A couple of months ago I did some work for a motor cycle business in Canada, for his ebay store. I also buy items on ebay, and most of those are located down in the States.
The little I've learned is this: (this won't matter to you in this case, but it might be where you heard it). US to Canada has a better chance of avoiding Canada Customs if the item is shipped USPS rather than UPS. I don't know why that is, but it is...
During the short time I worked at the shop, it seemed that for Canada to the US, UPS was the best way to ship. It is a little more expensive than comparable service from Canada Post, but somehow it seems to cross the border easier, and it's usually a little easier for the person doing the shipping.
As far as US Customs is concerned, I believe a declared contents value of (US) $200.00 or more will trigger your Customs people, and you may be charged duty. That's pretty easy to check at
http://www.cbp.gov/xp/cgov/import/duty_rates/If your vendor is close to the border and a US Post Office, then taking the pipes across personally, and shipping them from the US to you, is actually a good idea. (If it’s practical, of course.) Regardless of where you ship from, if you're required to list contents use "used" not "vintage" to describe the motorcycle parts.
The place I worked ebay store is
http://stores.ebay.ca/MOTORBIKE-TORONTO_W0QQssPageNameZstrkQ3amefsQ3amesstQQtZkmThe owner loads up his site with quite of bit of shipping info, and you might find some useful info there.
Finally, you may want to get the dimensions and weight of your item(s), the Canuck postal code of your vendor, and go to
http://www.ups.com/content/ca/en/index.jsx and figure it out.
Good luck with it ...