If it ain't broke, don't fix it!

 My CT1 was running fine, then I decided to clean the carburetor in an ultrasonic cleaner, and dried it all thoroughly. Everything looks spick and span, put it back together and it ran great, until it didn't. It was idling a bit faster, so I backed off the idle screw a little bit, and went to bed.

Next day I was going to adjust the air screw a little bit, but I can't even get it to start now. Took carburetor apart, checked all the jets and cleaned them again with B3, everything looks great. Removed the choke plunger, and cleaned that out again, even though it looked fine. Ran B3 through every single passage and they are all clear. Put carb back on, still not firing up. Not even trying. Went back to one and a half turns out for the air screw and idle screw, still nothing. By the way the little carburetor bowl o-ring is in place, and new.

I was getting good spark on the spark plugs, but they did have some carbon, so I cleaned them in the ultrasonic cleaner and thoroughly dried them with a heat gun, and they look brand new now. Still not running.

 Pulled off the inline fuel filter and put a new one in. No difference. I'm getting spark, I'm getting gas, and I didn't do anything to the timing. Spark plugs are gapped about .022, and again I get a very bright spark. I am stumped. Just hoping someone here can come up with something obvious that I'm not getting.

Are you trying to start it with the key in the second position for lights on? If so, try it in the first position.

My twin to your bike won't start in the lights on position, and if I am riding it and switch over to lights on it dies.

I haven't begun to troubleshoot it yet....

Thanks for the suggestion Schu, but I've tried it in both positions. By the way having re-soldered the red wire to the underside of my ignition switch, your problem might be that you don't have a good solder contact with one of the spots. The red wire solders to two contacts right next to each other, one is for regular and one is for running lights. However before I cleaned the carburetor, I would run it in either position with no problem.

Here's a video of my spark.

Is plug wet with fuel?

My first guess is flooded.  Had that happen SO many times when I was a kid.  Usually because I forgot to turn off petcock. 

Also might try new plug.  Plugs can spark outside engine and fail under compression. 

At first I thought it might be flooded, but since I've cleaned the plugs, when I try to start it and then pull the plugs, they're just barely wet. Have a brand new petcock and I always make sure to turn it off, and it turns off well. I just opened up the carburetor again, and I still don't see anything, maybe there's something I'm missing with the choke plunger? By the way one of the plugs is fairly new, the other one is 50 years old, but I've been using the new plug. I may pick up some new ones tomorrow.

"barely wet" = flooded in my experience. 

All the jets are in the carburetor, and it's basically the same as it was before I cleaned it. I assumed a little bit of wetness on the plugs was because it wasn't firing up, even though I'm getting spark. Is the rubber boot on the plunger critical? It does seem to seal but is not super tight.

  

It'd run even without a carburettor if well flooded up but i wouldn't recommend trying--well i did as a kid & ran away till it stopped haha. Did it flood up overnight with fuel left on & a slight float valve fault. Just hold it on full song & she'll light up.

No, rubber boot isn't crittical from a running point of view. Does a good job of keeping dirt out that might make the choke stick or not want to close. Return spring looks good--you're lucky as rust an crumble.