OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Carby Problems on Briggs Quantum engine

Hi everyone

I have a 3.5hp Quantum engine on a rover rotary mower.

I have cleaned the carby out, removed bowl, washed unit out and re-assembled. The engine now runs. It was missing the spring that connects to the govenor arm to the throttle, so I fitted one that I founf laying around.

You can start the engine, move the throttle to the run possition and the revs increase slightly. But it is not running at full revs. Will the revs increase when the mower is put under load?

I did try mowing my lawn, but as I mowede it 2 days ago with the reel mower, I didnt get any indication and the mower was not under any cutting load.

Cheers

The substitute spring you fitted is the governor spring, and it has to be exactly the right length and tension to work. The function of the governor spring is to try to open the throttle, and the mechanical part of the governor tries to close it. The speed control sets the amount of spring tension that the mechanical part has to overcome to keep the engine from running faster than you want. Since the mechanical part is winning the struggle, your substitute spring seems to be applying insufficient tension, because it is either too long or too light. The only practical cure is to obtain the correct spring. It is lucky the spring was too light: if it was too heavy you'd probably have a broken connecting rod right now.

To answer your specific question, the engine will not speed up when it is put under load. The governor's function is to keep the speed constant regardless of load.

Posting pictures would help.