OS FS120S-E compression  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> OS FS120S-E compression
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OS FS120S-E compression - 5/7/2008 1:19:35 AM   
rs670


 

Posts: 74
Joined: 7/21/2005
From: Franklin, PA, USA
Status: offline 		I purchased this OS FS120 new and have not run more than a couple gallons of fuel through it. Originnally, the compression seemed fine. Lately, even though it starts and runs good, the compression seems really low. When turning it over by hand, I can barely tell when it comes up on compression stroke. The throttle is open and valve clearance is OK. Is it possible the ring needs replaced already and is this something I can do myself with standard hand tools?
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RE: OS FS120S-E compression - 5/7/2008 1:41:57 AM   
Ken6PPC


 

Posts: 593
Joined: 6/20/2006
From: Hamilton, OH, USA
Status: offline 		I seriously doubt the ring is worn out that quickly. Try taking the glow plug out, dribbling some after run oil or automatic transmission fluid down the cylinder, and try it again. I bet your compression will come right back when it has some oil in the cylinder.

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RE: OS FS120S-E compression - 5/9/2008 3:34:49 AM   
skorman


 

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Joined: 1/12/2003
From: Virginia Beach, VA, USA
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quote:

ORIGINAL: Ken6PPC

I seriously doubt the ring is worn out that quickly. Try taking the glow plug out, dribbling some after run oil or automatic transmission fluid down the cylinder, and try it again. I bet your compression will come right back when it has some oil in the cylinder.


It sounds like the valves need to be adjusted. That can easily affect compression.


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RE: OS FS120S-E compression - 5/9/2008 3:44:43 AM   
Nathan King



Posts: 776
Joined: 5/29/2007
From: Omaha, NE, USA
Status: offline
quote:

ORIGINAL: skorman


quote:

ORIGINAL: Ken6PPC

I seriously doubt the ring is worn out that quickly. Try taking the glow plug out, dribbling some after run oil or automatic transmission fluid down the cylinder, and try it again. I bet your compression will come right back when it has some oil in the cylinder.


It sounds like the valves need to be adjusted. That can easily affect compression.



I concur. This sounds like it may be a valve problem.

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I have NO affiliation with Hobbico or any other model company. The fact that Hobbico hired a Nathan King is pure coincidence

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RE: OS FS120S-E compression - 5/9/2008 4:30:04 AM   
bigedmustafa



Posts: 2163
Joined: 6/19/2005
From: Omaha, NE, USA
Status: offline 		Nathan should know, he works for Hobbico!

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RE: OS FS120S-E compression - 5/9/2008 1:44:27 PM   
rs670


 

Posts: 74
Joined: 7/21/2005
From: Franklin, PA, USA
Status: offline 		I appreciate the replies about valve adjustment maybe causing the problem but, in my original post, I stated that there is valve clearance. If there wasn't any, I could understand compression being affected. "Too much" clearance on the other hand would affect performance but not compression. If my thinking is wrong, please straighten me out. Thanks guys.....

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RE: OS FS120S-E compression - 5/9/2008 7:08:27 PM   
Ken6PPC


 

Posts: 593
Joined: 6/20/2006
From: Hamilton, OH, USA
Status: offline 		No, you have it right. If you didn't have ANY clearance, the valves would never close completely. If you have too much clearance, you would still have compression.

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RE: OS FS120S-E compression - 5/9/2008 7:14:51 PM   
rs670


 

Posts: 74
Joined: 7/21/2005
From: Franklin, PA, USA
Status: offline 		Thanks for confirming my thoughts.... So, is there anything else to do other than replacing the ring?

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RE: OS FS120S-E compression - 5/9/2008 7:37:31 PM   
Flyer95


 

Posts: 913
Joined: 9/21/2004
From: STOCKHOLM Akersberga, SWEDEN
Status: online 		What fuel have you been running in that engine? A castor/syntetic fuel is better for glow engines!

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RE: OS FS120S-E compression - 5/9/2008 10:04:39 PM   
Ken6PPC


 

Posts: 593
Joined: 6/20/2006
From: Hamilton, OH, USA
Status: offline
quote:

ORIGINAL: rs670

Thanks for confirming my thoughts.... So, is there anything else to do other than replacing the ring?


Nothing I can think of. Strange that it would be worn out within two gallons.

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RE: OS FS120S-E compression - 5/9/2008 10:08:45 PM   
Ken6PPC


 

Posts: 593
Joined: 6/20/2006
From: Hamilton, OH, USA
Status: offline 		You might want to look at this ad:

http://www.rcuniverse.com/market/item.cfm?itemId=392991

I don't have any connection with this seller, but it seems to be priced right.

Here is Tower's price:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCT32&P=Z

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RE: OS FS120S-E compression - 5/9/2008 10:36:30 PM   
asmund


 

Posts: 1768
Joined: 11/20/2005
From: Floroe, NORWAY
Status: offline 		I had the exact same thing happen to a 30 fs that I just sold to a newcomer in our club. He suddenly had absolutely no compression even though I knew the engine was supposed to be like new, only just broken in. Problem was that I had told him to run his engine dry at the end of a flying session to avoid rust and somehow he had managed to run his engine so dry that it had absolutely no oil left in the sylinder. After I pulled the plug and squirted some fuel in it and cranked it up it was back to normal and running great.

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       Post #: 12

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