This is a .70 sized 4 stroke engine that I have been using for the last 3 months. I can always easily start it by flipping the propeller backward with a chicken stick. Today, after I started it for my second flight (using the same trick), it was turning the propeller backwards. The airplane was trying to move backwards. I stopped the engine. I restarted the engine with an electric starter, and everything was back to normal. I made a couple of flights after this incidence and everything was normal.

Anyone had similar experiences? What caused this? Should I be concerned?

Thanks in advance.

Yes, they will do that sometimes. They will quit if you open the throttle a little more. Then you can try it again. I just dont bother anymore and bump it with the starter.

Good luck

Jim

Normally an engine that has been over primed will like to run backwards when hand started.

w8ye and rclier_gi,

Thank you for your input. I feel much better now.

can it hurt them to run backwards? My saito .72 did it the other day and it seemed like the compression was not as good afterwards

It probably just warmed the engine up a little.

A four-stroke engine can run reversed for a short period, if fuel has flowed-back into the muffler; or for extended periods, if the fuel-tank vent is submerged in fuel; thus allowing the muffler to behave like a 'makeshift carburettor'...

If this is the case, the engine will be able to reach pretty high RPM... the carburettor's barrel will act as an 'exhaust-throttle'...

Yeah! it happens to me always....when it starts backwards...if I advance the throttle, it speeds up and doesn't die....

It's funny to see the engine put some smoke on the carb...

I think it happens mainly because the engine is at 135 degrees, and I have to prime it to make it run...(not easy at all to start by hand) and it looses priming fast since the valves are under the engine...everything goes to the muffler....
Anyway I don't like to let it run backwards....don't want a flying 2 blade knife....