.026 is stock dia. of main jet on my carb to go leaner solder shut and drill smaller my suggestion is one size at a time. Most adjustment can be made with the e-clip on the needle. This mostly affects 1/3 to wide open and very little on the idle. If you can't get it tuned with the e-clip and want to go richer make sure of your stock size then drill the next size bigger then test your bike. I have found some other carbs have 0.025 main jets.