Originally Posted by
Planemike
POBJOY....... Just as matter of interest are hose two engines now flying/airworthy...??
One (90HP Niagra ) still in airframe and giving makers oil pressure when laid up (now being ulaid). The secret with Pobjoys is to 'immediately' change the exhaust valves before they fail and ruin the guts. These are the weak links. The other item is the matter of the BTH mags running at nearly twice engine speed via the patent Pobjoy couplng. People get very pedantic and try to engineer any 'slop' out of the system which is totally the wrong measure.to take. The best way is to live with slop, lubricate freely, and time the mag allowing for the backlash. After I changed the valves, life (airshows) were pretty routine with just the odd mag spring issue, and a rather short display at Halfpenny Green when an inlet pipe popped off when the bolts decided to retire (threads stripped). This prompted a return to home mod utilising a bonding material and use of prop spec wire locking.
The other motor had been in the bottom crate and this had rotted allowing the cylinders to rest on the ground. Guts inhibited and ok but not needed yet, and has the very rare Rotax mags which run at half engine speed. No I engine ran fine on Australia attempt until rotor arms gave up over Gulf of Oman requiring a short 'holiday' in IRAN.