Thanks, Maxwell but I did that and instead of gas leaking from carb vent it shot out of the barrel of the carb

Any very small leak between tank and pump can suck air instead of fuel, even if it doesn't leak gas. Also, just because a pump is new does not mean it is good. I ahve had many new bad parts over the years. Bad gas cap that should be vented can also cause issues.

Common leak. You will need to use epoxy or some other sealant to fix it, JB Weld for instance. You might have to strip down the carb and clean away fuel residue etc for it to take

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/joseph_f4ed739f62995525

check for fuel leaks. from the gas tank, to the fuel lines, to the carb. i assume its an electronic throttle body 2 barrel. i have seen those leak internaly from the inside of the carb/throttle body causing exsess fuel to be used. you could also have a very bad fuel/air ratio going on there. could be bad o2 sensors. but i would start with the leaking fuel first.

Check that the vent hole in the cap isn't obstructed.

--W/D--

sounds ilke a ai leak the manifold block gasket may be leaking or a crack in the carb to barrel insulator- or it has a torn / perished intake boot or the impulse line is perished , could even be a loose barrel and the base gasket is leaking - or leaking crankcase seals

you have ruled out secondary compression and spark and blocked muffler

only proper way to know is to remove muffler and carb, block off both
inlet and exhaust with rubber gasket and a metal plate - make sure the inlet metal plate has a access hole for you to pressurise the c/case
remove clutch starter assy and flywheel
set to psiton to tdc and pressurise the c/case to 7 psi
brush around seals and gaskets with soapy water and see where bubbles are comming from that will be your leak it may be quite substanicial - check main seals, c/case joints, manifold block carb end and cylinder end and of course the manifold block itself

2 strokes need a air tight c/case to operate to fuel pump in the carb and to pump mixture from the crankcase to the cylinder

if sucking air instead of fuel they can be really hard to start, stall alot , have no power , will not idle , and seem to overspeed and get very hot
not to mention can damage tp piston and cylinder

have a look or let your local shop take a look for you

cheers

it's probably leaking from the carb and down the cylinder into the crankcase.
it is probably due to a stuck float in the carb. take the float bowl off and make sure it is clean. the float can also be full of gas not letting it float up and stop the gas flow. the carb will fill up and leak wherever it can which is likely the case

Just a shot in the dark here. Mikuni carbs were problamatic on that engine. I remember them well. They had internal vacuum leaks and diapragm leaks just like you describe. I dont kn ow if you can get it any more but the fix used to be a new reman carb. they were not rebuildable. But I always wondered why you coul not have a base plate adapter made by a machine shop to adapt any other simpler carb to it? as long as your cfm rating was the same--ya know? Like take a holley 2 barrel off a k-car and adapt it on. Anyway I hope I helped. But that is what it sounds like. Carb replacement. Thanks