I start mine at idle, small puff of black, as soon as idle settles down, 10-30 seconds depending on temp. I drive it out of the shed and what I do next depends on what I am going to do with it. If I am going to ask it to work, I let it run for a minute or two before starting, and I start gently and don't ask full power until it is fully up to temp. It warms up much faster if being used a little. If I am just going to use it as a powerful wheelbarrow.. then I just go do it. When heading 'back to the barn', I tend to run it at about 1200 rpms. Then I idle it down and put it away while in low gear. This gives it cool down time, and makes sure I don't hit the ROPS as it misses by less than an inch. If I have the chains on and they are in the wrong position.. I can hit the ROPS.. it is that close. New pole barn in the planing stages to fix that problem.
