no not going off plug colour but actual temperature readings, I've seen that when revs are high on dual carriagway or motorway the temperature never seemed to stop increasing. I checked the crank seals OK put bigger and bigger jets in but never seemed to get a good plug colour or a stop to the ever increasing temperature, so I had to find an answer ...I have a float valve with a stiff spring (nothing wrong with that per se) but that...coupled with a float height more than 21mm made me think that perhaps the fuel level drops enough in these high revving situations to actually uncover the tube that the pilot jet sits in...that would allow air to be drawn in to the intake at that point in time and may be the cause of my overhating...other evidence was a slight 'hanging' of the revs when exiting the fast road/motorway...yeah quite posiible...it's quickly settled...well it would wouldnt it, as the carb fuel level rose again due to the reduced load
well thats my theory, I really hope I'm on the right track with this because I'm out of ideas after this
Oh another clue is that I have never been able to get a sensible plug colour lately It's always been a bit washed out and not a definite colour, any shade a brown would have been nice but Iv'e seen it brown (ish) but with a whitish on the opposite side even with big jets in
high temperatures I have seen 230C after a short blast down the motorway, I actually saw 250C on a long dual carriagway trip during last years 2 stroke day from squires...not funny!!!