So I buy a Honda CR500RE, I read-up on them, "oh they are the ping-king", ok so I get the head machined before I even ride it, first time out on it, it pings like crazy after 2 laps of the track. Hmmm I thinks, sounds lean at part throttle BUT it starts cold without the choke, Hmmm tells me it's rich on the pilot. I pull the plug .... blaaack.
So I figure it's lean on the first part of the needle, so I buy another needle with a smaller diameter first half, still has the same lean ping! Hmmmm (deep thinking again), so I sand-down the needle to make it real rich, it still pings, then blubbers and fouls a plug!
ok I think maybe slide cutaway? I gets the big file out and go to town on the bottom of the slide to reduce the amount of cutaway slide (making more rich) :-) So I've whipped about a 1mm off the slide, still pings like a bitch! There is no wear at all on the slide, looks new, and is still the standard 3.5.
There are no air-leaks anywhere, not the manifold, not the base gasket, the compression ratio is no higher than standard even with the squish closed up to 1.2mm.
So I think ignition timing, I read that the extra turbulence from a closed-up squish can cause the flame front to travel faster, maybe at that certain rpm/throttle position the CDI advance curve has more advance at that point, combined with the faster burning combustion chamber, causing it to ping? So I slot the stator backing-plate (so I can rotate it in the direction that the rotor travels), first 1mm, then 2mm, if anything it seems to run/ping worse, so I go back to standard position.
Now I've partially fixed the problem and now know what is causing it, I'll just see if anyone else thinks they know what it is before I tell? ;-)
