Carter 250 won't start

[Dallastx]

I've had the gtr running great for a while now. It's a fun buggy for sure. The last time about two weeks ago we took it out and it took a while to start. I thought maybe because it hadn't been ran in a week and a half and the fuel filter was empty so it took a bit to pull the fuel up. Then it ran great. A couple of days ago I was going to take it out again and could not get it started. At all. Before I had to feather the choke on the initial start of the day. Anytime after that it would start at the bump of the key. But now I can't get it to run. I tried spraying carb cleaner in carb but got nothing. I have spark. I have checked tdc to check timing and the marks on the cam and the opening on flywheel line up. The intake valve lash was closed up so I set it at .004 hoping that was my issue but when I out it all back together still no fire. If I hold my hand on carb opening I can feel suction and hand gets soaked with fuel. All jets are clear in carb. However the spark plug never gets wet. Seems as though I get fuel to carb but not into combustion chamber. I tried renting a compression tester from auto parts store but couldn't get a reading. I think it's defective though because I tried getting a reading from a quad I have that runs great and only get 20 psi intermittently. But zero movement of the dial on the carter. So I looked up about a leak down test. I took the hose from compression test kit and hooked it up to a valve and regulator and hooked it up to spark plug hole with spark plug adapter. With engine and everything at top dead center I opened the valve just enough to start hearing a hiss coming from exhaust pipe. Nothing from carb opening or from oil fill plug. If I understand what I read it means I have a leak in my exhaust valves. The exhaust valve lash was good though initially. It is set at .005. Does this mean I need to replace head gasket, whole top end, or is valve stuck and is there a way to free it up without tearing the engine apart. Or could it be something as simple as a bad CDi again. Thank you in advance. This site has been great at helping me out with this buggy. I really appreciate all the help.

[Dallastx]

I apologize but I made a mistake in my tests. When I could hear a hiss from the muffler and exhaust it was because as I filled up the chamber with air the piston pushed down slightly and was no longer at top dead center. After redoing the test and makin sure I kept the camshaft from turning I no longer had air escaping through the muffler. However, I do feel and hear a hissing sound coming from the exhaust valves/ springs/ (4 valve head). But only from there on the top side. Nothing from intake side. I hope this better explains my situation. Thanks.