Help with my OS .52  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> Help with my OS .52
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Help with my OS .52 - 1/23/2006 10:36:47 PM   
Zman39



Posts: 463
Joined: 1/27/2005
From: Central, FL, USA
Status: offline 		Hey All,

I have an OS .52 FS that is several years old. It ran good, but I could tell the bearings were getting bad and may have lost some of its compression so I decided to do a rebuild on it. I replaced both front and rear bearings and put a new head gasket on as well as an intake gasket. I reassembled it without problems, made sure the cam was aligned where it was suppose to be and set the valves to 2/1000". I ran about 4 tanks through pretty rich and then leaned it a little and flew it. The engine runs fine but it doesnt seem to have much compression. I can turn the prop and feel just a little bit of resistance and I go through compression. I am used to engines "popping" through compression. Is this normal for the OS 52 or should it have more compression then this?

Thanks for any help

Z
       Post #: 1

RE: Help with my OS .52 - 1/23/2006 10:44:38 PM   
w8ye



Posts: 17307
Joined: 12/11/2001
From: Taylortown, OH, USA
Status: offline 		I just rebuilt one and it will take a half gallon of fuel for the compression to return.

On a used engine like this you most probably moved the ring. It is no longer seated with the cylinder. The cylinder no longer has the ideal surface for seating a ring so it will take longer than on a new engine.

There is a possibility that you may have one of the valves too tight and you are loosing compression out the valve. You can hear this in the muffler or the carb.

There's no reason you can not just fly it and see of the compression returns?

Enjoy,

Jim

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< Message edited by w8ye -- 1/23/2006 10:50:20 PM >

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RE: Help with my OS .52 - 1/23/2006 10:50:23 PM   
Zman39



Posts: 463
Joined: 1/27/2005
From: Central, FL, USA
Status: offline 		Thanks for the reply. I was thinking (hoping) this will be the case but wanted to make sure I didnt miss something obvious. Only other thing I think I could have replaced was the sleeve but was hoping it wasnt necessary sinced it is a ringed engine. I will run some more fuel through it and see how it goes.

Z

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       Post #: 3

RE: Help with my OS .52 - 1/23/2006 10:52:25 PM   
w8ye



Posts: 17307
Joined: 12/11/2001
From: Taylortown, OH, USA
Status: offline 		It is unlikely the sleeve will ever need replaced.

You may need a ring in the future but the piston and sleeve usually last a long time.

Enjoy,

Jim

_____________________________

Attended the CutFinger Institute of DirtNap University for years but never did graduate....

Club Saito Member #7
Original AMA #31261

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RE: Help with my OS .52 - 1/23/2006 10:53:16 PM   
Zman39



Posts: 463
Joined: 1/27/2005
From: Central, FL, USA
Status: offline 		Speaking of valves. What is the ideal spacing on the valves when at room temperature?

Thanks again

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       Post #: 5

RE: Help with my OS .52 - 1/23/2006 10:54:56 PM   
w8ye



Posts: 17307
Joined: 12/11/2001
From: Taylortown, OH, USA
Status: offline 		The tolerance works out to be .0015" to .004" but .002" is fine.

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Attended the CutFinger Institute of DirtNap University for years but never did graduate....

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Original AMA #31261

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RE: Help with my OS .52 - 1/25/2006 2:55:39 AM   
philfun


 

Posts: 198
Joined: 1/3/2002
From: windsorontario, CANADA
Status: offline 		Hi Zman,

I have to reassemble an OS 48 FS.How to align the camshaft ?

Thanks

Phil


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       Post #: 7

RE: Help with my OS .52 - 1/25/2006 6:46:17 AM   
donkey doctor



Posts: 1184
Joined: 12/1/2002
From: Lake Cowichan, BC, CANADA
Status: offline 		Hello Phil; With the crank held at top dead centre, slide the camshaft into mesh with the crank gear so that the timing mark on the cam, aligns with the lifter and the push rod. It's easier to do it then to type it.

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RE: Help with my OS .52 - 1/25/2006 3:18:49 PM   
w8ye



Posts: 17307
Joined: 12/11/2001
From: Taylortown, OH, USA
Status: offline

The gear teeth are helical so the cam will twist as it goes into position. So you will need to lead the position a little when inserting so the cam will be correct when seated.

enjoy,

Jim

< Message edited by w8ye -- 1/25/2006 3:21:00 PM >

_____________________________

Attended the CutFinger Institute of DirtNap University for years but never did graduate....

Club Saito Member #7
Original AMA #31261

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RE: Help with my OS .52 - 1/26/2006 1:01:08 AM   
philfun


 

Posts: 198
Joined: 1/3/2002
From: windsorontario, CANADA
Status: offline
Thanks very much for your explanations.
Seems pretty straightforward
When I'll get a new connecting rod I'll reassemble.

Thanks again.

Phil

(in reply to w8ye)
       Post #: 10

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