Any of these articles contemplate the effects of high head temps or just the compression factoid?

Reelthing wrote on 08/21/08 at 15:31:04:






Lazy-lazy-lazy!!!  I go to the effort of researching all this and you want me to re-read it and answer your questions? Seriously though, please read it...it won't take long and there is much good stuff to learn.

Reelthing wrote on 08/21/08 at 20:05:03:



Okay, okay.  To summarize, an engine cannot use a higher octane gas than it was designed for, assuming you have it correctly tuned, and assuming you have not raised the combustion temperature by running the engine too hot.  Example:  if the fuel mixture is  too lean, then the combustion temp will be hotter than it was designed to get, and you will experience pinging/knocking.  Higher octane will help alleviate that problem, but the solution is to adjust the fuel mixture correctly.  Or, if you idle your air cooled engine too long stationary, the engine will overheat and the combustion temps will raise too high, and you get a lean condition.  Or, if you insist on lugging all the time, you may get the pinging/knocking and the higher octane will help that.  Or, if you have your timing advanced too far, again the higher octane will help alleviate the pinging.  So, unless you have a lean fuel mixture or a timing or overheating issue, or the combustion chamber is fouled with glowing red carbon deposits, a stock engine will see no power difference using a higher octane than the manufacturer recommends.

Reelthing wrote on 08/21/08 at 21:11:58:






And that is exactly why I always use Chevron Supreme in my bike.  It was 113 here, last week at 550' above sea level.

mick wrote on 08/21/08 at 21:27:49:







Keep in mind, now, your engine is no longer factory stock.  You've made changes to its mixture and breathing.  According to the links
I've listed and many more on the 'Net, manufacturers' octane recommendations are for an engine with no alterations.

yes - we still bump our head on the rpm - the '95 is sort of stock - jardine, carb tuned over many hours of plug reads, ir plug, and maybe a tiny bit more air - but still the rpm head bump - the '02 is kind of a different deal with the near open supertrap, long duration cam, and close to 0 air restriction - might do an extra 1000 rpm - but man is it ever screaming - even with a higher flow head, coated cylinder, oblong the time'n trig'r hole to advance it, and this carb ready to go on it - the redline is near the same - you just get there a lot quicker - need the chain drive on it I guess - wonder how the shaved head worked out for kawie10(?)

long gone mostly - even with teenagers and their cars - most "soup" them up with stickers, wheels, and shiny stuff - don't know a water pump from an alternator - where did the know how go