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flying high

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  • Location
    Sydney, NSW, Australia
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    google
  • Biography
    wife is the trainee pilot of gyroplane that has been rebuilt from a wreck, both flying happily together now
  • Vehicles
    EA81 twin carb engine in a gyroplane

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  1. Hello all, apologies for being so slow in getting back to this I've just been flat out. I went the hangar and checked everything I could including the cam and I concluded all was good. So that left me with only one thing to do so I started pulling it down. I intentionally removed the reduction gearbox first and restarted the engine. It purred like a kitten. So after all that time and fiddling about it wasn't the engine at all. I've pulled the gearbox down and found the sprag clutch inside had just started to fail. As the sprag is not available that's the end of the gearbox. I'll sort out the next gearbox over the next couple of weeks. Sincere thanks for the help, I learnt a great deal about cam timing and other bits and pieces so it wasn't a total loss. Cheers
  2. Thanks Dirk I was going to fumble through this process with a fair degree of ignorance, I expect that link will give me a much greater chance of success. I'll try to give a decent report after the weekend. Many thanks Phil
  3. Hi and thanks for the responses, I'd really like to hear from somebody who can tell me the running characteristics of this engine if the camshaft is re-assembled one tooth "out". Trying to do this in order, Jono, it didn't quite seize in midair , power dropped, oil pressure dropped, my wife landed it in a farmers paddock and it stopped just on landing. Carburettor done by old reputable firm in Sydney, I don't want to use the name, and yes I did block off the carburettor, an idea born in desperation which did indicate that either both have the same fault or neither has a fault. Standard EA 81 with twins. Carby's were done chasing the problem as they were not adjustable when adjustment was attempted. The twin carbs on the single manifold still need to be balanced. Problem was there from beginning after rebuild and did not change with the rebuild of the carbys so I would expect that neither carby has a fault. Dirk, my feeling is that it is in the electrics as well, one of the recommended methods for doing the timing in aircraft is to take it over 3500 RPM and set it between 28 and 32° before top dead centre, this amount of advance is considered safe. At this RPM the vacuum advance should not be doing a thing anyhow but yes you're right it could be taken off and possibly give me a slightly harder start but I can't imagine the vacuum is the problem as it exists throughout the rev range. The timing light flash onto the flywheel is rocksolid indicating that the distributor is not worn in the shaft and the advance does not change between 3500 and 4,000 indicating that the weights are fully extended. The distributor cap, points and leads were the ones off the old engine and were only changed trying to chase down the problem and they do look identical. I'm planning to go to the gyro this weekend with a vacuum gauge and the dial gauge to check a few more things. Jono, not too sure about the reliability of your compression gauge, those numbers do not fit with any of the aircraft rebuids I know of and somewhat out of kilter with my workshop manual. According to the manual my readings are high and the variance is well within range. Thanks, any more ideas?
  4. Hi, My gyroplane has an EA81 twin carb engine that was overheated to siezure and has now been rebuilt but it runs rough and does not develop the power it should. The rough running does not allow an idle below 1200 RPM as it causes the gearbox to chatter, previously it would idle down to 800 RPM. The engine seems to smooth out as the revs increase but the power is down as the new engine will not rev past 4800 RPM whereas previously it would go to 5400 RPM with the same pitch on the propeller. The engine was 700 hours old before this rebuild with compression significantly lower than has now been achieved. The work done Cylinder heads professionally machined and rebuilt, new valve seats, valves and valve springs Cylinder blocks decked, bored 0.5 oversize. New pistons and rings Pushrods checked for straightness Pistons, rods and crank rebalanced Camshaft checked, it is believed to have been mildly ground in the past but I did not measure it up when I had it out. Reconditioned carburettors with butterfly shafts bored and bushed, Hitachi carbs, float levels correctly set. New sparkplugs, distributor cap and points, points were set with dwell meter. New spark leads were not replaced as they were only 30 hours old. One lead measured high resistance and was replaced. All 5 leads were then exchanged with a set from another engine that is running well without improvement of symptoms. Alternator reconditioned. New oil pump Waterpump approximately 30 hours old. Battery is 30 hours/12months old and in good condition. Engine was rewired approximately 30 hours ago, some was heat damaged and repaired. Spark plugs,coil and points have been replaced yet again in sequence without improvement. Currently cylinder compression ranges from 175 psi to 195 psi. There is no water in the oil or other indication of head gasket issues. Ignition timing is set at 30° BTDC at 3500 RPM, this results in 4°BTDC at 1200 RPM (with vacuum line attached). Distributor has not been rebuilt but timing light gives a very solid and stable visibility of marks on the flywheel up to 4000 rpm, and was not tested any higher. Valve clearances have been checked and rechecked at 0.25mm inlet and 0.35 mm exhaust. I have sprayed carby cleaner liberally around all manifold and vacuum connections looking for a leak without success. I have balanced the carburettors with a vacuum meter. I have disconnected the carburettors one at a time and sealed the air intake forcing each carburettor to be the only carburettor in turn, no change in symptoms. Carburettor idle solenoids were disconnected in turn with a significant deterioration of the idle in both cases. I run the engine on 98 octane fuel with a valve seat protection additive. The engine does not overheat when running. Oil pressure is good. I cannot hear any pinging or knocking but engine is run without a muffler so these would only be heard at low rpm. Is it possible for symptoms to be caused by missaligning the camshaft by one tooth? Would the compression suffer if this error was made? I don't believe this is at all likely as I remember viewing the alignment mark through the large bevelled hole on the crank when reassembling but if somebody knows the symptoms of this error it would save some hair pulling on my part. Otherwise I am devoid of ideas having replaced or swapped out everything I can think of. Any suggestions out there? Cheers and thanks
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