On the coast (sea level) in the sand (huge engine loads). Yes, I've been there before and I am not unfamiliar with jetting.
I've run a 160 main in prior dune trips with the -30 pipe, and the bike worked fine. The last trip, however a plug check was a tad lean for my comfort level although well within a 'very good' range. So, this time I put in a 162 just 'cuz.
A plug check when I first hit the sand looked fine (sorta..more later). No detonation (I've heard plenty of that, I know what it sounds like...when it's bad enough to hear anyway), no overheating. As a matter of fact, the bike was running terrific!!
They always do just before they blow up!
My recent suspension changes worked great in the sand where there were problems before, the bike could pull in 6th gear even when it was below its power band!
'This is going to be fun', I said!
Ten miles into a ride (all sand, all scream) there was that definite piston-port-sound.
I got towed.... in the sand (about five miles) by a quad even. Thankfully, too!
Here's the point. I was jetted correctly. I've run for days with leaner jetting on the same setup.
Except for one thing! A spark plug that was over a year old!
That was a mistake. When I looked at the plug (yes, for color) when I first got there, I did see but did not pay attention to the condition of the porcelain. Had I paid attention, I would have realized the condition of the tip was less that satisfactory and would have changed the plug.
Didn't do that.
The plug turned into an ignition source due to its poor condition. Ate stuff. Or maybe it blew up which made a sharpie on the crown that did the same thing.
Note that there is no metal flash on the exhaust, and the head looks fine with the exception of a mark or two from aluminum bits flying around. This happened in a heartbeat once the timed ignition source was defeated.
It was a BR8EG plug. That's a finewire, yes...but not an protruding tip that is a no-no in 2-strokes. An ES would likely have fared better. Heck..the center electrode in this plug is long gone! It's not just blowed off from the insulator fracture...it's missing way down inside the plug.
Lesson learned: Just because the plug is still firing, change it every six months or so anyway. Especially if you're going to max-rpm extended hi-load ops like sand.
I'm not sure I understand. What was the "condition of the tip" and "of the porcelain" that you should have noticed before this actually happened? I've seen many fouled plugs before but never one that started firing out of time(?) and came apart like that.