Question I have a very old Allis-Chamers garden tractor with a 10hp Briggs&Stratten engine. The other day while blowing snow, it backfired and quit. I have fuel, some compression, spark and a good battery. I own a small bodyshop and do most of my own mechanical work for close to 40 years. I don't understand these small motors.
Any clue as to what is wrong? I realize that it needs more than 35 pounds compression to run, but it has been running just fine until now.
Thanx, Mike
AnswerDear Steve,
I understand your machine quit in the middle of doing some work. What should be looked at is the root cause of misfiring. I understand that if a spark plug gag is too wide, then too much voltage is required to make the jump. Given that the required voltage is far greater than that supplied - then misfiring results.
Misfiring is the result of the ignition not being able to jump the gap or maintain the spark. A too narrow gap would require a lower voltage, leading to a rough idle and premature wearing of other engine parts. I think this would be a good place to start. Check the condition of the spark, see that the gap is set properly. Make sure the voltages supplied to the spark is adequate.
** I also work on my own automobiles & engines etc., and I've found that small engines are very similar to automotive engines, except they don't have as much computerized parts [sensors, etc].
Hope you find this information helpful.
Howard
