There's another option if you don't want to change air cleaner and rejet. If you leave the intake stock, you can adjust the air/fuel mixture only and this can be done whether you open up the exhaust or not. Altering the exhaust only and leaving the intake stock shouldn't require a rejet. <br />
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These machines are notoriously set too lean from the factory. On the side of the carb, you should see a small round brass plug (it might have a tiny hole in the middle of the plug). Use a metal screw and thread it into the plug only a slight bit then pull that plug out. This allows you access to the air/fuel mixture screw. Turn the a/f mixture screw in clockwise until l-i-g-h-t-l-y seated, then back it out 2 full turns. Fire up the trike and let it warm up fully (carb adjustments should be done with a fully warmed up engine) Once warmed up, lower the idle slightly. From 2 full turns out on the a/f mixture screw, turn it in slowly until it just starts to stumble, counting the number of turns going in.
Then back it out again, counting the number of turns going out until it starts to stumble again, then turn it back in 1/2 way splitting the difference between counted turns in & out. This should bring you to the sweet spot and enhance the general performance now that it's getting the proper amount of fuel and no longer running too lean. Last step is to adjust your idle back to the normal idle rpm spec and you're done <img src="images/smilies/thumbup.gif" border="0" alt="" title="ThumbUp" class="inlineimg" />