You can get similar size CR500 upgrade cylinders
Really? Madness, yet appealing.
Like many aging man children who have hit their heads once too often; I have long had a place in my heart for a CR500AF. (E.g. Service Honda) I think it's a case of nostalgia and wishful thinking v reality.
Interestingly MXA said the latest MX 250 2 strokes from KTM/Husqvarna might be too powerful. (They can be tamed somewhat with the power valve.)
I read another report where a 300 conversion on a KTM SX250 (pre 2016 model) was returned for "de tuning"! (Apparently using an enduro spec barrel and maybe ignition timing is recommended for anyone below world championship speed who desires an open class 2 stroke MXr.)
I guess 2 strokes would be even more advanced if they hadn't been killed off by class rules in many disciplines.
My next bike is likely to be one of the new 300 2T Enduro bikes. Can't beat the light weight and the exciting but predictable power delivery (no random 4 stroke hiccups.)