I am quite new to CRM ownnership but have owned many two strokes and was suprised to find my newly aquired MK250 had low end performance quite poor and running rough on idle.I took the carb apart to find the pilot and main jet oversize! fault cured i thought and ordered the correct parts only to find after fitting the new parts the bike ran even worse than before .Being puzzled by this i suspected an air leak and i decided to spray some lube over the intake area to find that for a few seconds the bike behaved itself. fault was found to be a failing reed block gasket and the previous owner had fitted bigger jets to compensate for the extra air being drawn in past the gasket.new gasket fitted and all is good,i worked in the motor trade for 26 years and using a spray lube etc to locate air leaks was a common trick
hope this is of interest.
chris

Good result .

This has been quite a common fault, gasket or perished boot, over last year or so. Some have used the testing method as you describe.

Good call Kreidler, hopefully others will see your post and do like wise .
Regards Mike