Sea King 1 HP midget won’t start

[bob-d]

Hi All, I have a Sea King 1HP midget that pops when spun over, but won’t catch
Here is what I have done:
Went through carb, lapped needle valve, set poppet height, made sure small hole under poppet open, new carb gasket, new needle valve packing. Carb meticulously cleaned. Cork float height checked, and cork covered with airplane model dope.
Good blue spark with plug grounded on motor. Even switched complete ignition plate with a running Elto Pal plate ( which has identical parts) no change. New plug,even tried bringing gap down from .025 to .020
Compression 81 pounds,(too low? maybe new rings?, but it’s a tiny piston) cylinder head gasket good, rings not stuck, no visible scoring inside of cylinder.
Took complete head assembly, and switched it over to a running Pal to rule out a bad lower bearing, which also has a new gasket, no change.
Any suggestions, bad upper bearing? How would you test? No real visible slop when you shake it back and forth. I haven’t put a dial indicator on it yet. When the ignition plate is removed, it has the usual oily look, but points and coil area are bone dry.
This one really has me baffled.
Bob D

[Doug Wilson]

sounds like could stillbesome gunk in the carb or crank shaft seals leaking 81psi should be enough for it to run ok but my money is on a fuel issue of some kind

Doug

how is it motors multiply when the garage lights get
turned off?

[kerry]

81 pounds is great for a little motor. Is the plug wet with fuel?

If you have too many, AND not enough, you're a collector.

[bob-d]

Kerry, yes it slightly wet, that’s why I tried another magneto plate. Thought I wasn’t getting a good spark, but no change with a diffent magneto plate,and flywheel (just in case the magnets were weak).

[joecb]

Will it run at all? If it will run at speed once started but is very difficult to start and will not idle the problem is likely poor crankcase compression. These very small motors are very sensitive to poor crankcase compression caused by worn crank bearings. Can you detect any lateral movement in the crank shaft (flywheel) indicating worn bearings? If bad bearings, you are looking at a machine shop project, or maybe if lucky just a much richer oil mix… like 8 to 1

Joe B

PS … how about an obstructed exhaust tube ??? Piston in backwords ???

[billw]

Just as a bench mark, I have one that ran really well, last time I tried it….which was like ’02. I remember that it ran SO much better than my MS 39 or 3/4 hp Waterwitch, that it stuck in my head. So, it IS possible for it to be a great runner……

Long live American manufacturing!

[jerry-ahrens]

I know from experience how easy it is for the tiny fuel passage in the carb to clog up. Take some carb cleaner, and using the extension tube spray through the little hole in the bottom corner of the float bowl and out through the little hole underneath the poppet valve. Follow this with compressed air to make sure it’s clean. I like to use some OMC Engine Tuner or Mercury PowerTune for this, followed by some carb cleaner.
The crankcase compression may also be a problem. With the spark plug out, move the piston up to the the firing position. Once the piston begins to move past this position, towards the carburetor, place your thumb over the plug hole and continue to rotate the flywheel slightly, as you pull your thumb away. You should hear an audible ”pop” and feel a strong vacume as you pull your thumb away. It may take a few practice tries at this but it is a good test to see if the piston is able to pull the charge in.
How much air gap will the ignition spark jump? Your spark may be weak under compression. I think this one should jump a 1/4 inch if you give it a hard pull with the spark plug removed.

[Tubs]

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

• This reply was modified 6 years, 6 months ago by Tubs.
• This reply was modified 4 years, 2 months ago by Tubs.

[bob-d]

Joe CB,it doesn’t run at all. It just pops and sounds like it trying to catch. I have tried running on 8 to 1 as well.
Jerry when I cleaned the carb, I soaked it in carb cleaner bucket overnight. I followed that up with shots of brake cleaner through all passages. After that I took nylon fishing line and ran it through the small hole under the poppet valve. I followed that up with a good shot of compressed air 80-100 psi. Before cleaning I lapped in both the needle valve, and poppet valve with Clover-leaf 1A 320 grit lapping compound.
I switched a working mag plate from a Pal, so it’s not the spark. Will try your tips for checking crankcase compression after I try Tubs mix and match parts approach onto my working Pal. Hopefully that will be able to narrow it down.
Thanks everyone for the suggestions.
Bob D

[garry-in-michigan]

Pull off the exhaust pipe and check the exhaust ports for being gummed up with carbon. Be sure the exhaust relief hole in the pipe is lined up with the hole in the casting when reassembled. Excessive back pressure can make them hard to keep running. You DID put the piston in with the deflector on the top, didn’t you?

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