Briggs 28n707

[Rick O]

Does the compression release ever break or malfunction where it is always engaged so as to affect the low speed and need full choke to run at full speed?

 

[slomo]

Can it fail, sure.

Needing full choke to run is a dirty carb and or lack of fuel delivery. Possible fuel tank vent failure.

 

[Rick O]

Can it fail, sure.

Needing full choke to run is a dirty carb and or lack of fuel delivery. Possible fuel tank vent failure.

new carb and no dirt or restriction as I replaced all lines from the tank and filter with fuel flowing freely. It appears to hiccup or fart occasionally, but not backfire. Full choke runs the best but runs at a higher RPM, Compression gage read 90 psi in about 4 revolutions.

 

[Auto Doc's]

According to the number, this is a single cylinder push mower engine. Does it have an auto choke function?

Compression release is only to aid in engine cranking at startup so it can spin faster. If it were not working the engine would fight the pull starter while trying to turn.

This sounds more like you possibly have a vacuum leak between the carburetor and the engine intake.

An ignition coil or spark plug failing can do some strange things like this as well.

 

[Rick O]

It is a 38" riding mower. I pulled the head again and lapped the valves today and they were ok as I suspected. I also looked at the flywheel key and I adjusted the gov. I put on another carb which is a little better but it pops and farts intermittently. It must be a worn camshaft.
I was thinking if the compression release broke off but the pin remained in bump position it my do funky crap.

 

[Auto Doc's]

Darn this site, it erased my reply again.

Check the gaskets and make sure one is not upside down and blocking the carburetor vent, it is easy to do.