Maybe it's always done it, and I haven't noticed, but I don't think so.
Anyway, lately my AR seems to briefly open the powervalve right up for a second or so, before closing it at again, just above tickover.

As I pull away, the exhaust note suddnely becomes a lot deeper (and a bit louder), the engine feels like it will stall, then everything goes the way it should be. Happens especially just after the bike is started.

My first thought was a sticky valve, but then why would it open right up?

Anyone had the same, and got to the bottom of it?

mine does a very similar thing until it has cleared all the crpa out of the engine, don't think it is the powervalve, think it is either becasue it is running rich or too much oil sitting in the bore. once I have blatted it up the road 100yds or so it clears then engine and all is well. but if you pootle around on half throttle it doesn't clear.

My Nitro fueled RC car makes a similar deeper noise just when it gets to the point of stalling when the mixture needs turning down a bit.

Thanks Phil,
I can stop being paranoid about my ECU being on the way out then!
Is the jetting just a case of trial and error, with a plug chop after each change?
I'm using a full DEP, standard jetting, and the oil pump set according to the manual.
Or maybe I just don't ride hard enough? (Sorry officer - if I ride any slower it oils up!)

they do act a bit strange when not warm. in fact the cdi box is not set optimaly, i think admin said a mugen one sorts it out

i've only changed oil once in 2000km, never had to pull the plug and haven't checked anything else

it gets oil, chain lube and 2stroke oil.