Compression Question
07-30-2008 | 11:09 AM
#1
Compression Question
I recently "resurrected" and old super tigre 51 that i had put away about 10 years ago, i probably should have left the glow plug in it, it was pretty gummed up.... It took me a while to get the engine loose, now its smooth again, but there is one difference i noticed, hardly any compression. i remember it having way more back in its days. Could leaving it in storage for that long with out oil cause the ring to lose its seal? Do you think firing it up will get it back to its original condition compression wise?
07-30-2008 | 12:15 PM
#4
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From: Castaic, CA
RE: Compression Question
I think washing the engine out with lacquer thinner will cure the problem.
I don't know why more modelers don't realize this but the best product for cleaned gummed up engine parts, not including baked on castor or heavy deposits of carbon, is lacquer thinner.
Denis
I don't know why more modelers don't realize this but the best product for cleaned gummed up engine parts, not including baked on castor or heavy deposits of carbon, is lacquer thinner.
Denis
07-30-2008 | 12:56 PM
#5
RE: Compression Question
Unless you have ugly varnish on the rest of the engine to remove, there is no need to do anything. Just add a little oil down the glow plug to lube it before your first start up. The heat and fuel will loosen the ring up and the compression should return.
07-30-2008 | 08:25 PM
#7
RE: Compression Question
i think ill try plan A and actually run or try to run the engine and take it from there. As of right now i can rotate with my index finger and not be scared of the prop biting or compression, like i used to remember it. I have to turn it over hard and fast to actually hear and feel compresion.......... The engine is not heavily used or has varnish that i can see through the exhaust port (its silver) , it probably has less than gallon through it. If that doesnt work ill have to take it apart and do plan b what djlyon said
thanks
thanks
07-30-2008 | 09:06 PM
#8
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RE: Compression Question
I'd agree, running is probably your best bet. I DO NOT like to disturb a piston/liner (disassemble) unless absolutely necessary. I just feel like the fit will never be the same - especially with ringed engines (even if you don't touch the ring). Maybe it's just paranoia, but it kinda goes along with that "if it ain't broke..." reasoning.
I just went though a similar situation with my Saito .50 - it hadn't been run in about 10 years, and compression was weaker than I remember... once I ran it though, all was well.
Do let us know how you make out with your ST...
-Joe
I just went though a similar situation with my Saito .50 - it hadn't been run in about 10 years, and compression was weaker than I remember... once I ran it though, all was well.
Do let us know how you make out with your ST...
-Joe
07-31-2008 | 05:35 PM
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From: Castaic, CA
RE: Compression Question
If running it doesn't get it done, (it probably will), you don't have to do a disassembly complete to wash the engine in lacquer thinner. Just remove the backplate and carburetor maybe the head too and slosh the engine and carburetor around in a coffee can of lacquer thinner for a couple of minutes. Spin the engine over while in the lacquer thinner to help work the thinner in the ring grove. Drain and shake the thinner out of of the engine, lube it and you are ready to go.
If Pe is correct about that engine having a dykes ring then as he says it will never feel like it has much compression when being turned over by hand. Also if it is a dykes ring gummed up oil and/or carbon between the ring and the piston can turn that ring and maybe the piston and cylinder to junk in a hurry.
Denis
If Pe is correct about that engine having a dykes ring then as he says it will never feel like it has much compression when being turned over by hand. Also if it is a dykes ring gummed up oil and/or carbon between the ring and the piston can turn that ring and maybe the piston and cylinder to junk in a hurry.
Denis
07-31-2008 | 07:27 PM
#11
RE: Compression Question
In my experience there is always a little castor behind the rings because it doesn't get easily washed out there, so even if the engine looks clean the castor behind the ring can cause it to stick. It doesn't even have to be varnished, just a gummy amber colored congealed castor can cause them to stick when cold and unused for a while.
07-31-2008 | 07:33 PM
#12
RE: Compression Question
ORIGINAL: djlyon
If running it doesn't get it done, (it probably will), you don't have to do a disassembly complete to wash the engine in lacquer thinner. Just remove the backplate and carburetor maybe the head too and slosh the engine and carburetor around in a coffee can of lacquer thinner for a couple of minutes. Spin the engine over while in the lacquer thinner to help work the thinner in the ring grove. Drain and shake the thinner out of of the engine, lube it and you are ready to go.
If Pe is correct about that engine having a dykes ring then as he says it will never feel like it has much compression when being turned over by hand. Also if it is a dykes ring gummed up oil and/or carbon between the ring and the piston can turn that ring and maybe the piston and cylinder to junk in a hurry.
Denis
If running it doesn't get it done, (it probably will), you don't have to do a disassembly complete to wash the engine in lacquer thinner. Just remove the backplate and carburetor maybe the head too and slosh the engine and carburetor around in a coffee can of lacquer thinner for a couple of minutes. Spin the engine over while in the lacquer thinner to help work the thinner in the ring grove. Drain and shake the thinner out of of the engine, lube it and you are ready to go.
If Pe is correct about that engine having a dykes ring then as he says it will never feel like it has much compression when being turned over by hand. Also if it is a dykes ring gummed up oil and/or carbon between the ring and the piston can turn that ring and maybe the piston and cylinder to junk in a hurry.
Denis
Dykes rings have a bad habit of scooping dirt and carbon in the gap between the ring and piston at the crown. If it is stuck because of that then i'm not certain that cleaning it with lacquer thinner is going to do much good. Besides if that were the case it would be a fairly well used engine.
07-31-2008 | 09:43 PM
#15
RE: Compression Question
It's back to normal!!!! Thank G. i didnt have to take it apart or order another ring. It doesn't have as much compression an my os 55ax, but enough to where i can't turn the prop with my index finger alone like earlier
thankyou
thankyou
