Furnace flames cycles off before temp is reached

I'd use a meter and determine what's doing the cycling, first, stat or hi limit. Check the temp rise. I've never had short cycling problems with my RV furnaces but I like to see no more than 70* degrees rise in a res. furnace, when the airflow is really good. Make sure the flex ducts aren't kinked, stat in warm air current, clean the blower wheel, dragging motor, etc... normal checks and maintenance. Craig