Garmin Zumo 550..... down hill from there. You can save money on others but in the long run it is the best suited for motorcycles and adding bike to bike, music, cell phone and XM.
I have owned Garmin units for 10years and use their software on my computer to plan routes and download POI files from the internet.
$85 is hard to debate, you will need to know many things before you pull the trigger.
1. What are the mounting issues.
2. Power supply hook up.
3. Does it have audio turn by turn? Can you hear it in your helmet? Looking down at the GPS while riding is a bad idea.
4. Can you make routes before/prior to a planned trip?
5. Are map and software upgrades available?
6. Can it handle outside environment? Rain, sun, dust, and most of all vibration.
7. Tech support, if you know someone with the same model and knows the function it is very handy to call and get info on the operation.
Just a couple of things to consider.
A lot can be said for getting what others use and have done all the real world testing.
You will find the Zumo 550 is hard to beat despite the cost. Check other forums, BMW, ST1300, Goldwing etc, the people logging big miles are the ones to ask.
On the surface it looks like a great deal, it may be an $85 gamble and work out fine. Or it may be an $85 pet rock.