Restoring Robbe Nova Cuatro with Webra 91 P-5 engine

[Turbonator]

This Robbe Nova Cuatro has been in storage for 11 years! I serviced EVERYTHING on this heli, and must say despite its years its still any absolutely beautiful machine!
The Webra motor I'd like to keep because of its historical value. Needless to say the bearings had it, as the ring was stuck inside the piston. I replaced the bearings, and managed to free the ring. Unfortunately the rind bended a bit. I worked on it for a few days to get it as perfect as possible and reassembled everything.
This old motor idles beautifully, and is very responsive, but it has one gremlin I cannot get rid of.
The motor keeps high operating RPM for a few seconds, and dies instantly all of a sudden. Tuning the low and high needle has got little to no effect on this problem.
Please help me to save this piece of Austrian history. I've added a YouTube link that demonstrates the issue at hand.

[danie.e]

Contact MECOA in the US - they will be able to supply you with a new piston, sleeve and ring for the engine. Get fresh O-rings as well and your engine will run like new.

[DustFlyer]

Hi,

Just an idea, maybe there is a restriction somewhere in the fuel supply line to the engine or the line feeding exhaust pressure to the tank. Enough fuel for idle but not sufficient for high rpm. Also have a look inside the tank.

Regards,
Nico

[Trex600]

Sounds like the fuel is restricted for the Hi RPM range.... Remove the needle valve assembly not only the needle valve and check for any blockage. Use compressed air to blow it clear if you see something but you can still blow through it anyway. If you do go the Danie.e route then you may as well change the bearings too, then 95% of the moving parts have been changed When it is sorted please let us know what you found the problem was...