Part 2 of my earlier message: BTW, it really helps to have the parts diagram nearby.
Short-term Solution:
This should solve the symptoms of your problem.
How-to Clean and Lube a High Performance Valve Piston
by Adam Rice
Refer to the appropriate parts guide, which can be found at
http://www.iwata-airbrush.com/support/specs.jsp
Equipment
* Towel or Tray to work over
* Needle Nose Pliers or Tweezers
* Cotton Swabs
* Cleaning Solvent
o Laquer Thinner
o Acetone
o Alcohol
Disassembly
1. Unscrew the Handle
2. Unscrew the Needle Chucking Nut
3. Pull out the Needle
4. Unscrew the Spring Guide
5. Remove the Needle Spring
6. Remove the Needle Chucking Guide
7. Pull the Main Lever up and out
8. Turn the Airbrush Body over your hand and jiggle out the Auxilliary Lever
9. Use the Needle Nose Pliers to pull out the Air Valve Piston
Cleaning and Lubing
1. Use a Cotton Swab to clean off the Valve Piston
2. Remove some of the cotton fibers from a Cotton Swab and clean the hole at the bottom of the Trigger Housing
* Clean until a Cotton Swab comes back clean
3. Place a very small drop of Super Lube on the shaft of the Valve Piston
4. Place the Valve Piston back into the hole at the bottom of the Trigger Housing
5. Place the Main Lever back into the Trigger Housing
Testing
- 1. Press up and down on the Main Lever a few times, it should feel nice and smooth and spring back up when depressed
Reassembly
1. Place the Auxilliary Lever back into the Trigger Housing behind the Main Lever
1. Check the Parts Guide for the proper orientation of the Auxilliary Lever
2. Grab the small tab on the Auxilliary Lever from the side
3. Insert the Auxilliary Lever sideways into the Trigger Housing
4. Twist the Auxilliary Lever into the proper orientation
5. Hint: You ight want to hold the Airbrush Body with the front dipped down slightly to let gravity help instead of fight your efforts
2. Place the Needle Chucking Guide into the Airbrush Body
3. Place the Needle Spring over the Needle Chucking Guide
4. Screw the Spring Guide into the Airbrush Body
5. Push down on the Main Lever at least once
6. Carefully insert the Needle * Warning: This is the most probable time to bend the Needle point
7. Screw the Needle Chucking Nut onto the Needle Chucking Guide
8. Screw the Handle back into the Airbrush Body
Let me know if you run into any problems. I'll be more than happy to help you out.