Motorcycle shuts off when you give it gas

This is usually a sign of a lean mixture in any motor. An engine requires more fuel when cold because the fuel doesn't atomize this is why they have a choke and why you smell raw fuel in the exhaust then a motor is cold.
So my guess would be you have a partially blocked main jet, a blocked choke port or a vacuum leak somewhere and it is closing off when the metal expands. If the carb has a mixture screw that may be out of adjustment also. Some have them some don't.

The most common is a blocked port in which case you pull the carb and disassemble the whole thing and then jet carb clean through each port watching the exit to make sure you are getting good flow out of it.

Hope this helped.

Rich

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