I've had one engine failure and two power reductions after take-off because I've been too lazy to service the vacuum driven fuel pump. Didin't understand the warnings at first but do now.
Gradual raising of EGT at cruise power over months.
Because the diaphragm in the pump gets stretched it doesn't deliver its full stroke leaving lower fuel level in the float bowl and a leaner mixture.
Worst case is where you're on full chat at take-off. There's the least vacuum in the crankcase because the throttle is wide open and there's the most demand for fuel. That's when my 508 died and I had to land in a wood-yard just outside Breighton's boundary.
Getting high EGTs on the 503 again now.
Where's the best place to buy the correct service kit for our Mikuni round pumps in the US?
Rotax has a service letter for the Mikuni pressure pumps. If the pump pressure inlet is above the engine pressure port there is no problem. If it is below the engine pressure port there must be a weep hole drilled in the pump. This applies to both the round and rectangular style pumps. The diaphragm cavity can fil with fuel/oil over time and gradually prevent the pump from functioning. Usually the pumps from Team have this modification. The rebuild kits would not add this modification as the castings have to be drilled with a 1/64" hole. Please read page two of: https://m.cps-parts.com/cps/pdf/Part41.pdf for more information.
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