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HomeRC & Power✈️Aircraft🚁HelicopterEngines Plugs Mufflers Fuel › Is my engine dead? Please advise.
05-09-2013 02:49 AM  6 years ago
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cswann821

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maryland

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Is my engine dead? Please advise.
Hi everyone,

Well my question is... Is my OS-70 engine bad ? How do I know? Below is my short story of clues that I am hoping someone can advise me with whats going on with my raptor 70.

First my raptor 70 has been sitting for about 2 years with out any love, I cannot remember if I stored her making sure the engine was dry but I usually would drain and run her dry each flight in the past. I recently decided to get back into flying, and to fuel the flame by finally putting on the TT MD500 Defender body I've had sitting around for so long as well. Of course I did this MOD without checking to make sure the raptor flew fine first. It was kind of a spur of the moment thing you know!

None the less, Today I brought her out to tune the engine after knowing my hand had turned both my High and Mid needles by accident during the MD500 body install. With some new 30%cool power she started fine and sat at idle. I had opened the High and Mid needles ONE full turn from closed and to be the starting point to tweak from. With the added weight of the body I could barely get her struts off the ground even at full stick. I went and leaned her up 3 clicks and she came off the ground about 6 feet at 3/4 to full stick. Here is the issue though... With only 2 short attempts to tune, I have noticed that shortly after I get the Heli to hover, I hear a sound I would describe as "loss of power". Instead of a high speed scream the loudness drops to a lower pitch, shortly after hovering and the raptor floats back down to the ground. AT this point I also notice that she does not Idle back down to were she started...when I started her. If I try to throttle her back up from this point.... She doesn't to seem to have enouph power for lift off anymore. Unless I let her sit, stick all the way down for a minute. Then she comes off the ground to a short hover and then this whole scenario repeats. ALSO, both of the two attempts today at trying to tune the engine before the rain came in. Each time I shut the engine off to try tweaking the needles, but when I tried to restart, I found that my Brand new Enya 3's went bad/burnt out (this happened 2 times/each time I tried to hover and shut her off)...perhaps due to heat? Which brings me to another clue, the engine is also too hot to touch after these episodes, when I went to remove the glowplug, the red plastic/rubber around the glowplug-aligator clip had burn/melting marks.

Before I stopped flying, and even now.. I never mastered engine mechanics, and was hoping if any of these signs are that of a dead engine...or if I am just still to rich? ANY ADVISE OR HELP would be appreciated. If it's a dead engine how do I tell? What is a good engine now a' days? The raptor has a OS-70 right now. Might upgrade the bird to a 90 if I need to. The Thunder Tiger camo MD500 body I fit on her I believe is an extra 13lbs of weight. I know a 70 is suppose to fly her great, but If I'm going to need a new engine I might as well turn her into a 90size.

Thanks,

Chris.
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05-09-2013 03:03 AM  6 years ago
MDSCUSTOMS

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North Wales, U.K.

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Fuselage is an Extra 13 lbs of weight...?? That is an extra 6 kilos & is a seriously heavy fuselage and no wonder the Heli is struggling.

Are you sure about that weight..??

If it is correct, you seriously need to start at looking how to reduce the weight somehow or change to fuselage to a lighter one.

The weight of that Fuz together with the combined weight of the mechanics is going to be well over your original figure and I suspect a 90 engine isn't going to give you a lot more power either.

I doubt even the large petrol engined Vario Fuselages weigh as much as 13lbs.

Mark
I'm only here coz I'm not all there !!
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05-09-2013 03:17 AM  6 years ago
cswann821

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maryland

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The Manual says the "FULL equipped weight" is about 13lbs so I suspect that's with the mechanics. I haven't actually weighed it myself yet. There are plenty of videos of people flying this setup so I know it works.
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05-09-2013 03:34 AM  6 years ago
dkshema

rrMaster

Cedar Rapids, IA

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Each time I shut the engine off to try tweaking the needles, but when I tried to restart, I found that my Brand new Enya 3's went bad/burnt out (this happened 2 times/each time I tried to hover and shut her off)...perhaps due to heat? Which brings me to another clue, the engine is also too hot to touch after these episodes, when I went to remove the glowplug, the red plastic/rubber around the glowplug-aligator clip had burn/melting marks.
Can you spell "Lean"?
I had opened the High and Mid needles ONE full turn from closed and to be the starting point to tweak from.
A quick glance through the OS 70 manual clearly states that factory settings are TWO turns open for the main needle, ONE turn for the mid-range. The low speed cam needs to be set so the slot in the cam is parallel to a line running down through the centerline of the venturi. When you do that, make sure the cam pivot point is between the cam body, and the rest of the carb. Only one turn open with 30% fuel is way way way too lean. You may have done severe damage to the piston skirt, ring, and cylinder by running excessively lean, to the point where the motor repeatedly sagged, begging for mercy each time.

-----

Raptor 70? Is that an old Raptor 60 with an OS 70 in it, or a newer Raptor 90 with a 70 in it?

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has been sitting for about 2 years with out any love
Two years of just sitting does not do wonders for any of the fuel line in your system, especially that in the tank. It doesn't do too much for any seals you may have, as well. Tank stoppers, fuel filter gaskets, O-rings on needle valves or elsewhere don't stay young forever. Spend maybe three dollars on some new fuel tubing and replace all the old stuff. Then make sure your muffler is still good and tight.

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I never mastered engine mechanics
It's never too late to learn. An OS 70 (or any model 2-stroke motor) does not require a rocket scientist to tear down, inspect, and reassemble. For starters, after sitting with "no love" for two years, you could spend a few dollars and replace the front and rear bearings. Takes about an hour if you've never done it before, but after that first time, it's a snap. While you have it apart, you can look at the inside of the cylinder, looking for scratches, gouges, other forms of bad news. If it's good, it will be smooth and a bit shiny inside. The ring could be stuck in the ring groove from carbon build up, or gum and varnish from old fuel and time. A stuck ring is easily freed, a broken ring is easily replaced.

-----

13 pounds plus for a 70 is pushing it. Really pushing it. Stuffing it inside a fuselage with little cooling, or poor cooling, coupled with not really knowing how to set the needles on the carb is a recipe for disaster with any motor, even a new 90.

Before you go all out on a cool scale heli, take some time to actually learn to check your motor, fix your motor, and then how to tune the needles on your motor. But in the end, don't expect stellar performance with a 13-pound heli and a 70 motor.

You didn't mention the exhaust pipe. What are you using, and consider that a generic muffler may not be doing your motor much good.

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What is a good engine now a' days?
None, if you don't know how to properly tune it. Find experienced local help who can teach you how to set the needles without frying your motor. These days, not knowing how to set the needles on a 90 can set you back $500 or more. That's an expensive lesson.
-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz
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