One advice if you are planning on bringing your bike to Sri Lanka forget it!
the taxes are damn high.
go for the first option.

I went to Sri Lanka with my cousin and learned some good lessons. :nono:

It will all depend on what kind of bike you have and how long you want to stay. If your bike has over 350cc in engine capacity, you could face a lot of problems to get it into the country. You will need a special clearance from the Defence Ministry. Usually, as a tourist, and for temporary import, it could be done, but the red tape could be lengthy as well. As you would only temporarily import the bike, and re-export again, no import duties are to be paid.
If you want to stay just a short while, your biggest disadvantage would be transport cost. Sri Lanka is (still) an island, so you'll have to ship it in and ship it out again. So it might be wiser to send to bike to wherever you would start your 'continental' part of the Asian trip, and rent a bike while you're in Sri Lanka.
The other guys gave you good advice: head straight to Negombo if you want to rent a bike. It's close to the airport and has much more rental facilities (as a tourist spot) than Colombo. About 25 km around Colombo, traffic is hell also. I know, I'm travelling from Negombo to Colombo every day!
If you need more advice, or any help, just ask, and I'll see what I can do.

For cars, certainly, up to 300% on a combination list of duties. But not so on bikes. Indian bikes are about 10% more expensive in Sri Lanka than in India. Japanese bike prices are in line with the international rule-of-thumb : $1000-1200 for every 100cc, so it can't be that import duties on bikes are so high.
Limitations are however there: less than 350cc and less than 4 years old. But this last one - I believe - only counts for permanent import, not for temporary import (the bike leaving with you again).

Well, after the good mention of Suranga in this thread (his site: ....:::: Contact Us ::::....), I thought I would give him a try. It didn't work out well, so I thought I would warn others.

I e-mailed him to reserve a bike a few weeks ago, he confirmed the reservation. Today he's come back and said that he's had an "unexpected booking" for all of his bikes, and that the bike he had reserved for me is now, well, being given to someone else.

In the meantime I had planned my vacation around picking up a bike with him, so it is rather inconvenient, to say the least, that he has cancelled my reservation. I have cancelled all of my arrangements with him (moto, room, airport pickup) and let him know that I will do business with people that know how to keep their word. I urge everyone to do the same.