checking idle speed follow up

I finally put the theory to the test and check if i could get a meaningfull rpm reading from a frequency meter on a multimeter (£8 on the bay).
well... i guess it does work.
stuck the negative probe anywhere on the frame, and the positive somewhere by the spark plug, on the head. Result !
where before the reading was fluctuating randomly, i could get it to stabilise on 10Hz first, which climbed to 17Hz, as the bike slowly warmed up. (i stopped there, couldnt be arsed to wait 20min for the bike to fully warm up.)
if the maths is correct, 10Hz corresponds to 600rpm (realistic on a cold monster ????)
17Hz is 1020rpm.
i reved the engine, and got readings at 150Hz (9000rpm).
this is where i would possibly question the measurement. i am not sure if the monster will actually go this high, and i am sure i didn't open up the gaz completely either.
The meter takes a few seconds to stabilise anyway, which explains the possible duff reading at 150Hz. (i didn't rev up for long enough to get a stable reading)

conclusion is: using a fairly basic multimeter with frequency reading, it looks like it is possible to measure your idle speed,
without connecting a proper rev counter, or disassembling anything. Having said that, you will probably get better measurement if you make a direct contact on the plug's cable core. (somehow, only a particular cooling blade on the head, near the spark plug would give me a reading. the next blade didn't show anything...the joy of electromagnetism !)

anyway, i thought i'd share this REALLY important piece of information. I am off to celebrate this at my local.