I just bought a p-51 mustang giant scale 84in ws with a g4500 in it. I just took it out to taxi in the driveway, when i started it the Engine ran backwards on 2 separate occasions? Why is this? Also Im in a very cold climate, Maine, I can only seem to start it just after i take it outside...is it too cold to run now..or what?

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Yea mine goes backwards once in a while too. I only get that when using a chicken stick cuz if you dont follow through the whole cycle...I dunno how to explain it...like flip it through the the top dead center. If you dont follow through the pressure might fire the piston back down before it reaches top dead center and will start backward. Well if you cant follow it through cuz its kinda hard sometimes. I never tried this myself cuz I just reach for the electric starter but... if it goes backwards when you flip forward then try fliping backwards, maybe it will go forward

A lot of times when an engine is over primed, it will run backwards. You should be able to spin or snap the spinner backwards and start the engine. It bounces on compression going backwards, fires and starts forward. I start nearly every engine this way.

On an engine that big, never pull the prop through compression like you do a .40. If it backfires it has enough power to break fingers. A buddy of mine broke his on a Moki 1.8 like this.

Put the prop up against compression like you were going to start normally, but twirl the spinner backwards. It should start in a couple of tries.

The back flip method is the best. Still sometimes my 3250 will double kick and start backwards. It dosn't hurt any thing just kill it and try again. Maybe by describing how I back flip will help you a little. First a good choke is needed.Usually three flips with my thumb over the carb and wide open throttle. Then three flips wide open without the thumb.(my prop in on compression when it's horizontal)
Then attach the hot shot. I am on the front side to toward the right wing so I can use my right hand. I put my thumb on the spinner and my middle finger on the top front edge of the prop. Then it's kind of like snapping your fingers. The thumb gives you leverage and the middle finger pushes the prop against the compression. It works every time. And if it kicks back your middle finger is just pushed back. Give it a try.

david

I use the backflip method exclusively with large engines, most start with a single backward flip with the Davis Jumbo chicken stick after priming. I do like Ed and run them forward against compression and then a smart backward flip.

I back flip the ST2300 and larger. They usually start forward, but if they don't, I get it running at the slowest idle that it can and feather the throttle. In a few seconds the engine comes to life and running the way it should.