Jetting carbs?

[Dirtcrasher]

When you guys make mods how do you know which jets to buy? If it's not recommended how are you supposed to know? If you want richer or leaner do you just buy the next to in order jumps each way? Or do they sell a tuning kit with 6 mains and pilots and needles in it? Not only relating to my SX hope 350X carb but the pipe I will put on my Blaster. Suppose I try the next higher main and it is to lean, do I just eat them and try try again?? Do they go in sizes 138, 139,140 etc. or is each manufacturer different?? Thanks! :?

[ATCnut]

For my 350x the stock main jet is a 138. The sizes go 130, 132, 135, 138, 149, 142, 145, .... I run a 140 at the Oregon dunes (Sea Level), the 138 here at home (~500 ft), a 135 at my inlaws mountian cabin (2500-4000 ft), and a 132 at St Anthony's (5000 - 6000 ft). Main Jets are about $4 apiece, so I have a bunch of different sizes. I end up loaning them to people at different riding spots. It does not cost a lot to have all the jets you need to tune your trike

[Dirtcrasher]

Does anywhere sell a tuning kit?

[TimSr]

First thing is to do the mod you are considering, and see if it actually needs carburetion changes. About half the time you change apipe iot wont even need it, and if it does, usually about one jet size in the right direction will do it, and you base it on plug readings. There is no formula for this pipe=this jet, etc.
DK sells kits which are 5 jets for about $20.00.
Its very unlikely that any mod other than a big bore kit (not an overbore) will require a pilot jet change, and its very unlikely you will need a different needle, or even a clip height change if its okay now, since a main will change midrange proportionally to the top.
In other words, your probably making this WAY too complicated. Change your pipe, ride it for a while , and monitor your plug. If its off, change a main jet size in the direction you need to go.