runs great,other than 3/4 throttle

[hondamaniac]

ok, so i have an 85 250 sx.. she runs pretty strong for the most part... i have noticed a bog at idle when cold an a bog at 3/4 throttle.. warm or cold.... also when it bogs at 3/4 an up it almost stutters then clears up... well after reading some threads on here an understanding what needle does what i think i have it under control.. but i do have a few questions before i just go out there an turn some screws..

im thinking the main is off, but not by much, i could be wrong but from what i have read 3/4 issues are main needle issues...
also... what kind of movement is best to turn the screw... say a sixteenth of a turn? or an eighth of a turn at a time? then drive an see etc...
this is my first rodeo with an actual adjustment on this machine .. just looking for some pointers...

thanks for all the help/ suggestions in advance
nate :TrikesOwn

[briano]

The needle and the main jet are inside the carb, to adjust the jet you need to change it, and to adjust the needle there is a clip on the top of the needle that you can move into a different groove. Move the clip up which would lower the needle will make it leaner, move the clip down which moves the needle up makes it richer. I'd try just cleaning the carb and not change anything first. Take the carb off, remove the bowl from the bottom, romove the two jets and the floats, spray everything out with carb cleaner and leave it sit for a minute then spray it out again. Make sure you spray the cleaner through the jets and it goes through, then used compressed air to blow out passages. The air screw on the side, turn it in slowly counting how many turns till it stops DON'T FORCE IT, then take it out and spray carb cleaner through the passage there, also clean the end of that screw. Put everything back together and make sure the mixture screw is turned out the number that you counted.

[MonroeMike]

http://www.3wheelerworld.com/showthread.php?55086-Carb-Jetting-101-Terms-Tips-and-Jetting-Theory