I did some measurements on the Starter speeds. I used an external Prop Tachometer plus the BUDS Software to verify the engine speed. They tied up with the EMU Tachometer, although sometimes the EMU Tachometer wouldn't work.
The numbers were:-
Engine Cold (first start of the day). 240 rpm
Engine Cold + External Jump Battery. 480 rpm
Engine Cold with Plugs out (no compression). 240 rpm (I didn't try it with external battery)
* - Engine Speeds (Prop Speeds corrected by Gearbox ratio 2.43:1)
Tried starting it with the external battery, it fired on rear two cylinders ran for a few seconds then stopped, it took several more goes at starting it,
where it ran at 400-600 rpm then after 15-20 seconds it kicks into life and runs up normally to 2000 rpm. It continues to work for the rest of the day,
starting each time normally.
I measured the Voltage on Starter Motor, it dropped to 10v on cranking (I didn't get the chance to measure it with the External Battery).
Starter solenoid Ok - no Voltage drop across it while cranking (this is one item that was never changed when engine was replaced).
I think it is worth changing the Starter Motor before tearing the engine to bits.
I would have thought if the Sprag clutch was slipping, removing the Plugs should having reduced the load (compression) and it should have spun faster.
The sage conitues.......
Before pulling the engine to pieces to change the sprag clutch which I can't get my head around the logic of doing this, If it is slipping why doesn't the cranking speed increase when the plugs and removed ?
I am either going to connect a high current cable from a large battery to the Starter motor and note the Cranking speed. In the meantime I will try and obtain another Starter Motor to try.
