Hi I have a old Briggs and Stratton Model 92908, 1717, 0178121508.4 stroke with automatic choke i have replaced the diaphram and guvnor spring and it starts first time but it has trouble when i try to increase and control the throttle sometimes it controls it but then it will go crazy and either just stay at one speed even with full throttel or rev up and down..is this to do with the unleaded petrol i am using or more serious??
Thank you Steve.

Steve C, September 2008

Sorry!! Thanks Phil.

Steve, September 2008

Thanks Paul i will try this.
Steve

Steve, September 2008

Check that the auto-choke is free-movng - IE with engine off it should be lightly spring loaded CLOSED. If you pull the starter, it should 'flutter' in response to engine vacuum. If not, this needs to be fixed before proceedng any further

Remove air flter, then ;-

Second problem - I can almost guarantee that either the govenor vane is stiff move (there should be no resistance at all to movement, except for spring tension), or the spring is twisted or jammed.

Move the throttle control to 'FAST'. This should cause the spring to pull the carb throttle wide open. If not, find out why and fix it. If OK, check that the carb throttle can be closed by hand against spring tension with no binding. Again if not, find out why and fix it.

Start engine with filter off so you can observe the throttle movement. Top speed is set by bending the spring anchorage that is moved by the speed control. Tighter spring =more speed.

phil_saunders@bigfoot.com

Phil Saunders, September 2008