My Husqvarna garden tractor calls for a 5066 spark plug. The nearest I could find was a 5066K at Amazon, for six dollars apiece.
So I got a pair, along with air, oil, and fuel filters. Well, I got em because the tractor would suddenly stall out while I was using it. Two, three times it happened, in a month. Not a fluke, obviously. So I changed the plugs and the filters.
That was about four weeks ago, with 130 hours on the motor.
After I fixed it, it was hard to start.
Since I had the thing it always started easily, even with the engine speed lever down as low as it could go. But since I fixed it, I play with the throttle and try several times, cranking longer than I should, before it finally starts. After it starts, it is good for the day, but not as good as it was originally. Curse my luck... and curse my skill.
Yesterday (27 August) I went out looking for a new fuel filter. Found two guys that had one. Neither guy accepts credit cards. So I was at a loss. Got replacement plugs (Champion RC12YC, $2 apiece), got home, and changed the plugs. 187.5 hours on the motor. About 57 on the 5066K plugs.
If it is still hard-starting today, it's the fuel filter. If not, it was the plugs.
...
It's the fuel filter.