I am stumped. I am working with a 17HP OHV single Briggs, model 311707.
It will start up and idle fine but if I try to rev it up it will misfire and then pop out of the exhaust if I get off the throttle. Sometimes it will eventually come out of the misfire but it still feels like its not very powerful in the higher portion of the RPM band. (See video below)
Here are some things I have already tried to fix the issue:
-Fresh 93 octane
-New spark plug
-Checked and set valve clearance
-Checked and set ignition coil clearance
Current mods:
-Throttle pedal installed in place of the original throttle lever
-Stiffer spring installed on the governor
Some things I noticed...
-When spinning the engine over I noticed that the intake valve seemed to bump open and close a tiny bit after its normal cycle. I don't know if this is some sort of feature for this engine or if something weird is going on with the cam?? (See video below)
-It appears this motor was originally equipped with the solenoid on the carburetor fuel bowl but when I got it the solenoid was gone and the bolt holding the fuel bowl on looked a bit odd, it was threaded on the outside to and had a small allen set screw inside it. I ended up replacing the fuel bowl, gasket, and bolt and the bolt supplied with the new bowl was just a plain bolt. I am not sure if the original bolt was special or needed?? (See pictures below)
Anyone have any ideas? Does this carb need modification to get anything over stock mower RPM??
Valve opening video:
http://youtu.be/fDKIyyLohwg