I have used 18lb springs before and gained around 500 extra rpm but there was a noticeable decrease in power getting up to speed. The force needed to compress the springs sapped power from the engine. I will see if I can put something together.
The arx 3910 is the spec plug for the LO206 racing class, they use it because a smaller gap can manipulate the limited magneto, only allowed to turn 6100 rpm and if you go tighter than .018(spec, even though some of the stock plugs can be found tighter) it can allow it to over rev and give an unfair advantage in the spec class
Good video. The autolite is supposed to raise compression because of all the extra bulk around the plug which could possibly add power. I wonder what an already high compression head would do paired with an autolite. I'm running autolite and NGK on my minibike and cant tell a difference by feel but maybe I'll do a 0-60 test and see what the clock says.
Yeah that’s a good question. I would think I would have seen a difference with increased compression here as well but something else with the plug setup seemed to result in a loss greater than the benefit of increased compression.
@jwsbackyard6413 you're probably right. It'd be interesting to measure head volume with a regular plug and with an autolite and see how many ccs it's worth.
Goes to show that nothing is black and white. Sometimes context matters. The Autolite plug very well may perform better in certain applications, with certain modifications, under certain conditions (or not). It didn’t perform better in this specific situation though.
