QUESTION: I can't get any purge air.
ANSWER: Here is a link to a cutaway view of the internal ports in the handle: http://www.spfdepot.com/handles_p/spf-gun%20handl... the wet end, rear cap and piston so all you have is a handle.
Attach your air hose to the gun handle and turn the ball valve on to allow air to flow. When you pull the trigger, air should come in from the 1/8" hole closest to the rear of the gun. This causes the piston to move forward. When you release the trigger, air should flow from the other hole just in front of the one on the rear. This causes the piston to retract.
AT ALL TIMES, air should be flowing from the small hole in the front of the gun where the piston comes out and you put the chamber on. This is the purge supply air port.If you don't have any purge air, then you either have the handle port plugged and/or the internal port on the valve spool is plugged or both.
The internal port on the valve spool (the thingy the trigger moves that has the 3 small o-rings on it - otherwise referred to as a valve spool, or assembly #32) is hollow and allows air to flow to the piston sides and the purge air to the front of the gun.
To see were the problem is check the internal port of the #32 valve spool first. Next remove the muffler and the pipe plug from the bottom of the handle. Remove the air fitting plug and valve spool. We have a drill bit we offer that is 1/8" x 10" .
BY HAND - Run this bit from the bottom, work it through the valve spool house and up till it stops. Twist the bit by hand to clean out ports as you go. You will know when you hit metal. Do this through both ports on the bottom of the handle. NOW come to the small ports inside the handle. They are angled at a 45 angle and goes about an inch. Again, you will hit metal. Do this to all the small ports inside the gun.
To thoroughly clean the internal ports, soak for an hour in SPF-6, then in the SPF- ISO Solvent. Rinse with Zylene to remove all remains of the solvents.
DO NOT DRILL through the valve spool housing section - work it through by hand and you can then trigger a drill to clean it. Drilling through the valve section can ruin the valve seat in the handle.