os 70 szh heli engine impossible to tune
10-29-2004, 07:24 PM
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os 70 szh heli engine impossible to tune
Hello all experts I need help,
I have a brand new 0s 70 szh heli engine on my raptor 60.When I first ran it with needles at H- 2 turns out, M- 1 turn out, L- centered it was horribly rich and would not spool up at all.I leaned it at the high needle to 1.5 turns out.The bottom was still too rich, but the top would clean up enough to hover(still very rich).My second tank it would die evey 5 min. or less. I leaned the mid 3 clicks in.It still dies.To make a long story short I have went as far as H-1 turn, M-.5 turns to 3.5 turns, L-slightly rich or lean.I have replaced all fuel lines, cleaned the carb twice, pouring alcohol in the feed holes to make sure there no trash.The back plate is always cool to touch.Changed the glow plug.It seems to die only in the mid range either trying to hover, or if I get to the upper range and back off the throttle some to lose altitude.At hover throttle it runs like crap.I have run out of ideas on this and will smash it,Please help save the life of my os 70.
I have a brand new 0s 70 szh heli engine on my raptor 60.When I first ran it with needles at H- 2 turns out, M- 1 turn out, L- centered it was horribly rich and would not spool up at all.I leaned it at the high needle to 1.5 turns out.The bottom was still too rich, but the top would clean up enough to hover(still very rich).My second tank it would die evey 5 min. or less. I leaned the mid 3 clicks in.It still dies.To make a long story short I have went as far as H-1 turn, M-.5 turns to 3.5 turns, L-slightly rich or lean.I have replaced all fuel lines, cleaned the carb twice, pouring alcohol in the feed holes to make sure there no trash.The back plate is always cool to touch.Changed the glow plug.It seems to die only in the mid range either trying to hover, or if I get to the upper range and back off the throttle some to lose altitude.At hover throttle it runs like crap.I have run out of ideas on this and will smash it,Please help save the life of my os 70.
11-01-2004, 12:43 PM
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RE: os 70 szh heli engine impossible to tune
First off, how was your engine broken-in? On a test stand? In the heli? It does make a very large difference. Model engines break in best when run at full throttle. Ringed engines need to be run extremely rich for the first 15 minutes or so and then gradually worked towards peak RPM with a rich-lean-rich lean method.
What exhaust system are you using? Is it suitable for the engine? If it's a tuned-exhaust system, have you made sure it's properly tuned? Tuned systems are most definitely "bolt-on and go". You have to tune them for a specific RPM range, usually at full throttle. This makes them large mufflers once you're off full throttle, and then they'll trend very rich.
To check an engine, you should put it on a test stand with a propeller that will allow it to turn in the RPM range it will fly at. Then you can get everything properly set up. Many heli tuning problems arise from the fuel system being affected by vibration, from an exhaust system that doesn't really suit the engine, from trying to set the engine to the same settings others do, from over-reliance on temperature, and from the difficulty of getting a good breakin when the engine's in the heli. Any of these could be the problem source.
An engine should be well broken-in before it goes into the heli. That way, you know what to expect. A new engine in a heli needs full-throttle running at a very rich setting, and that means you'll have idle problems...if you can't auto to landing, then you'll have problems. Breaking-in an engine in hover doesn't work so well because the engine isn't running at full bore, and won't be developing full operating temperatures.
What exhaust system are you using? Is it suitable for the engine? If it's a tuned-exhaust system, have you made sure it's properly tuned? Tuned systems are most definitely "bolt-on and go". You have to tune them for a specific RPM range, usually at full throttle. This makes them large mufflers once you're off full throttle, and then they'll trend very rich.
To check an engine, you should put it on a test stand with a propeller that will allow it to turn in the RPM range it will fly at. Then you can get everything properly set up. Many heli tuning problems arise from the fuel system being affected by vibration, from an exhaust system that doesn't really suit the engine, from trying to set the engine to the same settings others do, from over-reliance on temperature, and from the difficulty of getting a good breakin when the engine's in the heli. Any of these could be the problem source.
An engine should be well broken-in before it goes into the heli. That way, you know what to expect. A new engine in a heli needs full-throttle running at a very rich setting, and that means you'll have idle problems...if you can't auto to landing, then you'll have problems. Breaking-in an engine in hover doesn't work so well because the engine isn't running at full bore, and won't be developing full operating temperatures.
