Spark plug recomendation

[revilla]

[anthonym]

Finally? Maybe a night's sleep was required - sleepy posting is always risky. Thinking about it (that will be my enquiring ocd ) do all engines combust in a fixed range of temperatures?   so trying to put all the above comments into their context of actual temperature ranges:

Thus, we can conclude that machines can operate at temperatures higher than the melting point of its components. Thanks to the COOLING SYSTEM.

The maximum temperature generated inside a petrol engine can range from 1000-1200 degree Celsius and that is at the tip of the spark plug. The average temperature that is observed in the engine cylinder would range from 200-280 degree Celsius .

If it the heat range is too hot, your engine could experience detonation, pre-ignition, or power loss. Most spark plug manufacturers recommend that the tip temperature remain between 500° C and 850° C.

A cold plug has a shorter insulator nose length—the distance from tip to spark plug shell—and transfers heat rapidly from its firing tip to the cylinder head water jacket.

So we may be able to see by eye if a plug is hotter (longer nose) or colder (shorter nose) ?

So(2) I have a K R500 engine that is designed to run very hot (lots of power), and Minister (the builders) recommend(ed) a .9 gap using NGK BCPR7ES  . Given I do zero track time I do suffer mucky plugs and give them a bit of a clean to help the engine along. The reasons for mucky plugs vary, but all else being ok Minister used to tell me to always run at higher revs rather than lower, so given a choice trickle along at 4,500 instead of 2,500, such as in traffic, be in 2nd and not 4th say. The idea being to keep the plugs hot enough to clean themselves.

Conversely if I don't get or keep the engine hot enough on any given day, I could do with plugs that get hotter faster  / run more hot (MORE insulation) on that occasion; meaning plugs that get hotter (to their operating/self cleaning temperature) with a less hot engine. I could have different plugs for different expected types of day on tour; or just clean the plugs during a coffee stop.. 

so a less powerful engine, say 170bhp with plugs intended for a 235bhp engine will tend to UNDERheat THE PLUGS because .. because why.. shorter nose, faster heat dissipation, warm up too LITTLE...so power loss risk 

that just leaves the gap...  (assuming I have all this understood - fat chance)...

ok - handing this in for marking.