Hi All
Always interesting to see all the comments on spark and brand names.
Clearly Rotax is in a bind, NGK will not allow the use of their spark plugs and connectors on aviation....period. If you do so it is at your own risk and you must accept whatever consequences there are in the end. As an example in an accident it would be noted by the investigator and while it may not be related to your failure i can assure you the interpretation is you don't follow recommended maintenance. I have done a lot of work with TC in Canada and also NTSB in the USA as an expert. So that said what is the actual risk, in my opinion.
The only downside to the new plug and connectors is cost. They work great and indeed do give you double (at least) the time between changes. The duall ground splits the spark time between the centre pin and the ground bars so they wear much more slowly, hence double the time to wear out. The new PVL caps are essentially the same design internally as the NGK with a 5K ohm resistor so not much to worry about there.. The rubber is a bit better and should not be an issue at all. So far since there introduction I have not seen any rash of failures so can assume they are pretty reliaable.
As to not mixing up the new plugs with old, of course that just makes sense. Using all the same connectors also. I am not sure about both connectors and sparks have to be the new type. It would seem if you have an old engine and the connectors are good you can install the new plugs without a problem. If however you need to replace them it is a case where Rotax can't sell you the NGK so in their mind that is the only option.
As far as cleaning the plugs we have a mixed bag of speculation to old school beliefs. General Aviation plugs , the giant ones with huge ends and ground straps, were also expensive even a long time ago. The practice to save money was to clean them, repeatedly. This practice with our very small plugs is a big mistake in my view. The issue is they can remove the lead deposits but in doing so they also errode the porcelain portion of the tip protection and tiny "beads" of glass get trapped in the plug nose. The surface from glass bead particularly creates a slightly rough surface that simply collects lead much faster the second time around. The normal way is to just brush them off with an old toothbrush to remove any visible deposits. Unless you have misfiring spark that should be enough. The question of what material to use if you insist on a "blaster" type cleaning is simple. Use material that you would depend on to not damage critical parts. Walnut shell has been the go to media for that for decades however it is not uniform and tends to still into small gaps. The best for anything delicate is Sodium bicarbonate, (baking soda) and shoot it at no more than 60 PSI. This is the normal material for pistons, piston ring grooves, electrical wiring stators and all sorts of things that demand no deformation of the base materials. Anyway that's what I do.
Cheers
