spark knock?

[no limit]

can someone explain what spark knock is and what exactly causes it and how to get rid of it?

[2004exrider]

spark knock aka pre ignition is when the gas is burning because of the compression of the engine and not the spark plug. to get rid of it you should run 93 octane, the higher the octane the harder it is to burn. thats why quads with 12.5:1 compression have to run high test gas.

[no limit]

i have a 12.5 -1 wiesco 440 piston, i started off running premium unleaded and it ran good but had a slight bing to it under accelleration so i started cutting the preium with 100LL aviation fuel, i added more and more until it went away, which was 70%prem. 30% av. gas it ran good for about a week and now it has what i think is spark knock, it only does it under load and when its hot. what can i do to fix this? i tried running straight 100LL and it still does it

[2004exrider]

try 110. are you sure its spark knock and not the rod by chance?

[no limit]

what would be wrong with the rod?(stretched, bent?) how would you tell exactly? i plan on tearing into it soon but if the rod is bent is it gunna be noticable or just out alittle?

[2004exrider]

it could be the rod bearing or wrist pin on it and the piston has play in it. sounds more like its spark knock though, try a higher octane.

[no limit]

the head has some porting done to it, it has a stage 1 hot cam and a 12.5-1 440 piston. what would be a good octane level to shoot for ?