Ack! Engine running BACKWARDS!
 

Greetings all knowledgeable ones...

I have an O.S. .40LA on my Avistar and recently it's started to run backwards when I flip start it. If I slow it down to idle, sometimes it will reverse directions and go the right way. Other times it just gurgles and stops. This didn't use to happen until about a week ago. I now have over 50 flights on it with about four gallons of fuel.

When it decides to go the right way, it runs fine. I'm flip starting it counter-clockwise which is the direction it should run.

Is this something to be concerned about? One of the guys at my field said not to worry about it as it's fairly normal with two strokers. I guess I never expected a motor could do that so I'm curious what you folks think.

Thanks for the help!

Ack! Engine running BACKWARDS!
 

Happens occasionally with my 46FX too, just kill it with a bit of throttle and re-start it.

Backward
 

SkyDude,

It does happen quite frequently.
You are lucky your engine doesn't have a reed valve.

These run both ways EQUALLY WELL...

The shaft valve and rotary valve models can only run the wrong way at low RPM. They reverse to turn normally, if you open the throttle slowly.

If they die, you can use the starter.

Sincerely,

Ack! Engine running BACKWARDS!
 

Happened to me, too, with a 46fx. Someone at the field said it was because I was priming the engine too much before starting it - i.e. turning it over too often with the carb full open before almost closing the carb and then applying the glow clip. So I now prime it less than before and it seems to be OK - the running backwards now only happens very occasionally.

Works for me!

Ack! Engine running BACKWARDS!
 

The engine kicks back when it is very primed. I hand start all my 4 stroke (but it also does it for 2 strokes) engines that way: I prime them very well, then I flip them CLOCKWISE, so when they kick back they start running the right way. Works 99% of the time.

Good luck and don't worry.

Ack! Engine running BACKWARDS!
 

Running backwards is a sign that the engine has been over-primed, as stated above. This happens with many, many, engines. Either don't prime as much, or try flipping the engine in reverse. Sometimes, though, even reverse-flipping doesn't help.

A starter may be the only solution. Just be careful not to push hard when using the starter because your engine has a bushing instead of ball bearings.

Ack! Engine running BACKWARDS!
 

Ahhhh... very good info. I have been prining it with about three or four turns with my thumb on the carb. I'll reduce it by a couple and see how that works. If that doesn't, I'll try the reverse flip.

Thanks for all the great tips.

This is such an awesome forum! How did people in this hobby do it before the internet????

Ack! Engine running BACKWARDS!
 

Like a few have said, this is caused by over priming. Hitting it with a starter is a bad idea because all that excess fuel could be thrown up into the cylinder and give a hydraulic lock. This is where hand starting is great because you soon find out exactly what the engine needs to start quickly. If it runs backwards again just pinch the fuel line and let it use up the excess.

Ack! Engine running BACKWARDS!
 

Here's another thing.... now that summer is here, and if you use a power panel glo plug driver, try reducing the heat on the glo plug. If you can avoid preignition during the start you'll have a better chance of getting things going in the right direction!