Yup, I tried the CEK-3/38 last year, and it was less wild then CEK-2 or CEL-2 /38, but evidence from sound, smoke and plug suggested it could run cleaner.
The CEK-2 (as well as the CEL) is a handfull if the revs creep up, it pulls hard and begins to care less about where the throttle is set to. 1/4 throttle pulls about as hard as 3/4 throttle until the revs climb above 6-7k or so. Could be fun in the cornfields or for an agressive rider, but I'll hurt myself in the woods. I'm accustomed to more direct control. The bike would spank a novice.
So the aim is to get more linear throttle control without turning it back into a spooge factory.
Also, speaking of throttle responce, its as if I have a binary throttle up to about 2 -2.5 kRPM. It has become more significant since straying from the 1173,
Off idle, it pulls up to this threashold at a very constant, dull torque, extreemly independant of throttle position, (as long as its off-idle). Then it kicks in, always at the same rpm, throttle response is there, and pulls hard.
AS and needle adjustments affect the strength of the engine in this idle-2500 range, but not the rpm that it transitions. So setting the AS optimally can get me through and over this transition sooner, but not affect the rpm it occurs.
This has made me suspect of the DF1 valve.
CC, do you remember the symtom that made the DF1 valve a flop for the KDX application? Any resemblance to this weirdness?