"The Lawn Mower Repair Man's Front Page"
11/18/00LMRM; Bob :<=
This little tip won't be new to anyone who's been repairing small engine carbs a while but just may save the day for the DIY'er making his/her first effort.
When replacing the float needle seat, there is a right and wrong way to put the seat in. It's really difficult to see any difference with the naked eye but a close inspection with a magnifying glass or enlarged picture will make it clear. Below are two shots of the same seat, one from each side.
Notice the picture on the left, the hole has a rounded edge. This is so the needle will easily center itself and seal. On the right, the hole is sharp edged and not particularly even. The needle will not seal well if this side of the seat is toward the needle. You'll also notice the picture on the right has a well defined groove around the seat body. This is to make identifying which side is which possible without getting out a magnifying glass. The grooved side enters the carb body first. If you can see the groove when the seat is installed, you've done it wrong.
Actually this tip also applies to many newer Briggs engines as well as a few older Briggs. It's been a common feature with Tecumsehs for as long as I can remember.
Another tip that is just for Tecumseh is how the needle is hung from the float. The picture I took for this didn't come out clear and when I get one it will be added here as well. The wire clip that connects the float needle to the float is what is of concern here. The open end of the wire that hangs from the float must aim towards the air intake or air filter side of the carb. If it's pointing toward the engine side, the needle won't center correctly and may leak. This makes absolutely no sense to me but it's an advisory from Tecumseh I picked up on years ago. Once I started following their advise, the vast majority of un-explained flooding carbs (after being rebuilt) mysteriously ended. So although the reason isn't readily apparent, it does work.
One last tip on Tecumseh carbs, this one is for the diaphragm carb mostly found on many older engines but it's still around on a few newer models. There are two versions, both look the same. This makes for some confusion as installation of the diaphragm and diaphragm gasket are reversed on the two. On most, the diaphragm gasket goes against the carb body with the diaphragm next to the outer plate. On the second series, the installation is reversed. This series has a capital "F" cast into the edge of the carb which forms the diaphragm mounting surface.
If the "F" series has the installation wrong, it will run lean, very lean. If the standard series is installed wrong, the carb will likely flood while running or while setting turned off.