1 - Cheap solution for touring# if the motive is only to gain good power for making bike make good climbs with load or pillion riding (double swari) on tours and you dont want bike to get an engine over haul at every tour end then opt for a 110cc united engine which is being used in its "chand gari" rickshaw..

2 - little expensive solition but really long life more power# Even bettr would be if you opt all aluminium block sports or a pit bike 110cc varaint of same engine that comes in scrap yards thats bit expensive and would cost around 15~16k in neat clean condition.

3 - If you plan to use it for racing then opt for a 150cc ~ 180cc which will pull the C70 to speeds not safe for ride or the rider.. hence braking, wheels, tirs all would require a major upgrade.
