Very low compression on 40 year old 2 cycle outboard.

JackC

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This is just something to do during the fires and Covid lockdown. If I get it going I will give it to one of my daughters for their kayak or for a trolling motor.

My neighbor gave me this 1980-- 40 year old 1 HP AuqaBug outboard ( made by Tanaka of Japan) that has less than 1 hour of use 40 years ago. It looks like new. But unfortunately it was left stored in his garage rafters with fuel and 2 cycle oil in the gas tank. Gas had all dried up and left lots of gum in the carb and fuel lines. I have replaced the fuel lines, cleaned out the carb and its one small jet and had to make some new gaskets for the fuel bowl. The mag is giving great spark to the plug. BUT it only has 30 lbs compression. I believe the rings are probably gummed up and stuck but they should be like new if I can make them seal somehow..

I do not dare take it apart because parts ( gaskets and rings) are non existent. Plus I do not want to put an $ into this thing. So I look around my shop and I have CD-2 and Seafoam. I am letting seafoam sit on top of the piston now but can not do a hot soak as prescribed since I can not make it run. If that does not work I will also try some CD-2 sitting on the piston.

Any other or better ideas. Maybe some ATF or WD-40 or carb cleaner ??

IMG_0254[1].JPG
 

billr

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Please tell me that tapped hole is for the spark-plug, that the plug is dangling from its HV lead down there. Otherwise, I am horribly confused about how that engine is built! I would use Dex-type ATF. Is there any way you can spin the crank for a bit, using and electric drill coupled to the flywheel end or to the prop shaft? Have you tried to fire it at all, using starting-fluid if no joy with just the gas-oil mix?
 

JackC

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Bil: I should have said the piston movement has always been very free, just only 30 # compression. And yes tried starter fluid and I do use a drill motor to turn it over but no joy. It "may" have fired several times but not really run at all.

And, Yes the hole is where the dangling spark plug goes.
 

billr

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Does it have an actual intake (reed) valve, or just a "timed" port in a hollow crankshaft?
 

NickD

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Gather the question is, is CR 30 psi good or bad, ha, I don't know, but do know a lot of fuel air mixture has to get in when the piston is going up so can't even be close to a 4 cycle engine.

Only have one two cycle engine left in my chain saw that is about 50 years old now. Use to have a 100 HP Johnson outboard motor for Lake Michigan, but always cleaned all four spark plugs each time before going out. A Lawn Boy, two cycle, a leaf blower, and that chain saw. Never even thought about doing a compression test in these things, but feel 30 psi sounds fair.

That Johnson burnt 6 gallons per hour, memory is getting weak, three cans of Johnson two cycle oil, gas was 20 cents a gallon, non highway use and think it was around 30 cents a can or $2.10 an hour to run it. Would cost an arm and a leg to run that today.

Sure don't want to run ethanol in these things, but get some gas and two cycle oil and see how it runs.

Aviation gas was only 20 cents per gallon, got that for my boat. Plane held 42 gallons. That was $8.40 back then, today that would be 265 bucks, ain't flying anymore. And that's just the beginning.

Read back then today we will all be flying at 300 mph, try more like 3 mph and on Dan Ryan so-called expressway in Chicago, or I-94 in Milwaukee.

If you didn't have any money back then could pick up a Piper Cub for 500 bucks, same plane to day but 60 years old is like $22,000.00.
 

JackC

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Does it have an actual intake (reed) valve, or just a "timed" port in a hollow crankshaft?
Bill: This appears to be the worlds simplest 2 cycle, so assume no reed valve. Looking at the picture you can see a 1 inch pipe manifold between the carb and engineIMG_0255[1].JPG. Not much room for a reed valve setup. Looking into the pipe manifold I can see the piston going up and down, so I conclude- no reed valve.
I have spent may hours trying to research this engine, but there is almost nothing to be found.

BTW, after an overnight soak of Seafoam the compression is up to 40 from the previous 30 lbs.
 

JackC

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Gather the question is, is CR 30 psi good or bad, ha, I don't know, but do know a lot of fuel air mixture has to get in when the piston is going up so can't even be close to a 4 cycle engine.
Nick: Several tests I watched on Youtube show that new or slightly used 2 cycle engines will only reach about 85-90 psi. So I would assume anything above 80 psi should be just fine. I am now only up to 40 psi.
 

NickD

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Dropping little oil in the cylinder may show a large difference. Yours looks like an air cooled motor with the fins on the cylinder. With my old 305 CID, had to remove the prop and drop it in a 40 gallon trash can filled with water to test and tune it up.

Also see you have a can of Seafoam, just one ounce per gallon really cleans an engine up.

Motor like that would be fun on our kayak but we take it on lakes where gas engines are not permitted, but can by with an electric, but that requires a 60 pound battery, so just use paddles.
 

JackC

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I can not get more than 40 psi after adding Seafoam and ATF for several days.

I am guessing my neighbor may have run his brand new motor with only gas and no 2 cycle oil for 45 min until it stopped and ruined the rings and possibly the rod brg. Although it did not freeze up and was free even after sitting for 40 years, that is my idea. The neighbor that gave me this is not at all mechanically inclined and has had a TIA (mini stroke) so I can not confirm this. But it sounds like something he would do. He did not know about 2 cycle oil when I asked if he had any left over for me to use.

So, I think I will just sell or give it to some collector that just wants to LOOK at it and not use it.
 

billr

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If you bring it to me, I think I can get it running and will give it back to you.
 

JackC

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Bill: I do not really need it, but if you want to play with it I wiil get it to you. It would be good to see you. Anytime you are available, I certainly have nothing interesting going on. Let me know.
 
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grcauto

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Need to put it head first into a large can or tank with solvent and allow a few days to loosen it's grip on the rings. You'll need to devise a way to support it head down. I would crank it at times if you can do it. If not let it set for several days. Have everything ready to assemble. Take it out and crank it several times and install new plug and just hit it with some ether and get it started. Don't even test for compression. Even if it's low it'll likely start and the rings will seat in short order and the crude should burn off as it warms up.
 

grcauto

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BTW Maybe use fuel oil for the solvent. You could also use high grade alcohol.
 
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