Question
throttle linkage
Eric, my Mountfield lawnmower throttle fluctuates up/down. Starts ok, but never runs smooth. i noticed the throttle control lever pivot spindle is rocking back and forth, causing the butterfly value to rotates slightly. you suggested it was likely to be due to a dirty/blocked carb, but after stripping this down and cleaning all the jets, there has been no improvement. this mower is a fixed throttle model, and i understand there is some type of balance mechanism that adjusts the throttle position as the engine rotates and warms. maybe this mechanism is faulty and causing the choke problem?
any ideas how i check this? i've taken the engine off the mower but it seems the only way to get at what’s behind the throttle spindle is to take the bottom of the engine off. i can do that, but would first like to know if i'm going in the right direction, and if so is this repairable.
engine RS100 - 100103651027 on a Mountfield SP414.
AnswerA few engines have a simple bi-metal sensor on the exhaust. The parts diagram for your engine did not show any sensor.
Have the valve clearances ever been checked? I can not find the valve spec clearance for your engine but I suspect it in the .004-.006 of an inch range.
Take a look at the link below, Overhead Valve Adjustment:
http://www.briggsandstratton.com/support/frequently-asked-questions/Servicing%20
Most all 4 cycle OHV small engines use the same procedure for adjusting the valves.
DO NOT adjust the clearances unless you know for sure what the correct clearance is supposed to be. Just measure the clearance and let me know what the clearance(s) are.
Are there any local small engine shops near you who might have the valve clearance specifications?
Eric
