O-rings are faulty. Mine broke as I looked at them moments after I installed them !. HPI springs and thicker, better quality O-rings combination will work but reports are that the metal gear is weak at the welds and are braking. H-9 Cub gear appears to be a better solution. $78 bucks though, But I believe I'll order one. 87054 Exhaust Manifold springs are the HPI product number from Tower Hobbies if ypu want to try that combo. It certainly is much stronger. Great flying Cub, straight take-offs and landings [strange ] Seeya, MM