Strange tuning problem

[Leebert]

Mrs Leebert's Knight Sport has been as good as gold for ages until recently. After about a month of not flying, it seemed to be running rich at the field. I had changed the fuel lines about a month or so earlier in readiness to go to Corfu (when we didn't go).

At the field, I adjusted the needle but it was still running rich at only one turn out. This didn't seem right so I cleaned out the carb and changed the fuel filter.

It flies again and is fine for Paula but it is still rich at only one turn out and I haven't had an OS 50 Hyper main needle that low/closed before.

Anyone any ideas?

I'm running 15% Rapicon and an OS No8 plug.

Thanks,
Lee

[pgkevet]

Rich in what way?
Sucking fuel faster? More vapour, staying colder than you expect, 4-stroking and lumpy? Dark plug? Was the needle tip immaculate, threads clean?

If it's giving enough power for your flying then I'd stay with a tad rich..

[Mike W]

It also depends on outside temps as well Lee .. I flew one of my knights the other week at under turn out on the main needle .. week later am back to normal at a turn and quarter .. .this is with opti 20 and mp5

[Leebert]

Rich in what way?
Sucking fuel faster? More vapour, staying colder than you expect, 4-stroking and lumpy? Dark plug? Was the needle tip immaculate, threads clean?

If it's giving enough power for your flying then I'd stay with a tad rich..

It was commented that it used fuel a bit quick when Mrs Leebert had a lesson but that was last year. It's staying stone cold but doesn't sound too bad although it 4 strokes occasionally, at least I think it does - you can hear the exhaust note change and it doesn't sound at all harsh. More kinda burbly The worst thing is it quite often dies when spooling up.
The needle tip was clean as were the threads.
I've just not had an OS at less than 1 1/4 turns. I'm half expecting it to go mega lean during a flight for some reason

[waveydavey]

Where is the bottom needle Lee? When were the bearings last changed mate

[pgkevet]

It was commented that it used fuel a bit quick when Mrs Leebert had a lesson but that was last year. It's staying stone cold but doesn't sound too bad although it 4 strokes occasionally, at least I think it does - you can hear the exhaust note change and it doesn't sound at all harsh. More kinda burbly The worst thing is it quite often dies when spooling up.
The needle tip was clean as were the threads.
I've just not had an OS at less than 1 1/4 turns. I'm half expecting it to go mega lean during a flight for some reason

Dying on spool up might be symptom of a bearing thinking about being a problem.. or rich on the low end..which in recent heat isn't that unusual. I'd ride with it a bit and up the idle if that doesn't make the clutch grab too much. Burbly on first flight can be condensation before you clear it out with some power.. burbly in average gently flight implies rich.. if ocassional then not that important unless you're trying to wring power..if always burbly after coming to temp then,yes, you're rich and should be seeing rich vibes too..

[Leebert]

It also depends on outside temps as well Lee .. I flew one of my knights the other week at under turn out on the main needle .. week later am back to normal at a turn and quarter .. .this is with opti 20 and mp5

Thanks Mike

Where is the bottom needle Lee? When were the bearings last changed mate

The screw is just below horizontal. The bearings were done about October 09. It's not done too much since then but does get run dry and treated to a squirt of after run oil.

Dying on spool up might be symptom of a bearing thinking about being a problem.. or rich on the low end..which in recent heat isn't that unusual. I'd ride with it a bit and up the idle if that doesn't make the clutch grab too much. Burbly on first flight can be condensation before you clear it out with some power.. burbly in average gently flight implies rich.. if ocassional then not that important unless you're trying to wring power..if always burbly after coming to temp then,yes, you're rich and should be seeing rich vibes too..

Idle fluctuates a bit but not too bad. Tail doesn't really wonder too much but I guess it does a bit.

Maybe I'll just lean it off a touch more so that the spool up is consistent and leave it there?

[Kwickkwack]

Hi Lee
as long as you dont do anything drastic, and adjust in small increments you should be able to do a quick hover and adjust it. As Mike says weather makes a big difference, as it cools the engine will lean off and vice versa, if it was originally set when cold, then it is likely to be to rich now
Hope you sort it OK.
Will catch up soon

[Leebert]

Thanks Rob.
Last time I set it up it was cold so that could be it. I'll slowly lean it off and see how it goes. Constantly taking a starter out to the flight line was pi*#ing me off

[Mike W]

Lee .. how old is the engine and when was the piston ring last changed ?

[Leebert]

Lee .. how old is the engine and when was the piston ring last changed ?

Not entirely sure as it was secondhand. The previous owner was Trev Burley so it had a gentle life of tail in hovering It feels like it has good compression though.

[Mike W]

I had a 50 that would be less than a turn in to produce any sort of power and always felt rich, till I realised that the ring needed changing .. new ring and it was back to normal tuning .. Or you could try using 20% fuel and see what happens

[trillian]

Just today my Ely.Q (OS50Hyper) started acting like it was running rich, coughing and smoking heavily when spooling up and a rough patch in the throttle (The OS hyper normally has a little rough patch but this was rougher than normal).

And I didn't change anything and it has been running fine. I changed the bearings a while back and it has been running great since.

I hope it's not a ring but I suppose that's a fairly cheap thing to fix if it is.