Not sure what the stock jet size is. Compression was 8.6 to 1 compared to 9.2 to 1 for the standard 750. Go up on the mains at least one size maybe two and try the standard pilot jet but adjust the idle screws and see if you can get it adjusted. You may need to raise the needle also but really you need to just see how it runs and adjust from there, there is no set jet size for anything you change because so many things affect jetting......altitude, temperature, general engine condition, how good your tune-up is, amount of restriction in the air filter and amount of restriction in the exhaust. Different designs of 4 into 1 will require different jetting depending on how efficient the design is, some scavange very well and some designs are just plane lumps of metal.