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GMS .47

Old 09-07-2006, 06:17 PM
  #1  
jeffk464
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Default GMS .47

Getting around 12,800 on my gms .47
11x5 apc
10% cool power
Old 09-07-2006, 06:21 PM
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jeffk464
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Default RE: GMS .47

This number is on the ground, so how much rpm gain do you get when airborne. The max power of this engine is suppose to be at 16,000 rpm, so should I try running a 11x4 apc. I switched from a 11x6 to 11x5 and noticed a big performance gain, will going to an 11x4 give me even more.
Old 10-05-2006, 05:50 PM
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mjws
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Default RE: GMS .47

You don't have to rev this motor over 13K unless you're pylon racing. Your rpm numbers look fine and comparable to OS.

Only performance gain by dropping pitch is more thrust less speed. 12x4, and 12.25x3.75 are nice props on this motor for lots of thrust. Both will take the rpm down into the <12K range. With a good muffler or pipe this motor does very well. I wouldn't be going much smaller on props unless you want pure speed.

Ran mine on a pipe, 30%, and cut down pylon props and revved the piss out of it (17K or so). It was happy. Busted the carb when she got shot down and it hasn't been the same with the replacement. Beautiful, strong, easy to tune motor turned into a temperamental hard to tune POS. Retired.

Good luck. Leave the load on it unless you're racing.

Mike
Old 06-25-2007, 12:36 PM
  #4  
MOJO65-9or10
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Default RE: GMS .47

Hey there, I just got a new 47 from tower with a 20% off coupon and for 53 bucks with shipping I couldn't be happier! I first took it pretty much apart and made sure everything was clean, tight, and "SEALED". I then bench ran it with 5 or so tanks of YS 20/20 and a 12 x 4 APC and am getting about 13,400 RPM's. The bottom end needed a bunch of leaning since the manual didn't tell me were to start after I had already taken it apart but once I got it adjusted like it probably was from the factory it idles GREAT. I watch the clock in the garage while holding it at idle for 30-45 seconds and it doesn't stumble at all, just rips to full power. VERY NICE!

If you look around in the forums you can find articals about porting engines and I am not suggesting anyone try it but I like to tinker and for 53 bucks this was it. I read up on the subject and had my way with the cylinder liner. I should of tried it before but was to lazy to so I really don't know if it made any difference but it does run very well and that was suppose to be the other benifit other than some possible extra power.

To be pretty honest my other 46-50 stuff runs these RPM's so it may have in fact not done much. It was just one of those things I wanted to try for myself. Please don't ask me any more than what I stated above since I couldn't be any further from being an expert! REALLY

After my first try at a tower 46 I was real scared to try this motor but am very happy with it and can't wait to get it on a plane! With all that said my magnum 52 2-stroke still runs circles around this with the same prop and a 46ax carb on YS 20/20.

Dave
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Old 06-25-2007, 01:52 PM
  #5  
asmund
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Default RE: GMS .47

Just out of couriosity since you mentioned it, what rpms do you get on your Mag 52 on that prop?
Old 06-26-2007, 07:58 AM
  #6  
MOJO65-9or10
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Default RE: GMS .47


ORIGINAL: asmund

Just out of couriosity since you mentioned it, what rpms do you get on your Mag 52 on that prop?

Magum 52 2-stroke
YS 20/20
Mac's pipe/muffler - one piece
APC 12 x 4
14.3k rpm
It was a cooler day a couple of months back though

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