Running Backwards
10-20-2008 | 09:33 PM
#1
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From: Pittsboro,
NC
Running Backwards
I have an OS 46AX that just about always starts backwards when it is cold (engine- not physical temperature). As a matter of fact, it will do this five or six times before it finally goes the right way. I am starting the engine by hand. If I use an electric starter, I don't have the problem. It doesn't backfire - I have to put my hand in front of or behind the prop to feel the wind to tell which direction it is turning. After the first flight of the day there are no more issues. What could it possibly be?
10-20-2008 | 10:59 PM
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From: Bloomington,
MN
RE: Running Backwards
Yup. It's common. Sometimes with my engines I'll just blip the throttle, and that'll get them going the right way.
Some folks will recommend flipping back against the compression as a way to avoid this. I've never been particularly good at that.
Some folks will recommend flipping back against the compression as a way to avoid this. I've never been particularly good at that.
10-20-2008 | 11:26 PM
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From: San Diego,
CA
RE: Running Backwards
Very common for the 46AX to start backwards, mine did the same thing when I was hand starting it.
I few blips on the throttle usually fixed it.
I have since invested in a starter and no longer have these problems.
I few blips on the throttle usually fixed it.
I have since invested in a starter and no longer have these problems.
10-21-2008 | 01:06 AM
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From: Warialda NSW, AUSTRALIA
RE: Running Backwards
ORIGINAL: cowboychris244
I have an OS 46AX that just about always starts backwards when it is cold (engine- not physical temperature). As a matter of fact, it will do this five or six times before it finally goes the right way. I am starting the engine by hand. If I use an electric starter, I don't have the problem. It doesn't backfire - I have to put my hand in front of or behind the prop to feel the wind to tell which direction it is turning. After the first flight of the day there are no more issues. What could it possibly be?
I have an OS 46AX that just about always starts backwards when it is cold (engine- not physical temperature). As a matter of fact, it will do this five or six times before it finally goes the right way. I am starting the engine by hand. If I use an electric starter, I don't have the problem. It doesn't backfire - I have to put my hand in front of or behind the prop to feel the wind to tell which direction it is turning. After the first flight of the day there are no more issues. What could it possibly be?
G'day Mate,
You are overpriming it, open throttle fully, prime it for 3 turns of the prop, then flick it over about 5 or 6 times, throttle back to idle, hook up glow driver, & bump against compression, don't flip it over backwards, just bump up to compression, ie, backwards & it will start the right way every time.
It helps to have the prop, so that it is horizontal, when it is just coming on to compression, that is the best way to have a prop oriented, 1) it is easier to flip start & 2) because if you have a dead stick, the prop will stop at the horizontal & won't get caught on the ground during landing.
10-21-2008 | 06:03 AM
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From: Austin,
TX
RE: Running Backwards
ORIGINAL: alan0899
G'day Mate,
You are overpriming it, open throttle fully, prime it for 3 turns of the prop, then flick it over about 5 or 6 times, throttle back to idle, hook up glow driver, & bump against compression, don't flip it over backwards, just bump up to compression, ie, backwards & it will start the right way every time.
It helps to have the prop, so that it is horizontal, when it is just coming on to compression, that is the best way to have a prop oriented, 1) it is easier to flip start & 2) because if you have a dead stick, the prop will stop at the horizontal & won't get caught on the ground during landing.
ORIGINAL: cowboychris244
I have an OS 46AX that just about always starts backwards when it is cold (engine- not physical temperature). As a matter of fact, it will do this five or six times before it finally goes the right way. I am starting the engine by hand. If I use an electric starter, I don't have the problem. It doesn't backfire - I have to put my hand in front of or behind the prop to feel the wind to tell which direction it is turning. After the first flight of the day there are no more issues. What could it possibly be?
I have an OS 46AX that just about always starts backwards when it is cold (engine- not physical temperature). As a matter of fact, it will do this five or six times before it finally goes the right way. I am starting the engine by hand. If I use an electric starter, I don't have the problem. It doesn't backfire - I have to put my hand in front of or behind the prop to feel the wind to tell which direction it is turning. After the first flight of the day there are no more issues. What could it possibly be?
G'day Mate,
You are overpriming it, open throttle fully, prime it for 3 turns of the prop, then flick it over about 5 or 6 times, throttle back to idle, hook up glow driver, & bump against compression, don't flip it over backwards, just bump up to compression, ie, backwards & it will start the right way every time.
It helps to have the prop, so that it is horizontal, when it is just coming on to compression, that is the best way to have a prop oriented, 1) it is easier to flip start & 2) because if you have a dead stick, the prop will stop at the horizontal & won't get caught on the ground during landing.
That's how I do it also. I don't even touch the prop blades, I just grab the spinner and give it a twist backwards and let the momentum take the engine into the compression stroke. That's also how I start four stroke engines.
If it does start backwards, I find that I can reverse the engine by slowly closing the idle trim until the engine almost dies, suddenly there will be a noticable increase in idle rpm, the engine just reversed itself.
10-21-2008 | 06:55 AM
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From: FrederickMD
RE: Running Backwards
As previously mentioned, backwards running is normally due to overpriming. To solve the problem when it occurs you must run the excess fuel out of the crank case. The easiest way to do this is simply pinch the fuel line shut and wait for the engine to either turn around and run the correct direction or stall. Then start it without further priming and it should run fine. If you can't access the fuel line, then you're stuck with quickly throttling up and back hoping that will turn it around.
Brad
Brad
10-21-2008 | 11:23 AM
#9
RE: Running Backwards
As previously previously mentioned 
99% of the time an engine starts backwards from overpriming. The trick of course is just to start gradually reducing the amount you prime until you hit the sweet spot. Or use the brute force method of an electric starter but then you'll never find out exactly what the engine likes. The reverse flick method is simply taking advantage of an overprime, slight as it may be.
The remaining 1% of the time is by using a power panel and overheating the plug which makes the engine fire too early.
99% of the time an engine starts backwards from overpriming. The trick of course is just to start gradually reducing the amount you prime until you hit the sweet spot. Or use the brute force method of an electric starter but then you'll never find out exactly what the engine likes. The reverse flick method is simply taking advantage of an overprime, slight as it may be. The remaining 1% of the time is by using a power panel and overheating the plug which makes the engine fire too early.
10-21-2008 | 12:19 PM
#10
RE: Running Backwards
Chris:
Using a tachometer and following the operator's manual, verify that the high and low needles have the correct settings.
Just as a test, put some drops of fuel into the carburetor nozzle before first start.
Increasing nitro content may also help.
Regards!
Using a tachometer and following the operator's manual, verify that the high and low needles have the correct settings.
Just as a test, put some drops of fuel into the carburetor nozzle before first start.
Increasing nitro content may also help.
Regards!
