets warmed up. I'm an inpatient type, and though it takes a minute to take off the air filter cover and put it back on, it's one way I've found to cut to the chase and keep the thing running long enough to warm up so you can turn of the choke and see how it's really idling. Mine must warm up for a few minutes, with after the choke can be turned off, before it'll accept throttle and become ridable.
From me on 9/23/04:
"My screws were originally 4 turns out for the Air Mixture Screw and 1 1/2 turns out for the Throttle Stop Screw. I re-set them per Jax184’s LONG version instructions (AMS 2 1/8 turns out, and left the TSS at 1 1/2 turns out). I started with the choke full and the air filter off. After a few sputters, I seemed to get better results with the choke open about 20%. I played with the screw settings a bunch, finally ending up with the AMS out 3 turns and the TSS out 2 turns. By now, that marmup/flexibility he wrote about was apparent (2 hours into the session). My screw adjustments may not have mattered as much as my next move, instinctive and reminiscent of dinking around with old Lawn Boy Mower carbs in the sixties. I covered the air intake with the side of my hand, and she started to come to life on the next start. After doing that a few times, I realized I could put two fingers of my left hand over the intake, and move one finger on and off the intake, which kept it going and gave it a throttle effect with the air. I gradually fed it more