FallDownGoBoom

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Yesterday's results: about 10.3K on 15%nitro/20%oil Byron, 12x6 evolution prop, OS F plug, with the HS needle at optimum setting. We backed the needle off a bit for flight. I could try it with a 13" prop on the bench, but don't have enough prop clearance to get the plane off the ground with a 13" prop. I forgot to check idle RPM.

Numerical results aside, what's most frustrating to me is that these engines don't produce the same flight results as a 46XLS 2S. I'm flying a H9 Arrow, and the 2S gives me shorter take off runs, higher speed, and more vertical.

FallDownGoBoom

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Just in case anybody's still out there:

After tinkering with the landing gear to get enough prop clearance, I installed a 13x6 prop MAS on this engine. After fighting with the fuel feed system, we saw 10,200 at maximum power. I richened it up 1 click for flight, so probably around 10,000 rpm on the bench, and I assume more once it was airborn. The engine finally felt like it was developing a reasonable amount of thrust; it flew the Arrow with reasonable authority. Not as much speed as my 46 XLS, but it no longer felt sluggish.

Idle rpm was somewhere between 2500/3000 rpm. There's still some tuning required on the low end. But it didn't dead stick! I'd almost forgotten how to land a plane with a running engine [

W*ye, thanks for the info you've supplied... I think that's what kept me trying to get these beasts to run.

6inarow

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I am so dissapointed with these magnum 70 four strokes, It does not deadstick very often, but not reliable enough for me to fly less than 50 ft agl and no power, I have a os 46fxi that will will spank it and its a dog. I dont want to give up on it because I dont have the cash to throw around to buy another engine that could also be a pig, I am no expert so I dont know all the particulars of four strokes. The only other four stroke I have experience with is my os fs 90, Its 26 years old but is dead reliable and will hover my edge 540 nicely, I feel 100% confident to fly it inverted 2 ft off the deck and do it regularly. I love that engine and fear the day it dies. So sounds like many of you are having good a experience and maybe one of you would be willing to look at it for me if I mailed it to you, I bought the engine new in the box, but from a private sale, so hobby people will not help me with it, (unless I am willing to pay for all services) and I understand that, and that may be what I have to do. Sorry for the rambling, my 2 pennies-I think the engine itself is great, I feel you need to be an engine guru to get the most out of it.

FallDownGoBoom

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6inarow:

As a guess, you've probably got one of the 70 RFS' with weak valve springs. But I know of no way to really tell, short of sending the engine back for servicing. HobbyPeople/Global have been great to work with, at least in my case.

Fred

notruthless

Update: I ended up sending mine back to Global Hobby Services. They replaced the head, head gasket, valves, checked timing and cleaned the carb out. Their bench run tests had it at 10,400 and 2200 rpm on Powermaster 15% nitro and APC 13x6.

Once I got it back I changed to the APC 13x6, started running Cool Power 15%, and tuned the low end to suit my inverted setup. WOW! What a difference! Saw 10,300, richened and 2200+/-. It pulls like a completely different engine now. Later in the day, I ran an APC 14x4w on it and saw 9600+.

Yes, this is a strong engine, you just have to get it right!

ScottMcM

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I've got a Magnum 70 and an OS 70....the Magnum is the stronger engine......I was so impressed with the Magnum 70, that I decided to try the Magnum 91....now I have three of them

FallDownGoBoom

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Glad to hear your 70 is finally running.

w8ye

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Good numbers on the Magnum 70 now