Please read my article in aeromodeller No 929, September/October 2014.
Complete backplate set for ED Racer. If you happen to have a spare PAW2.49RC needle valve assembly you can try this. It is a variation on the throttle barrel that I didn't try, I measured a PAW NVA with my caliper and drew a barrel. Main difference is the diameter of the spraybar; it´s about 3.6mm instead of the 3mm OS PET099. I may have it wrong. This rotating valve makes the engine run in normal counter clockwise direction. The fuelmixture enters the crankcase through a slot between rotor and backplate. Chamfer the edge of the slot to minimize resistence. Centrifugal force does the rest. A rotating valve that does both directions is available. Just ask. Use cheap thin cyano so the material can soak it up. Keep it in the fridge and apply it cold. Don't block any holes with it (especially the pinhole). Apply the glue in two stages. In the second stage apply it where your fingers were in the first stage. Tip: when mating the backplate with the engine insert the rotor first. If you need just one part you can contact me and I'll make it available. About colour: You can easily dye it yourself with a felt-tip or marker pen that you loan from your kids. The print will soak it up like a sponge. But do so before painting it with the cyano. The cyano fixates the dye. Works OK. So there is really no need to order black plastic. Disclaimer: You can use these products at your own risk. I have a job, not a business. I do not make any money at all from these designs. Please correct me if I'm wrong. Be so kind to share your experiences.