Had to look up what a Boardtracker is. Interesting project. I assume you are in the planning stages and further assume the lack of response is because you have not specified which 125 engine you want specs for (Virago or Star?). Most of the pics of 1900 Boardtrackers I saw were single cylinder engines… are you sure you want a Vtwin for this project?. Furthermore the weight of the engine is not something normally specified in the technical specifications and I guess this would depend on what parts of the engine are included or not when it is weighed. These Yamaha 125’s Vtwins are also not easy to get hold of as far as I know. Easier to get a 535 for less although the problem would be the shaft drive.