First off. you don't need a larger carb outright. You can drill that one out to make it larger. Secondly, Search puch seat mod on here. I am not posative, but I think it will work for this bike same as the maxi.
If I get mine running right today I am going to head to Bob's after he gets home from work. You should do the same.
And you should do some plug chops to see if you are running lean or rich. That could help your idle issue. How does it idle with the idle screw turned in more?.