I'll let you know. My Grandson and I plan on doing the Mt. Washington auto road in a couple of weeks.

 

I did the Mt Washington Auto Road during bike week in 2012 when I first got mine. Even with only bikes on the road it was a bit hairy. You realize just how wide the trike really is. I would never do it on a trike when the road is open to the public. Something about a cager not paying attention coming down the mountain at you; and, no guard rail on the uphill side.

You will find out real quick how good your tune is. Mine didn't ping too much but my oil temps were a hot 350* when I got to the top.

 

You can't move enough air over the engine due to the slow speeds, plus the load pulling the steep hills is rough on an air cooled engine. Each time I've been up the auto road I've been in one of the nice air conditioned vans.