Having trouble with my CT1C - at this point it won't start.  A month ago I was able to get it started, but if I let the rpms go below 4000, it would die.  The bike has been sitting for almost three years (a nasty shoulder surgery that went south) and I remember now that when it was running back then, you would have to keep it revved a lttile or it would bog way down - I replaced the piston and rings back then as well.  I'm wondering if it's possibly an air leak in the cylinder.  The carb is good for sure, it's the original Mikuni and I had a very reputable member here go through it for me just recently.  It's getting gas, the air filter is clean, and it's getting spark.  It has the original oil injection installed and it works.  The bike has not been abused and is very original.  I'm just trying to figure out what to check next.

I dont think your head is leaking. Usually if you have an air leak it wants to rev up more because its getting too much air causing a leaner condition. Its hard to say without hearing it in person but from what i can tell on this end it sounds more like its flooding out. Make sure your choke is off, my friend always gets his backwards. If your air filter is soaked in too much oil that could choke it out.  Are you sure the jetting and float height are correct in the carb? just because its been cleaned good doesnt mean it has the right jetting.
Is the air mixture screw turned out 1.5 turns? thats typically where its set at and then you play with the idle screw that raises and lowers the slide. The exhaust could also be plugged as well. Does it smoke a lot? a leaky clutch side crank seal can cause running issues. Did you measure the oil injection output? again if its getting too much oil it can cause issues. Like i said its hard to tell without actually hearing it but hopefully something here is of some help.

I will investigate those, thank you. The carb from what I can see is spot on but I will check it as well.

Have you done a compression check? If so, what is the compression reading?

If the pilot jet isn't blocked then I wonder if it's pushed out the crank seal behind the mag. If it's the other side seal it'd smoke worse than a chimney.

Dan retorque your head I’ve had something similar on a rebuild wouldn’t start the next day I heard a slight hiss and a retorque fixed it

I did retorque my head, and they were just a bit loose - they took a half turn or so. But we figured out what the problem was and I feel kind of stupid now. There was gas getting to the carb, but not in the carb - it turns out that the needle jet that lets gas into the carb was stuck closed. We took the bowl off and unstuck it, and the bike fired right up! Matter of fact, it runs better than it has for a while, since the carb was just rebuilt. If it happens again I'll know exactly what to do. Hopefully it won't stick on a regular basis; so far, so good. Thanks for your input.

Unusual thing to happen but that old yamahas for you always expect the unexpected.
With the head bolts, half a turn is a long way to need to tighten, so hope you've achieved a seal.