Imperial Fuel Valves

There are better, more modern valves than the old Imperials, but the new valves are expensive and they're not ORIGINAL so let's take a few minutes to fix up our old fuel valves.  There are three major problems with the Imperial valves: (1) they can "sieze" or lock up so you cannot turn the fuel on OR off  (2) they can leak in the Off position so that fuel runs through when you don't want it, resulting in a dripping carb or overflowing main tank and (3) most annoying of all is a leak around the stem which results in fuel dripping INSIDE the cockpit!

It doesn't take long to spruce up this old girls...take them apart by removing the handle and unscrewing the top, pull out the stem and spring.  There's a half round washer that will tip up when you pull on the stem.  It has a tab on the back side so you have to pull the tab out of its notch to get the washer free.  Clean everything using a toothbrush and MEK

Next you'll "lap" the stem into the tapered body of the valve.  There are special lapping compounds available, but most folks use toothpaste (a nice smelling mild abrasive).  Coat the stem with toothpaste (Photo 2) and then put it back into the valve body.  Use the handle to turn the stem back and forth in the body as if you're turning the valve on and off.  Do that a hundred times or more and the toothpaste will start to wear the stem and body so that they match perfectly.  Remove the stem and you can tell the lapping is working because the toothpaste has turned black.  Wash off the toothpaste to check lapping progress.  You're done lapping when the stem and body look nice and shiney.  Photo 3 shows a comparison of before and after lapping the stem.

Finally, re-assemble the valve using a new seal and fuel lube grease.  Newer (!?) Imperial valves use O-ring seals, just put a new one on.  But the older valves used leather seals which are no longer available.  I haven't tried this but people tell me you can use waxed dental floss or teflon string wrapped around the stem to replace the leather seals.

Engine primer

Not much to overhauling the engine primer, but you'll need to have on hand two O-rings of the correct size (Kohler takes a -12 O-ring) and a very small amount of fuel lube grease (EZ Turn).

First, unscrew the locknut and pull the plunger out of the barrell (Photo 1).  Remove the old O-rings from the plunger...they may just fall off if they're more than 15 years old.  Examine the inside of the barrell for any dirt, crud, or scratches.

Apply a light coat of special grease to the new O-rings and to the end of the plunger (Photo 2)  Roll one O-ring into the first groove, the roll the second O-ring over the first and into the second groove.

Finally, grease the plunger and barrell good and reassemble.  (Photo 4) Test the unit.  If there's any problems, remove the check valve springs and balls (under the two screw covers on the end of the primer) and clean and lube them.

Fuel system test rig

Easy to make (and cheap) test rig for fuel systems.  Use it to test valves, fuel line connections, gascolator, carburetor float level, etc.  Consists of:

(Photo 1)  1 1/4 to 3/4 reducer coupling...makes the reservoir for the test fuel.  Wrap a piece of safety wire around it so you can hang it up.  Needs at least 19 inch "head" above the item being leak tested.

3/4 to 3/8 bushing to step down to the hose barb

3/8 pipe to 3/8 hose barb

4 feet or so of 3/8 inside diameter vinyl hose

(Photo 2), two more 3/8 pipe to 3/8 hose barbs

3/8 ball type valve, and

another 2 feet or so of that 3/8 ID hose

and a few hose clamps, total cost about $10

To use your tester hang it at least 19" above your work bench and attach the loose end to the valve or whatever you're testing.  Fill the reservoir with fuel or even with water (I use E85 because of its low density and distinctive fruity smell).  Open the hosevalve and wait...if no leaks appear, wait overnight then give it the smell test (if using water place a piece of paper under your test item and see if its damp in the morning).  Of course if you use fuel to test your fuel system components, you should test outdoors and away from any ignition source!