Spark Knock???

[ChevyBlazerBoy]

I justed pulled my tractor out for the first time (Craftsman YS4500 LE 22HP Briggs OHV) this spring. Before winter i changed plugs, fuel filter, oil. I seem to be getting quite a bit of spark knock while idling. Sounds like a clacking but I can't hear it while it is higher RPM's. I put the old spark plugs back in and the knock went away but then after driving it around for a bit it started making a little knock while idiling. I am running 93 octane fuel. Any idea's or could it be remnant of fuel stabilizer in the system?

 

[Fordlords]

It's not likely spark knock. What I hear happen a lot on these newer OHV small engines that have hydraulic lifters is the lifters tend to bleed down a little after the engine is shut down during the winter. It can take a good hour or two of running for the lifters to completely fill themselves back up with oil. Until this happens the noise (which is a clacking sound) is especially noticeable at idle, but they will eventually fill back up. Sometimes a little Marvel Mystery Oil added to the crankcase can speed up this process, but not normally worth the bother. If you run it up to full throttle for about 5 minutes and pull and examine a plug and it's tip is brown/tan, you'll know your fuel mixture is OK, and only that along with improper ignition timing could even cause a spark knock, and those are two things that are not even adjustable on small engines anymore.

-Fordlords-

 

[ChevyBlazerBoy]

Great, I will let her run for a while. Sounds exactly what my issue is.