Mbc Spray Gun, 704E

No. Immerse only the front end, until the solvent just covers the fluid connection. Submerging the whole gun dissolves the lubricant in the packings (the gun starts spitting and the packings dry out), washes the lube off the wear surfaces, and lets residue from dirty solvent clog the narrow air passages.

The right routine: brush accumulated paint off with a bristle brush and solvent, flush the fluid passages, wipe the body with a solvent-dampened rag, then lubricate the needle packing, air valve packing, side-port packing and trigger pivot. Never clean nozzle holes with anything harder than brass; soak them in solvent and blow them out.

Two causes, both about balance rather than dirt:

1. Atomizing air pressure too high. Reduce it at the regulator.
2. Trying to get too wide a fan with thin material (fluid starved). Open the material control fully by turning it to the left, and at the same time turn the spray-width (side-port) control to the right. The fan gets narrower but the split disappears.

On pressure feed, raising fluid pressure has the same effect. The opposite fault, a heavy center, means too much fluid for the air: reduce fluid flow or thin the material.

Set it by measured flow, not by feel. With atomizing air shut off and the air cap removed, pull the trigger into a graduated container for 10 seconds and multiply by 6. That is your fluid flow in ounces per minute. For standard finishing, Binks targets 14 to 16 oz/min; if you are below that, raise container pressure and repeat.

Starting points: about 6 PSI for a remote 2-quart cup and about 15 PSI for a 2-gallon or larger tank, with the gun's fluid screw open to the first thread. Then refit the cap, set atomizing air at roughly 30 PSI and tune until particle size is even across the pattern.

Spitting means air is getting into the fluid stream. Three causes cover almost every case:

1. Dry fluid needle packing. Back off the knurled packing nut, put two drops of machine oil on the packing, replace the nut finger-tight. If it keeps spitting, replace the packing.
2. Dirt between the fluid nozzle and its seat, or a loose nozzle. Remove the nozzle, wipe the back of it and the seat with a thinner-wet rag, refit and draw it up tight.
3. A loose or defective swivel nut on the siphon cup or fluid hose. Tighten or replace.

Daily, and after every pass through a gun washer:

• Fluid needle packing (where the needle enters the packing nut)
• Air valve packing or air valve stem
• Trigger bearing screw or stud
• Side-port / fan adjusting valve packing and adjusting-screw threads
• Air cap and baffle threads: clean, then two drops of lube before fitting the retaining ring

Use a light machine oil or Binks SSL-10 spray gun lube, which contains no silicone or petroleum distillates that could contaminate paint. Coat the fluid needle spring and air valve spring with a light film of petroleum jelly, keeping it out of the air passages.

20–25 ft-lb, with a drop of lube on the threads first. Do not overtighten; it distorts the seat. More important than the number is protecting the needle while you do it: either pull and hold the trigger while tightening or loosening the tip, or remove the fluid needle adjusting screw so the spring is not pressing the needle collar into the tip. Skip that and you bend the needle or score the tip.

The same rule applies to the JGA-510 fluid inlet adapter (20–25 ft-lb with blue 242 Loctite and the locknut tightened) and the JGA baffle fluid tip at 12–15 ft-lb. On an MBC, if the needle still binds after reassembly the spray head is misaligned: tap around its perimeter with a wooden mallet and retighten the lock bolt.

KK-4058-1 is the repair kit for the Binks MBC-510 family (30EX, 64HDD, 704E). It contains a quantity of the soft parts needed for a complete gun repair: the sprayhead gasket, needle packing, air valve U-cup, washer and snap ring, air valve gaskets, fan-valve packing and cylinder gasket, so you can rebuild the gun on the bench without ordering ten separate kits. Binks recommends keeping one on hand.

What it does not include is the fluid tip and needle, which are chosen by size and replaced as a matched pair, or the air cap. Related MBC parts: MBC-1225 baffle, MBC-415 cylinder assembly, P-MBC-402 spray head body and the JGS-449-1 air valve assembly. JGA-510 guns use the KK-4987-2 kit instead.

Spray a test pattern, rotate the air cap one-half turn, and spray again.

• Defect flips to the other side: the obstruction is on the air cap. Soak it in solvent and clear the horn holes with a toothpick or broom straw. Never use wire; it enlarges the hole and the cap is scrap.
• Defect stays put: the problem is on the fluid tip. Look for dried paint just inside the opening (wash with solvent) or a fine burr on the edge (remove with #600 wet-or-dry paper).

A loose air cap gives the same lopsided pattern, so tighten the retaining ring first. If cleaning does not fix it, replace the cap: stocked caps include the Binks 66SD and 66SK for the 2100 and the 64HD, 62HD and 704 for JGA and MBC guns.