90 viper running issues

[ninja11zx]

Have a viper 90. not sure the year. Its a 2 stroke. wouldnt start pulled carb and leaned . it was clean anyways. installed new plug. will start right up then idle for a couple minutes then die out. what else to look for. thanks

[LT80]

Check the compression.
There is a screen in the silencer that tends to goo up too.