Hi!
When an engine quits at full throttle opening .....be it in the air or on a test stand ...it is 95% of the time because of lack of fuel!!!
(it could be the glowplug and other factors too but if you have a new engine never before disasembled with a fresh glowplug it is certainly lack of fuel!)
Lack of fuel means : either the fullspeed needle or the idle needle is set to lean...on MVVS engines with old 3216 and 3219 carbs the two needles interact!!! Lack of fuel also means that the temperature inside the engine gets to hot ...from running the engine on wrong fuel (to much nitro), to large prop or wrong glowplug....or a leak somewhere!
MVVS engines work good on fuel containing 0-10% nitro...if more is used than shim up the head somewhat (0,1mm or more).
On a .21 MVVS with minipipe a 8x6, 9x4, 9x5 or 10x4 APC is okey!
A 9x4 will rew apr 16000rpm using 10% nitro and 20% castor oil
using a Rossi 5-6 glowplug!

This engine could also be used with the two MVVS silencers..giving a much nicer sound than the minipipe!
What is your set up?

Regards!
Jan K
Airracing Products
MVVS importer Sweden