I have a 92 lude h22a swap. durring the summer months it starts and runs perfect but every winter I it start it and want to shut off unless you hold the gas at 1500 rpm for at least 30 seconds. also I noticed that if I hold the clutch in its less likely to shut off.

 

It's spark or fuel related. Do a tune-up and see if that helps. Replace fuel filter, and spark plugs/wires for sure.

 

Remove the idle air valve then spray TB plate cleaner inside and let it sit for a couple of hours so it brakes down the carbon.You should be fine after that also clean TB as well.