Some of you might be confused as to why I have tips on repairing an engine. Before I became a graphic designer, I repaired lawn mowers for a living, and still do on the side as a hobby. So.. for those of you who are interested in learning how to repair Tecumseh carburators, here goes nothin'
I made a post about this because Tecumseh engines all use the same somewhat inferior Carb design. The flaw is mostly user initiated. Unlike Briggs and Stratton engines which use a painfully simple diaphram for a carb, with no bowl and very few moving parts, Tecumseh engines use a delicate, more elaborate carb with a bowl and worst of all, a carb body with a permanently sealed check valve( ball bearing) that tends to get stuck. These carbs pose an almost reliable list of specific problem areas. Luckily, most can be fixed if you're patient and willing to spend about an hour or so repairing them.
The most common problem these carbs have is a tendency for the bowl to eventually be filled with gum deposits from old gas which sits in it all winter long. These deposits will clog the gas inlet located in the large brass bolt that holds the bowl onto the carb. You can see it pictured in the diagram. Notice that there is a small pinhole on the side. This almost always gets clogged up, and when it does, the engine will not start. You can perform this fix with the carb on the engine as long as you make sure to either drain the gas or make sure the gas line is pulled from the gas tank. I usually remove the tank entirely since they usally just clip on the side of the engine blower housing.
Another common problem is the butterfly valve will sometimes get stuck due to gum deposits as well. Manually twist the butterfly valve( located on top of the carb as seen in the picture with the spring) and make sure it moves easily. If not, then you're probably going to be better off removing the carb.
Most Tecumsehs have the carb held in place with 2 screws near the exhaust. Some of the newer ones are located so close to the muffler that you will have to remove the muffler too. Before you do this, drain the gas or remove the gas tank. Then CAREFULLY pull the carb off of the engine while making a mental note of how the linkage attached to the engine. Be careful NOT to stretch the governor spring. If you do, the engine will run erratically.
Once you have the carb off of the engine, find a clean place to work where you can take it apart and inspect all the parts. Remove the bowl and notice the brass float as pictured above. There is a little pin that holds it into place. Slide that out and gently lift the float out. The needle valve will come out at the same time, which is hung loosely from the float. Next remove the elbow piece that goes from the intake to the side of the carb body. Now that you have it all apart, do a number of simple tests. Gently shake the float. if you hear fluid sloshing around, then it has a leak. These floats are like 4 bucks, so get another one. I've also found that if you can spot the hole, you can solder it and it will work just fine. Next, clean the entire carb body with carb spray. I'd suggest wearing gloves because the spray is nasty stuff. Just watch it eat your gloves to see what I mean. With the body clean, hold the butterfly valve with a finger so it doesn't move and shake it. if you hear what sounds like a ball bearing rattling inside, then you're in good shape. if not, then that's a problem. One of the biggest problems people have with these mowers is that they will accelerate out of control. I've seen many tecumsehs that simply blew up. This is caused by a stuck check valve allowing too much fuel to be thrown into the engine. So you can do one of 2 things: Either get a new carb, or soak the old one for a few days in parts cleaner. You'll have to remove the rubber primer bulb, but I seem to almost always ruin them getting the things out, so while you're at it, order a bew primer bulb. The cleaner will eat anything made out of rubber or plastic, so make sure and remove the gaskets, rubber,etc.
So now that you've got it all cleaned out, put it all back together and see if she'll run. Sometimes they'll start on the first pull, and sometimes it takes all day to get it to run right. This last point being made brings up my last point, which is that if you have a choice between a briggs powered mower and one with a Tecumseh... go with the Briggs for god's sake or else you'll have to do all the stuff I mentioned above. I also wanted to mentioned that I borrowed a few pics of carbs from a few web sites, so thanks in advance. I meant to take my own but the batteries in my camera died, and I'm too lazy on Sundays to run to the store.
