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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › My hyper has to much compression... Why?
11-27-2006 04:12 AM  11 years agoPost 1
50feet

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Wilmington, Delaware

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I have a 4 gallon hyper that has to much compression now. Here is the deal. I was having trouble turning over my engine. I thought it was loaded so I pulled the plug and blew out the fuel. I put the plug back in and it was hard to start. So I turned the shaft with my hand and noticed its hard and it thumps twice before it even made a complete rotation. I took of the back plate and found that the piston was not going over the top. It was pushing back.

The engine looks good inside and it had fuel lube all in it because it was running rich from when it was cold last week.It starts but its like its loaded all the time. once it fires its good and strong. Anyone have a idea why this happens?

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11-27-2006 04:24 AM  11 years agoPost 2
cdrking

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Seattle

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I took of the back plate and found that the piston was not going over the top. It was pushing back.
What does that mean, "the piston was not going over the top?"

What battery are you using to start the 50? If you're trying to use a 12 hobby battery then you won't have very good luck with them.

I've seen quite a few 50 size engines and none of them had too much compression.

Check your starter battery or try a different one.

Jeff

To hover is divine, the alternative is rather PLANE.

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11-27-2006 04:35 AM  11 years agoPost 3
50feet

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Wilmington, Delaware

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Its not the battery and starter.....
When it tune it fast with my hand the piston goes up but instead of the con rod going over the top it pops and turns back counter clock wise. If I turn it realy slow I can hear the pressure hissing around the piston and it makes a full rotation.

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11-27-2006 04:37 AM  11 years agoPost 4
50feet

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Wilmington, Delaware

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Also...
With the plug out it turns fine.

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11-27-2006 05:10 AM  11 years agoPost 5
Jafa

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Sydney, Australia

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Are you flicking the engine over?
It hits the compression and turns back?
It's hisses as you turn it manually against the compression...
That's all perfectly normal

Otherwise, turning the engine over and by hand
and the piston not going over the top does not make sense,
you would have to turn the crank backwards
to avoid going over the top


Protos | Logo 400 & 500 | Sceadu Evo | Freya Evo | Trex600N | Avant FX

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11-27-2006 05:22 AM  11 years agoPost 6
StillTryin

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Perth, Western Australia

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Maybe the hex fitting your starter wand fits into is loose and rotating on the starter shaft.

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11-27-2006 05:56 AM  11 years agoPost 7
50feet

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Wilmington, Delaware

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No...
I pulled the engine... Grabbed the fan and tried to turn it over. I am turning the fan with the back plate off with the plug in. Like any engine, the faster you try to turn it over the more pressure you get from the top compression. Well when I do it the crank starts a 6 o clock but when it gets to 12 I hear a pop and it goes back down counter clockwise. I dont know why the engine does not fire up spinning backward but it is harder to start than a 90 and I hear sqeaking from the one way.

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11-27-2006 06:05 AM  11 years agoPost 8
Jafa

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Sydney, Australia

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The sqeaking is a worry for sure

The only way for the conrod to stop at the top and go backwards
is if your crankshaft is cracked right through

Hmm, if you are looking at the engine (towards the fan)
and turn the fan/crank clockwise,
then rotate the engine around 180 degrees,
and look into the back of the engine
it will be turning counter clockwise


Protos | Logo 400 & 500 | Sceadu Evo | Freya Evo | Trex600N | Avant FX

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11-27-2006 06:30 AM  11 years agoPost 9
50feet

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Wilmington, Delaware

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right...
It does turn clock wise but the compression is so strong that it does not go over it pushes the piston back down. It was full of fuel that collects in the first chamber of my muscle pipe from running rich. The way that pipe is there is no way to drain it like a normal pipe were you can tilt the heli back and it runs out. The first chamber has a long tube in the center from the first chamber to the second chamber. Exaust will carry some out but the rest will collect and drip out for around the manifold gasket area.

I was thinking that extra fuel for me running to rich was running back in to the cylinder and causing this problem. my plug was filled to the tip with fuel and I was running the engine so that had to have happened after I shut it off. I see fuel coming out of the pressure nipple in the hose. Im going to clean it out and see if it solves the problem.

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