My 2009/10 experience:

1. Iran: Escorts from Bam to the border (Zahedan-Taftan) for everyone (not just Americans). Pain in the neck because they grab your passport and go and assume you'll chase them. Not much you can do about it, just be ready to put up with it for a couple of days. They'll probably stall you to ensure you stay at one of their "safe" hotels close to the border, at fixed prices. Again, it's one night, they have the guns and the stamps, you just have to deal with it.

2. Pakistan: Escorts from the border (Taftan) all the way to Lahore. Professional, fast, excellent chaps throughout. Don't leave without them, don't be a I-know-your-country-better-than-you western supremacy traveller. They're offering a free service and are looking out for you. Take it. They don't force a ridiculous pace or anything - if you want to cross Balochistan at 90mph that's a bad idea anyway. Be prepared for constant riding throughout the day at about 60-70mph. You will be able to stop for a short while at any point.

3. Passports: Doesn't sound great for paranoid Iranian police who are convinced everyone is a spy. I would try to use only one passport and keep the other one out of sight as a backup.

But again, this was Nov/Dec 2009.

Have fun!

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2011-2012: 5 months in Chile
2009-2010: 5 months in Turkey-Iran-Pakistan-India