Check the vent hole in the fuel tank cap to make sure it is not clogged before resorting to more drastic measures.
My thinking is that clogging of the fuel line would not correct itself during a 5 minute wait. A clogged cap vent by contrast would behave exactly like you are describing.

Was the filter changed after you cleaned the tank?

Yes, the gas filter was changed after the tank was cleaned.

ditto mownie's fuel cap vent advice..

Injun have fuel pump?

Yes, it does have a fuel pump.

Eliminate the cap problem first by waiting till the problem happens, then loosen the cap and see if it will restar without a delay. If so, clean the hole in the cap with some wire and you should be good to go.

If the problem is not the cap then check the following:

Turn off the fuel shut off valve. Remove the fuel pump end of the fuel line and direct it into a can. Open the valve and see if you get a steady stream of fuel into the can. Observe if any debris is present. Reverse the above to put this back together.

Next disconnect your spark plug wires and then remove the carb end of the pump to carb hose. Put a tray or can where it can catch the gas. Crank the engine. You should see regular spurts of gas going a good distance from the end of the line. With a gloved finger try to cut off the stream and it should spray (like what happens when you put your thumb over a garden hose.

If all the above seem fine I would put an in-line spark checker in series with the spark plug wire(s) and see if it stops or becomes erratic when the problem occurs.

Best of luck. Let us know what you find and we can direct you further based on the tests so far.

Thankyou all for the responses. Note that the engine does not stall- its power(RPM's) drop cosiderably- but it keeps running (slow)

Checked the gas cap. Vent is totally clear.