Well, you stumped a lot of folks. Stop the tease. Reveal the secret fix.
Well it was revealed to those know had do proper carburetor modifications. It down to a factory induced restriction in the metering of the fuel causing the engine to run extremely lean; therefore, the fuel load was igniting premature (pre-ignition). If I post the the complete details there are DIYers out there that will trying it on every carburetor screwing many of them up using these micro drill bits For them it would be better just to install the correct OEM carburetor. I do get tired of hearing that Nikki carburetor is one of the hardest carburetor to repair when it is one of the easiest.
Man that Slick 50 really works. Won't idle below 2500rpm.... Extra 16hp, having to run a NASCAR restrictor plate.
Now you are only trying to make fun of the problem.
Maybe I should never posted anything about this for the real mechanics to learn from such a problem. Yes it hard not to get distracted and keep going the same old worn path. Having an open mind when approaching is key to troubleshooting.
See what you started Star, a never solved thread.
Oh a suggested solution was finally got very close to heart of the problem. Post #12. For mechanics that know what they doing they know what I did when I resized a under sized jet.
The problem here I see is no one fully read the thread. Without reading everything it like troubleshooting with only half a mind working. You may not ever see that red herring as it is on another path.
It like the Husqvarna YTH2348 steering tie rod replacement I did last week. If I just keep trying to get a wrench on the backside of the sector gear I would not have realize they Husqvarna redesigned the area. What was once a 30 minute job is now a 1-1/2 hour job as the deck has to come off and the steering completely disassemble just because put a plastic cap bushing over the nut. So glad I brought the mower into the shop as it took a large impact to disassemble the sector gear assembly just to get that cap off. As always you get a face full of dirt when working under a mower.