Okay, here's one of my favorites.
Take the Mercier bridge off highway 20 towards Chateauguay and stay on the 138 all the way to Huntington. When you get to Huntington, turn left over the bridge (only one) hang a right at the next stop and head towards Athelstan/Hinckenbrook and keep the river at your right. You'll be looking for signs heading your towards Franklin/Hemmingford which will eventually have you ending up in Lacolle.
This is one of the prettiest roads in Qc. with hills and twisties to boot! There's ways you can get "lost" on it, but seeing that it sides the US border, you'll always end up back on the main route. If you're going to play with the bike while you're there, you need not worry too much about law enforcment, but do keep a weary eye for the occasional deer at sundown or the sight seeing tourist slowing down.
When you do get to Lacolle, skip getting on the 15 back to Montreal and overshoot the 15 until the next left. That'll give you another sweet back road all the way to Napierville where (on weekends) you can get yourself some refreshment and enjoy some fairly decent drag racing at the local strip.