Bike stopped recently on hot day and climbing gradient. Forum gurus diagnosed H E sensor failure but phrased in terms of the coil insulation breaking down. i know the H E transmitter is under the tank but that's miles away fr the coils. So confused.
yes, i'm on Clymer p 264 but that doesn't exactly explain the interaction.
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I'm about to put a blanket on top of engine but the last thing i want to do is exacerbate engine heat retention so it obviously has to go under electrics. 

Seems odd that over on Motobricker, Op Sonnu has shot of foil being laid fr steering head to back of seat OVER TOP of electrics

http://www.motobrick.com/index.php?topic=460.msg20030#msg20030

but anyway i need a reasonably simple explanation of what is going on with the K electrics so that in the future I can get the nurse at the old folks' home to do any fixing.

The HE sensor is at the front of the engine behind the T shaped plate with 5 screws and right at the end of the crankshaft. HE sensor work like points and trigger the spark making process. They connect to the Ignition Control Unit ICU which is under the tank right behind the steering head (alloy box about size of a cigarette packet) it processes the signal from HE sensors and sends it off down to the coil to be made into sparks.
The ICU needs to be kept cool which it is there in an air stream well above the radiator and away from the hot air stream, most important not to block air flow from it or you end up with deep fried silicone chips.
Usually when the HE sensors drop their bundle they will stop working when the engine reaches operating temperature and then start working again when cooled off, the engine doesn't need to get extra hot to kill them but things like that have to show up at sometime so why not when it is most inconvenient.
My wife's K75 showed up first as an intermittent miss when those sensors packed up.
As for heat getting at the rider I never found a way to really control it. I fitted a small automatic transmission cooler in front of the radiator to keep the fuel cool and therefore the tank was prevented from burning my legs which helped a lot.
If you get a chance have a look at Japuntes' K100 (he is a member here from Venezuela and made some very big side covers which control the heat to the riders legs.

So are you saying that if a foil blanket is put in on top of airbox, it is best not to have it extending forward right up to the top edge of the radiator but rather have it stop short so that the fan generated airflow can pass up and over the electrics. 
The tank has a foil liner already but the engine heat going out sideways on to ones legs on a hot day can be fierce. That's why I want a blanket over the engine and maybe having 50mm dropsides. I don't remember my K75 being anywhere three quarters as bad.

Try to keep it separated from the hot air that comes out back of the radiator but one of the first things to do is make sure all the foam rubber bits are in place just as factory designed then, that will keep a lot of the hot air off your legs.
When I first got my K 100 it had all those bits plus more in a box and the guy told me how hot they are to ride in summer.
When I reassembled it I went to great lengths to get it right and like I said the hot tank was the big problem. I have never fiddled about with the johnny blanket concept because I never had a big problem.
If you need any of the rubber bits I have quite a bit of that stuff here.
Charlie and some others have left the fairing lowers off and that makes a big difference, I used to take them off on the R80 and it made a world of difference but of course the feet still got cooked.
My brother had a pic of me out near Tibooburra standing in a cattle water trough trying to cool my feet on one of the Adventure Riders runs in 2005.

Rick, pretty sure I have all the rubber bits but will have to compare with Clymer

yes, when had lower off today, was wondering just what the effect of leaving it off would be.

What i think I am hearing you say is : don't allow radiator air to get up to electrics. So i can carry foil right up to top of rad, Correct? (like a barrier between 2 floors of a building)

If you do leave them off you need to strengthen the mounting brackets. Charlie knows what needs to be done there as he has done it.
Try to stop the hot air getting up among the wiring etc.