Rejetting or just needle ajustment?

[Frankencelery]

Last summer I put a new carb on my ATC90. The boot between the airbox and carb was cracked, so I put on an aftermarket air filter, a dry one that just hangs off the back of the carb. I noticed a fairly significant power increase at the top end. However, it's now unmanageable in cold weather. It has to be choked just so, and the choke has to be adjusted in very slight increments to keep it running as it warms up. Then, if the temp is under 40 degrees, it always has trouble at the bottom end. You have to feather the throttle to get it up and going. So my question is, would moving the needle up (moving the clip down) help with this, or is this something only a larger pilot jet will fix?

[torker]

The needle will help if you do it right. It sounds to me you're lean. Does it bogs when you stab the throttle at low rpms? if it does try raising the needle (moving the clip down) this will give you a bit more fuel from 1/4 up to 1/2 throttle opening. Also try closing the air needle 1/4 turn at a time. It should get better. If only sligthly better you may need a larger jet. Remember that the colder it is, the more fuel the engine will need due to the denser air. If it gets worse go the oposite way.
Hope this helps.
TORKER.

[Dirtcrasher]

When the weather change is that drastic, and your running an "open" filter. You most likely need jetting across the board. Starter, air screw, needle and main jet.

If you hadn't changed that main jet before with that open filter, I'll bet you were missing out on some great gains.

Read the sticky about jetting, and make one change at a time. The best situation is to have 2 carbs, one jetted for warm weather and another for cold.

Were not Ricky Charmichael so we won't be jetting at every single different altitude, although, if you end up high in the mountains - you'll feel the change!!