hello i have a briggs and stratton 15.5 hp ohv on a craftsman 42" mower. the carb on it sucks shut when its running and it wont open up when you throttle up. when the mower is off the throttle moves just fine but as soon as you start it up it sucks shut again. if i reach down and close the choke the valve will open up. i have adjusted the governor arm i have replaced the crank case gasket as well as the rocker cover gasket. the head gasket looks almost brand new. i have tried adjusting the idle mixture screw and no change.
Sounds like you have the linkage hooked up wrong. When you move the throttle control does the throttle move to fully open and the choke to fully closed. That's what should happen if hooked up properly. When you pull back slightly, the choke valve should open. The governor should be trying to close the throttle and there should be a spring trying to open the throttle.
yes it is hooked up correctly when i take it all the way up the choke engages i know alot about small motors i just have never ran into the problem of the carb sucking shut when it runs when its off the linkage works properly and if i close the choke with my hand when its running the carb will open up it has nothing to do with the linkage
Is the spring opening the throttle when the engine is off? The reason I ask is that the throttle spring pulls the throttle open and the governor closes it. Sounds like there is no balance point.
when its off yes the throttle linkage works fine it opens and closes the carb like it should but as soon as i start the motor it sucks the carb shut and the only way it opens when its running is if i chock the carb by hand then it will throttle up. i mean i can reach down and pull the linkage by hand it it will rev up. the only thing that i could think of is that its sucking air in somewhere because it doesnt die when i block the airflow into the carb completely off
Sorry to say but I think you have the linkages reversed by what you are saying. There is no way an engine will speed up by closing the choke, it's not possible.
ok listen the throttle will only open when i reach down push the choke part way shut when it is wide open and the motor is running something is sucking the the carb valve shut do i have to take a video of it and post it for you to understand that . when the motor is of the linkage will move the carb just like it is supposed to i know its not hooked wrong because like i said i have a lot of knowledge on small motors and i have another mower that has almost the same motor and its set up the exact way
im not trying to sound rude im just trying to tell you that its hooked up properly and i know that it is i just dont know if it a vaccum leak could cause the carb to suck shut and it still keep running or if some one has had this problem before and knows how to fix it
#10
midnite rider
If you think you have a vacuum leak somewhere maybe take some WD 40 and spray around gaskets while running and see if it revs up to confirm an air leak. Just a thought that may help.:confused2:
sprayed around gaskets and didnt notice any change going to pull the motor off and check the governor to make sure its working correctly and that the waits are still in place
I understand your problem. i have a same/similar problem with my engine. i thought of checking the governer but that seems like i need to take the engine crank apart. my engine will idle fine. but soon after i advance throttle, it will want to close (suck) the butter fly valve. Thus resulting in engine RPM going up and down.
#16
SONOFADOCKER
Spray bottle with water - spray around carb bolts and the manifold and exhaust flanges and see if the motor smooths out - seeing cracker manifolds lately .
Is there a photo/drawing of the carb/governer linkage for the 15.5 available anyplace online? there is a small spring on the governor lever that I cant find a connection location for.
#18
Carscw
If you don't find one I'll take a pic of mine and post it here for you in the mourning
I think I read that you adjusted the governor. Not everyone knows how to do this correctly. The correct way, for those that might not know, is to have your throttle control (on the machine handle) to the SLOWEST position. then while looking at the governor shaft and arm on the engine block, have someone move the throttle control (on the machine handle) all the way to fast/choke position, and observe the rotation of the governor shaft and arm under the spring tension of the gov spring. While in that fast/choke position, loosen the governor arm (with the linkage on it) that is on that shaft and rotate the shaft AS FAR AS IT WILL GO @ THE "SAME" ROTATION as you saw the shaft and arm move when going from slow to fast. The throttle control must remain in the fast position while doing this to keep the integrity of the gov arm to throttle control arm in tact.
