It may not be anything, but I had an LT50 with similar symptoms, turned out to be the float level so low that it hardly allowed fuel through the needle. It would run fine until it used the fuel in the float bowl then stop. Once enough fuel had dripped in, it would go again.

 

I didn't get a chance to mess with it last night, but plan on pulling the pipe off tonight and cleaning it out and inspecting plug wire and cap closer like LT80 suggested.

Merryman, it does act more like your issue. It seems to run out of fuel. I have been looking else where since I thoroughly cleaned the carb including boiling it. I will pull it again and see if I can find any issues.

 

If it is the float, I hope he has a float with the metal tab.

 

No, I have the plastic tab on the float... I pulled the carb and cleaned again, floats look OK and do not have any fuel in them. Took a butane torch and heated pipe and blew air threw it with my small compressor, nothing noticeable, and inspected plug wire and replaced plug with new one. No change. Here is a video of what it does. Sorry for the poor footage, but best I could do at This time!
As you can see it starts fairly easy and will rev to the moon for a few revs and then it acts like it runs out of fuel. I'm starting to think carb is bad...

 

Have you taken fuel line off to see how the fuel flows out of the tank or tried running on prime if it still has factory petcock.

 

LTGranddad I replaced the factory petcock with a new banshee one. Fuel flows good out if the line. However, I did pull carb back off, just to see if I could see anything I might have missed. I did notice that the brass fitting that the float valve rides in was bugered up a little. I guess from previous owner trying to remove. Not sure if that would effect anything as the valve slides up and down easily.

 

Seeins you still have the cover off, when it shuts down, try to move the fan by hand to see if there is any drag.
You may end up taking the head off to see if there is something going on in there. The head gasket can be reused.
Does it do it with the air box disconnected?

 

LT, everything seems good with clutch, it pushes belt up front clutch face as I rev it. Free spins at idle and off. Does the same thing with Airbox removed. I actually replaced filter and cone the connects to carb and filter basket with new OEM.

I am beginning to believe it's the float. Starts good, revs for a min and then acts like it runs out of fuel. Let it idle for a min and it will rev to the moon again. Then repeats. But I'm not wanting to buy a new carb just to verify, especially when everything looks ok in the current one other than the brass insert a little chewed up like someone tried to remove it with needle nose pliers

 

What I was refering to was the possibility of the piston sticking.
I got another chinese cylinder sent to me. The ports are not chamfored on any of the chinese cylinders I've seen and the ports do not line up good at all.

As I'm holding the carb, I blow (with my mouth) in the inlet and work the float to see how well it's flowing. Maybe that can shed some light.

 

I chamfered the ports before installing.

I pulled the carb and was looking at rebuild kits and noticed that the pictures shows a rubber cap on the needle valve and mine doesn't have one. Would that cause an issue?