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http://www.smallenginerepairs.info/20110118_briggs-stratton-vacu-jet-pulsa-jet-carburetor.html#comment-51

Briggs & Stratton Vacu-Jet & Pulsa-Jet Carburetor

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Posted by Jake on January 18, 2011

 in Briggs and Stratton

Figure 4-2 illustrates the Vacu-Jet mechanism, which is distinguished by a single pickup tube and tandem discharge ports controlled by flow through a single jet. Figure 4-22 shows the three basic forms of this carburetor.The Pulsa-Jet derives from the Vacu-Jet and in its various permutations uses many of the same parts. The distinction between the two is that the Pulsa-Jet feeds from a reservoir in the top of the fuel tank, which it replenishes with a vacuum-powered fuel pump (Fig. 4-23). Pulsa-Jets have two pickup tubes. The longer one transfers fuel from the tank to the reservoir; the shorter tube draws from the reservoir into the carburetor. This arrangement isolates the carburetor from changes in the level of fuel in the tank. Vacu-Jets lean out as the tank depletes.

Figure 4-24 illustrates major Pulsa-Jet variations that closely track those of the Vacu-Jet. Most service information applies to both types.

Needle-valve assembly Sealing the needle valve, or mixture-adjustment screw, involves some fairly complex engineering. Figure 4-25A shows the arrangement of washers and O-rings generally found on pot-metal Vacu-and Pulsa-Jets. Figure 4-25B illustrates the arrangement always used on nylon carburetors and sometimes on the zinc models. The needle is quite vulnerable to damage from overtightening.

Pickup tubes Vacu-Jet fuel pickup tubes are fitted with a check ball, which tends to stick in the closed position. Because the ball and, on later models, the tube itself are made of nylon, more than a few minutes in carburetor cleaner is all that can be tolerated. As an emergency repair, you can free the ball by gently inserting a fine wire through the screen in the base of the tube. Eventually the assembly will have to be replaced.

Fuel pickup tubes supplied with zinc carburetors twist off and on. Tubes used with nylon carburetors snap in and out, an operation that can require considerable force (Fig. 4-25).

Pulsa-Jet pump diaphragm The side-mounted diaphragm is shown in Fig. 4-26. The tank-mounted version, used with “bobtail” carburetors, is illustrated in Fig. 4-10. In either case, replace the diaphragm whenever the carburetor is serviced.

Someone who knows what he's talking about.

Here's someone who knows of what he speaks:

http://www.smallenginerepairs.info/20110118_briggs-stratton-starters-sprag-clutch.html

Note the stuff highlighted in yellow (the second sentence). Hmmmm. Should have read this. (See my earlier post.)

Briggs & Stratton Starters Sprag clutch

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Posted by Jake on January 18, 2011

 in Briggs and Stratton

Sprag clutch Recoil and impulse starters drive through a sprag clutch that doubles as the flywheel nut. The clutch housing (Fig. 5-12) threads over the crankshaft. The sprag (ratchet in the drawing) is supported by a bushing on the crankshaft stub. Its outside end mates with the starter pulley, and its lower, or inside, end rides against four or six ball bearings in the starter housing. When rotated by the starter pulley, the sprag traps a ball bearing between it and the clutch housing, locking the starter to the crankshaft. Once the engine catches, the ball bearing releases and the sprag idles on the bushing.

To service the clutch, remove the engine shroud and the screen, which is mounted to the clutch housing by four self-threading screws. Disconnect and ground the spark-plug lead to prevent accidental starting. Secure the flywheel with a strap wrench or a Briggs & Stratton holding fixture. Unthread the clutch assembly using factory tool PN 19161 or 19114. If this tool is not available, the assembly can be loosened with a hammer and a block of soft wood. Some damage to the screen lugs is inevitable but is less than fatal if distributed evenly to all four lugs. A spring washer fits under the clutch assembly.

On early models, the retainer cover was secured with a spring wire; on late models, the cover must be pried off. Clean the sprag, clutch housing, and ball bearings in solvent. Some deformation of the clutch housing is normal. Wear on the tip of the sprag, the part that makes contact with the bearings, can cause the clutch to slip. Reassemble these parts dry, without lubricant, and lightly oil the bushing. Install the spring washer and torque to specifications in Table 5-1.

One born every minute

I bought an old Craftsman snowblower for $50. It worked very nicely for a while, before the snow arrived. Then we had freezing rain and snow. It didn't work well after. I tried changing the spark, but that didn't work. The compression is not bad, over 70 psi. at least. Carb seemed to be working nicely, and the spark smell like gas after I try to start it. Just in case, I sprayed carb cleaner into the cylinder, replaced the spark, and cranked. No start.

I used a spark tester (Princess Auto). No spark when connected to the spark plug. But I did get a spark in the tester when I grounded it to certain fins on the cylinder head. (Only certain fins, not all, not when I touched it to the top of the spark.)

I think there must be something wrong with the magneto, or with the line from the magneto to the spark. Sooo, today's project was to strip off the housing and get at the magneto. EasiePeasie.

But, this engine has a condenser and points. And these are located behind the flywheel. So, I tried to remove the flywheel. The only problem was that the starter housing is located in front of the flywheel. So I tried to remove the flywheel. One born every minute.

I spent at least an hour with a gear puller, trying to get it lined up behind the housing. Pretty stubborn. So I call over my friend Brian. He brought some crowbars. We tried crowbarring the housing off. No way.

Brian had to go shopping, so I stayed. Took a propane torch and heated up the housing to sweat it off the crankcase. Then reapplied the gear puller and tightened it hard. Woopeee! I could feel something moving....

As it turns out, the housing is affixed to a nut. I managed to pull the housing off the nut (breaking it.....).

So here's the nut with the remnants of the housing around it, kind of broken up. In fact it was very easy to release the nut with a wrench. Didn't take much energy.... If only I'd known to do that before breaking the housing.

Here's the housing part that broke away.

Here's a dish with the front of the housing, a washer, and iron balls. The front of the housing is connected to a square shaped fixture that fits over the end of the crankshaft.

Here's the nut that screwed onto the crankshaft. You can see it is attached to the back of the housing.

The flywheel was easy to take off. And here's where you get. The indication on the condenser points cover, which says: "Don't use a steel key." That makes sense, since an aluminum key would shear, but not necessarily a steel key.

Take the cover off, and there's the condenser and point.

Sorry, a little fuzzy.

There, that's slightly better.

There are two wires leading to the condenser. One goes to the spark. The other, I presume, goes to the power switch -- off, on, with a key -- or grounds out. There is a little hole in the end of the rod leading out of the condenser. You fit the ends of both wires in the hole. The spring (which you've already threaded on the rod) expands and hold the wires in place.

Magneto and condenser. Two wires.

Two wires.

Two more shots of the condenser.

Triole has a new magneto for $60. I didn't ask them about the condenser. I'll see if I can figure out how to test the condenser and the line from the magneto to the spark.

I also have another engine, very similar to this one. (Takes a different spark, and looks to be much older.) It has great compression, but I need to work on its carb. If I get it working, I might switch it for the one above. (It seems to have the same starter housing, so no excuses for destroying it.)