Did the stock rt1mx pistons only go to .5mm oversize? And I wonder if they had a taller compression height, vs the enduro pistons. That would explain the whole issue here, and why this thing runs so f-ing good now with the squish corrected. Don't mind me, just rambling more nonsense.. lol.

MX pistons aren't shaped higher to raise the comp, it's all in the head.
Piston crowns are All the same shape RT & MX.
Measuring the squish isn't straight forward as the piston shape doesnt follow the head squish shape so you'll get an increasing measurement very soon away from the edge.
On one of my failed projects--well it ran good but not a firebreather--.
Trying to think what did do.
Think i took a bit off the top of the cylinder although in hindsite i think it was when i was fafing around changing cranks trying a 250 crank but when i reverted to a 360 crank after shortening the cylinder 'for 68mm 250 stroke' i had the piston out the top with the 70mm crank. So i made a base plate which was 5mm thick but needed a bit more.
Think i'd machined the head down to the fin too for the 250 stroke experiment.
So i machined the 360 piston crown to match the squish all the way across as was protruding above the cylinder by a mm or so.
Piston was very dome topped & comp was up there too.
Looked a bit stupid but she ran good on std porting although theoreticaly porting was artificialy sightly raised.
Sorry if i lost you after the second sentence haha. I recommend that you "Don't do as i do".
Might have a video of that running but had horse & cart piston clearance so ignore that & don't think i gave it a big rev either unfortunately.

Looks like i gave it a bit of a rev. Very hard to watch sorry.
I remember now i had the dt360a stator with source 'only' & a suzy RG50 coil with box combined. No timing, just hooked it up, one wire from the sourcey thing to the 'coil with box' & rode off into the sunset.--Well--wasn't game too lol incase i had to walk home.
I'm sure i ran it in my RT2 360 rat bike roller but was all top end & not nice with the horrible trail ratios.
Anyway, forgotten where i was going with this, apart from nowhere.

Kind of lost me rt325, but that's OK!  I know I do the same sometimes, lol. Cool video BTW, I like your builds!

Found a 1.5 slide in my stash of parts. Threw it in this morning, and the pre ignition/ping is now 95% gone! Hit that one right on the money Markt, thank you!

You could also try a slightly larger pilot jet...  and while 1.5 turns is "standard" on the air screw, I've had some modified bikes that liked 3/4 turns out best...  (the idle wasn't best...  the transition off idle was much better.  I was racing so throttle response was much more important than a crisp idle.)

Copy that!  I've got a 60 pilot currently, at 2.5 turns out.  I'll nudge it back in to 1.5 and see how it goes.  It definitely acts richer now on the idle circuit.  I've been setting the idle to the point where it is so low it will die in a second or 2.  Throttle response seems the best like that, and it doesn't pop/surge when you let off the throttle.  Definitely a touchy motor lol.

www.vintagemx.net/1970-yamaha-rt1-360-modified/

Found this again, thought it was cool.  And similar top end to what I have.

Shoot I deleted my last reply. I was curious if anyone has ever seen port dimensions listed for the rt1mx? I can find mx360 dimensions, and they measure out very similar to my rt2mx cylinder. The rt1 "mx" cylinder has drastically lower port timing. I measured, over 5 mm difference. And compared to an rt3 cylinder, I still believe it to be within only 1mm difference.

Just wanted to update my progress. I actually ended up dropping to a number 40 pilot, likes about 1 turn out. Was overly rich down low after the 1.5 slide change. I also pulled the 6dh2 needle up, to the 4th position.
Runs flawlessly.
the best part, it's not pinging anymore! The last adjustment to the needle really helped.