Here is the question. On the camshaft which includes the timing ear is a little metal spring-loaded clip with legs that straddle one of the camshaft spokes where a hair-spring holds it in position…The position of the clip might be RPM sensitive…Does anyone know the purpose of this clip? Iit does not seem to interface with any other parts, which are minimal. This engine is a basic as it gets…I’m working on a picture…
Try these guys
Could it be part of the centrifugal governor? Does it look like it could move a arm that goes out the side of the block?
No! It’s a compression release! At cranking speed, it holds the exhaust valve open a little…When the engine starts, it moves out of the way…
Yes CAddyman. And if that flap hangs up the engine will not start and the problem might be diagnosed as jumped time or a stuck valve. I assumed that it allowed the rope to crank the engine fast enough to prime the carburetor and trigger the electronic impulse ignition. Tecumseh engines have been notorious for being difficult to start, requiring a great deal of strength to overcome compression and I guessed that Briggs & Stratton wanted to make the best of the situation and as engines grew in displacement they added that gizmo to reduce frustration when starting. Also, their latest recoil starter uses plastic dogs that are quite weak and the decompression tab might reduce warranty comebacks from failed start mechanisms.
I guess I haven’t had a Briggs or Tech opened up in the past 20 years so not familiar with this. In 87 I bought a Toro mower with a Suzuki engine. I told the guy I wanted electric start because I was sick and tired of trying to pull start my old mower. He said I didn’t need it with the Toro because it was guaranteed to start on the first or second pull. It used a compression release to make rope pulling easier-and it worked great. That was the first I came across that feature and then heard the others were doing the same later on.
If I rotated the camshaft 180 degrees, you would see the other end of the clip resting against the exhaust valve cam lobe where it is high enough to just barely hold the tappet up a little, releasing some compression…When the engine starts, centrifugal force pivots the clip out of the way of the tappet and full compression is restored…The clip pivots on that pin through the camshaft…The plastic cam lobes seem to work fine …Valve spring tension is pretty light so no great pressure on them…
Sorry I didn’t look at this earlier. I’m no Briggs and Stratton expert but I remembered that my wife gave me this book years ago. Now I finally get to use it.
The new photobucket seems to have a few bugs but to view this, click on the image, it will take you to the thumbnail at photo bucket. Put your cursor over the picture for a few seconds and a bar will appear at the top, move the cursor to the end where it says zoom and select original size from the drop box. It will be readable then.
How come the include picture doesn’t work any more?