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Author Topic: OS LA .46 a little pinch  (Read 1328 times)

Offline Paul Taylor

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OS LA .46 a little pinch
« on: September 20, 2007, 08:23:37 PM »
A good flying buddy gave me a old used LA 46. He said it was still a good runner. Only problem is it was all taken apart and had to put it together.
After I found the correct side of the conrod, I put it all together. I did get the liner in correct. Matched the notch in the liner with the roll pin.
It has real good compression, only problem is on the down stroke there seem to be a little binding when the crank pickup passes the vent. Anyone else have one they can test.
Is this normal?

Thanks
Paul H^^
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Offline Greg L Bahrman

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Re: OS LA .46 a little pinch
« Reply #1 on: September 20, 2007, 09:05:06 PM »
I'm not sure what you mean by binding on the down stroke. In checking mine I noticed that on the down stroke it's a little harder to turn due to crankcase compression, but other than that it turns smoothly. As soon as the piston clears the ports, you can hear it and feel it when it does clear and then it turns real easy.


Quote from: rootbeard on September 20, 2007, 08:23:37 PM
A good flying buddy gave me a old used LA 46. He said it was still a good runner. Only problem is it was all taken apart and had to put it together.
After I found the correct side of the conrod, I put it all together. I did get the liner in correct. Matched the notch in the liner with the roll pin.
It has real good compression, only problem is on the down stroke there seem to be a little binding when the crank pickup passes the vent. Anyone else have one they can test.
Is this normal?

Thanks
Paul H^^
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Greg Bahrman, AMA 312522
Simi Valley, Ca.

Offline Paul Taylor

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Re: OS LA .46 a little pinch
« Reply #2 on: September 21, 2007, 06:39:56 AM »
Let me see if I can explain this a little better.

When the piston is moving up and down it is as smooth as silk. I do get a good hard turn through TDC like expected but as the pistion comes down and the top of the pistion gets level with the slot in the liner I feels like a little pinch / binding. That is also about where the fuel/air pickup in the crank just closes into the case. Maybe it is "crank case" pressure and I just never noticed it before on my other engines.
Hmmmmm.
Thanks
Paul  H^^
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Alan Hahn

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Re: OS LA .46 a little pinch
« Reply #3 on: September 21, 2007, 11:04:19 AM »
Take off the backplate and see it you still notice the problem. I wonder if you have it oriented correctly.
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Offline Paul Taylor

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Re: OS LA .46 a little pinch
« Reply #4 on: September 21, 2007, 11:13:29 AM »
Thanks Alan,
The back plate has a flat edge on the bottom and it only drops in one way. And will seat on the case.

I might try and pull the back plate off to see if I still fill the pinch. My hope is that I am feeling case pressure.

Thanks guys for the help.
Paul H^^
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Offline rustler

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Re: OS LA .46 a little pinch
« Reply #5 on: September 21, 2007, 05:12:37 PM »
It just might be a slightly twisted rod.
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Offline Greg L Bahrman

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Re: OS LA .46 a little pinch
« Reply #6 on: September 21, 2007, 06:12:40 PM »
Rootbeard
I would be just a little curious as to why the engine was all apart when you got it ? Might check with the previous owner and see if he can shed a little light on this issue. Maybe you can find out why it was taken apart in the first place. Grins
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Offline Dennis Moritz

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Re: OS LA .46 a little pinch
« Reply #7 on: September 21, 2007, 06:34:57 PM »
Since the conrod is facing the right way and backplate is oriented correctly... Any crank pin slop? Any scratches on the piston? Check for a bur on the lip of exhaust port, otherwise run it. On the East Coast of the US these engines are available used from the RC crowd. Real cheap. Great cheap stunt power. If you run the engine and the exhaust is clear, no problem. If the exhaust is black, check the muffler mounting. Keep flying for the day. If exhaust doesn't run clear then, might want to look at things more closely again. Lots of engines wear themselves true if something is slightly amiss. If the engine performs the way you like. So what. In Philly someone would leave one on your doorstep, if you needed one. Many of us have accumulated life time supplies. Do you really fly that close to the beach? Spectacular.
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Offline Paul Taylor

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Re: OS LA .46 a little pinch
« Reply #8 on: September 23, 2007, 08:40:13 PM »
OK just for the fun of it I tried to turn the back plate over. With the flat side toward the top. For some reason it did not go on the first time I tried it, but when I tried it again it went down flush. I put the screws in and no more pinch.

So my back plate was turned 180.

Smooth like it should be.

Thanks guys!
Paul  H^^
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Offline Bill Adair

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Re: OS LA .46 a little pinch
« Reply #9 on: September 24, 2007, 12:32:22 AM »
Paul,

Joined this thread late, and see that you already found the problem.  H^^

I've never owned an LA, but some of the engines I've had with that piston skirt clearance cut in the back plate, would not turn over all the way with it in the wrong position. Guess some of the LA's are an exception.

Good price on the engine, though!

Bill
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Not a flyer (age related), but still love the hobby!

Offline Leo Mehl

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Re: OS LA .46 a little pinch
« Reply #10 on: October 10, 2007, 11:08:09 AM »
Quote from: Greg L Bahrman on September 21, 2007, 06:12:40 PM
Rootbeard
I would be just a little curious as to why the engine was all apart when you got it ? Might check with the previous owner and see if he can shed a little light on this issue. Maybe you can find out why it was taken apart in the first place. Grins
Hey Greg, How did you like the magnam 53's I sold you. I think you are right about contacting the previous owner. Considering the engine was in a take apart mode there must have been some reason. Most of us modelers are quit honest about what we sell to others and if there was a problem I am sure he would tell you. Another problem coud be if you lubed it before or after you put it back together. H^^ H^^ H^^ H^^ H^^ HB~>
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