Honda question about idle surge

[MATCHBX]

Running at 2000rpm at cold start up is normal for a Honda. After it warms up it drops down. It should idle around 700-800rpm.

If it starts idling up and down more than 500rpm after it's warmed up, it is usually a sign of air in the coolling system. Usually caused by a bad shaft seal in the waterpump or a bad radiator cap. I have encountered this problem in my Honda as well over the years. They can sometimes be a pain in the butt to get all the air out after changing thermostats or draining the radiator and refilling it.

If left to run like that for about 10 or 15 minutes, it should start overheating. Next time, just because it's revs at 2000rpm at a cold start up, don't rev the piss out of it to try to get it down to a lower rpm. You'll do more damage than good. Next time let it warm up to operating temp before you starting raising the rpms.

Edit: I know you said you slowly revved it, but you shouldn't ever rev a cold engine so high until it warms up.