If you do work outside of Canada on the motor vehicle and let them know in the border they can ding you for the full GST of the repair or even on the whole value of the bike.
http://www.aacb.com/resources/travel1.asp
Repairs or modifications to your vehicle
If you intend to have repairs or modifications made to your vehicle outside Canada, check with us before you leave. Under customs law, we can no longer consider your vehicle, vessel, or aircraft to be Canadian if you increase its value, improve its condition, or modify it while abroad. As a result, you may have to pay duty on its entire value when you bring it back.
Repairs or alterations to vehicles, aircraft, or vessels carried out in the United States, Mexico, Chile, or Israel will be free of customs duty when the vehicles are exported to these countries for the declared purpose of repair or alteration. The goods and services tax (GST) or harmonized sales tax (HST) will apply to the value of the repair or alteration.
You can have incidental minor repairs made or parts replaced while you are travelling abroad to maintain your vehicle in an operating condition. Although these minor modifications do not make the whole vehicle subject to assessment, you may still have to pay duties on the repairs and parts.
