Kohler xt675-2047 NO MARK crankshaft

I can't imagine it's true that there's no mark, only perhaps that you indeed see it, but expect it to look differently, and so miss it. It will look like a little dimple punched into the metal. If your camshaft is plastic and has a little raised and painted mark, and you expect something similar on the crankshaft, you won't find it. Look for the dimple.
 
I don't see the video you refer to attached to your post. If you still can't find the mark on the crankshaft, take a picture (a still picture) of the crankshaft with the camera aimed at the face of the gear. Maybe even include the camshaft in the photo with both shafts mounted in the motor side-by-side.

From another website:
I will tell you on the XT675-2011 engines there is a washer that is on the crankshaft COVERING UP the timing mark!! SO BEWARE of that!! I'm betting this will resolve your issues finding the timing mark! As this fooled us as well till we looked into it more! Yes make sure there is no washer on top of the crankshaft as this will fool you as it covers up the timing mark!
 
 

Cant upload here:/

Yeah, I have to agree with you. I see some marks, but probably just reflections. So here's what I suggest:
 
1. Turn the crankshaft so the piston is at the top (TDC).
2. Look at the lobes on the camshaft and position the camshaft so that the lobes are at a low point when facing the lifters. Both lobes will point away from the lifters, but not directly away. If you imagine the lifters as being at 12 o'clock, the lobes will be one at 4 and the other at 8. I'm imagining the camshaft as transparent so you could easily look down at the lobes. Since it isn't, you'll have to look around the gear. There's probably not much room, so do the best you can. Consider marking the camshaft gear to sort of outline where the lobes would be if the gear were transparent.
3. At this point, you're probably properly timed, or close to it. Convince yourself by turning the crankshaft in the direction that it normally rotates (refer to the orientation of the pull cord, if necessary, to determine rotation). As you turn, the exhaust lobe will open the exhaust valve. Turn some more. The exhaust valve will shut and the intake valve will open. Turn some more. The intake valve will shut, and soon you'll be back to where you originally positioned it.
4. Check again. At TDC, the lobes should be at 4 and 8. At the bottom of the stroke, they'll be at 1 and 5. At the top of the next stroke, they'll be at 10 and 2. And at the bottom, at 7 and 11.
5. Now that you're used to examining the lobes and their relation to the lifters, look again to see whether you positioned the camshaft well enough. Maybe you can adjust it by one tooth one way or the other, and have the lobes closer to the 4 and 8 position I mentioned.
 
If you're not sure what I'm talking about, let me know and I'll try to include some drawings.

I don't understand what you mean by starting it with a screwdriver. You don't mean using a screwdriver across the terminals on an electric starter, do you?

Well, the only real difference is the speed, right? Does the drill have a variable speed? Try a slower speed and see if it again fails to start.
 
But now the question becomes why would we need to spin the motor faster to get it to start. There are a few possibilities, namely,
a) low compression, that is, bad rings, damaged cylinder, or valves not seating properly (see also timing below);
b) timing being off a little so that the valves are opening too soon, resulting in poor compression;
c) weak spark; or
d) poor fuel feed.
 
Can you get it to start with starter fluid using the starter rope?
When it runs, does it smoke (burn oil)?
When it runs, does the exhaust smell of unburned fuel?
Do you see any liquid forming (perhaps smoking) at the muffler?
Does it run well under load?
Considering that you were fiddling with the timing, that's the first trail I would follow.
 
Permit me to ask why you opened the engine in the first place.
 

You didn't mention the cylinder. Yes, you replaced the rings, but did you take measurements of the cylinder to see if it needs to be rebored? Rings are harder than the cylinder surface, so a large ring gap typically means that the cylinder is worn more than that the rings are worn. And when the cylinder wears, it does not wear evenly. One axis, the one perpendicular to the crankshaft, wears more than the other, resulting in an oval opening when viewed from above. Old rings conform to this cylinder wear, so you have oval rings running in an oval cylinder. When you replace the rings without boring the cylinder, you'll have round rings running in an oval cylinder, meaning you now have less compression than before you started! So what to do? You can take things apart again, measure the cylinder, bore it straight, use oversize rings, and congratulate yourself for doing the job right. You can also leave it alone, and run the machine praying that the new rings eventually conform to the oval cylinder. Since I suspect your problem at this point is cam timing, leaving the rings and cylinder as they are might not be so tragic.
 
You asked whether you need to reseat the valves. If the valves are good, no burned edges, and the seats are good, and you didn't mess up the mating surfaces when you cleaned them, you won't have to reseat them. But, considering the wear on the engine, and the reason you started this project, it wouldn't hurt to lap them and start with a nice surface. It's easy enough and can be done with inexpensive tools. For a perfect job, you would also check how the valve guides are holding up, that is, that the valves are not wiggling in the holes.
 
You mentioned that you tried to avoid the spot where, at the top of the exhaust stroke, both valves are slightly open. I'm not looking at your camshaft in front of me, so I can only guess, but I imagine that the lobes overlap a little. That is, when you hold the shaft in front of you so that the two lobes are up, you'll see that they are not positioned so that the valves are fully closed. They are not flat across, but bulge up a little. (Let me know if you need me to draw this for you.) This is normal. The exhaust valve typically starts to open just before the piston reaches bottom, and is still open a little when the piston reaches top. This, of course, is a big issue when dealing with race cars, where one tunes the cam lobes to achieve the wanted performance. On the lawn mower engine, the manufacturer tunes for one speed, 3600 rpm. He doesn't worry about low end torque, or acceleration. Nowadays he probably cares more about his emission rating than anything else.