I have just bought this and its got a list of illnesses , the main and really only one left,  is a worn carb. I would like to replace the original TK for the equivlent Mikuni. After making some enquires it appears the dark arts of carburation are in force when it comes to this particular Yamaha. Would any kind person help me in pointing at the carb I might need, along with the relevent jet / needle sizes so I at least try and get it to run halfway right. I would love it to be a bolt on straight of the box , is this really too much to ask..

 

Thanks in advance

Yamaha seems to have had there own model of carb made by mikuni at the time, the model that was used on the next models was called vm26ss. I think a off the shelf 26mm should fit just change the jets to match what is listed as standard below, personally I'd only change pilot & main jets to start with & go from there as often the slide, needle & needle jet are close enough

 

http://www.cmsnl.com/yamaha-ty250c-1976_model8576/partslist/%21SERVIC1.html#results

 

There are a few places online that list readily set up carbs for TYs, sometimes they are listed on eBay