Here’s the latest: The latest carb kit arrived yesterday, so today was the day to put it in. As mentioned earlier, I had pulled the carb off already and cleaned it up as best I could, but still no change in the engine stalling out after a few minutes. Today, when pulling the carb off, I took extra care to check everything that could be disassembled for any plugging. None could be found except the high speed jet had some debris stuck at the end of the long removable tube. As I was replacing it with a new one, any potential issue with that should be eliminated. Otherwise, all replaceable components were replaced, the carb reassembled, the pulse line double checked for vacuum and everything put back together properly.
After reassembly, the adjustable valves were pre-set to start the engine. It started up after a minute of cranking. I then adjusted the slow and high speed valves. I noticed that when I flicked the throttle, some bluish smoke came from the exhaust, but this mostly disappeared once the high speed jet/valve was adjusted to it’s best setting. But, one strange thing…..every few seconds, a single misfire would occur while the engine was running at normal high operating rpm. Same at low rpm. This was abnormal for this engine, as it typically ran smoothly with no misfires of any kind.
Thus far, the tractor was sitting outside the garage while I was adjusting theh carb while the engine was running at high rpm to adjust the high speed valve/jet, which the manual refers to as the “needle valve”. Since forever, I have used the term “needle valve” to refer to the float operated valve with the neoprene tip. Apparently, I have been using the incorrect term forever, but I will continue referring to it as the high speed valve/jet here to avoid any further confusion to what I am describing.
So….after letting it run for a few minutes, I was about to head back inside the garage to get a shorter screwdriver for making final carb adjustments. Suddenly, the engine stopped. Huh? Hopped back on the tractor and cranked the engine over for another minute, but absolutely dead and wouldn’t fire at all.
Ok, now time to use the newly acquired spark tester, an Oregon model that is shown in the photo. Not having used this type before, I wasn’t certain how to hook it up, but I hooked the clip onto the spark plug and inserted the bare road into the spark plug wire. Not sure what that third rod is for, but it sticks into the spark chamber of the tester with it’s point less than one millimeter from the bare rod. Anybody have one of these and know what that third rod is for? Anyway, I cranked the engine and not one sign of spark in the tester viewing window. Okay, let’s wait a half hour, then see if any spark. After a half hour, I cranked the engine over again, and saw a super faint spark shoot across the window. Continued cranking for another thirty seconds but only saw one or two of the same barely visible sparks shoot across the viewing window. Otherwise, nothing.
So, this mystery has evolved yet again, kind of. Why I had been able to restart the engine the last time it ran, but only by choking, is strange, since now it won’t start at all. Now, I am back to thinking about the coil, as this was one of the initial suspects that I chose to not pursue (this would classify as ”denial” since I really didn’t want to think about having to pull the engine from the tractor to replace the magnetron behind the flywheel. I’ve had this engine out twice before when the welch plugs fell out and caused the engine to suck in dirt and ruining the cylinder wall, and didn’t want to think about going thru that again. But, since I have already replaced the condenser with no improvement from doing it, the coil remains the final suspect. Unless a scuffed or broken wire has shorted the ignition out. I can’t see any externally, so likely will be removing the engine for the third time. If so, it won’t be going back in until it’s been to the rebuild shop to have a leakdown and compression test, then most likely an overhaul that may include a rebore. Not looking forward to the next chapter…