Bennie, the BR8ES or BP8ES is the standard, recommended plug by Rotax for your engine.
The BR8EA will not harm your engine at all. It has a V-groove in the electrode tip and is supposed to give better ignition with a better spark flame. It burns at a good temperature at any throttle selection. The theory is that if you've been at say, half throttle for a while, and you suddenly open the throttle, it will burn the sudden increase in fuel/air mixture effectively enough to respond immediately. It's a special racing engine plug that's why it costs around R55,00 each.
Picture of the EA plug:
I use the NGK BR9EIX plugs. It has a colder range and is also a racing plug. It has better ignition properties than the EA plug and can withstand fouling and leaner mixtures better. Just a little safety factor for my engine :D It also dissipates heat more quickly so the combustion chamber doesn't get as hot as with a normal standard heat range plug. The heat generated has to go somewhere though, so it is being transferred into the cylinder head where the radiator coolant takes care of it (582, water-cooled) :D
It also starts my engine quicker because the engine is inverted and is prone to wet-fouling.
They also cost in the region of R60,00 each
Picture of the EIX plug:
It's probably overkill for our application, but I feel better
The Agentman will know all about the importance of racing plugs :D
Duck Rogers