carb cleaning and sea foam

[marshall]

Just had the 50 cub out after this winter and it started right up but it's kind of sputtering up hill and conks out easily when I go from dead stop into reverse. I had to have it at FULL throttle just to make it up a gentle hill pulling an empty trailer so its really struggling. I just cleaned the main jet but that didn't help. I'm guessing theres 2 or 3 gallons of gas in there that's all old. If I buy a bottle of Seafoam how would I use it to see if I can rectify the gas and clean the carb a bit?

This loss of power has been going on for a bunch of years and I've done what I can with plugs, plug wires, distributor, coil replacements but maybe this carburetor is really the problem. Not sure how to service it beyond disassembling and cleaning with gumout which I know I've done and didn't experience much positive result from.

[Don McCombs]

There’s nothing you can add that will make bad gasoline good. Drain the old gas and start with fresh, adding Seafoam according to the directions on the can. Check for an obstruction at the outlet in the fuel tank. Check for an obstruction at the carburetor inlet screen. Is the sediment bowl clear?

[ricky racer]

I know others here have reported good results using Sea Foam but myself, I've never noticed any positive gains from using it. If you're experiencing a fuel related issue, its best to find the source of the problem and address it. Is there any restriction of fuel flow between the tank and the carburetor? If there is fix it. If not, pull the carburetor and clean all of the jets and air passages the reassemble and reinstall.
I'd suggest doing a dry/wet compression test to see what the overall health of your engine is before throwing money at it. Performing the compression test should indicate if the valves are out of adjustment causing your performance decline. That is easily remedied. If your cylinders and rings are worn, you'll be in for more work.
Once you do the compression tests, report back here with your numbers for further discussion.

[Eugene]

This loss of power has been going on for a bunch of years and I've done what I can with plugs, plug wires, distributor, coil replacements but maybe this carburetor is really the problem.

Yup. What Ricky said. Start with compression tests, dry then wet.

I suspect the engine has low compression.

[Glen]

Hi,
Here is info for doing a compression test, if you need it.
Open the throttle fully to do the compression test, so the engine can get air.
Have all 4 spark plugs out of the engine at the same time.
Charge the battery fully before the test, and use the starter.
Charge a new battery also, they are not always fully charged, a low output charger is better, 6 amps or so, that automatically goes down as the battery charges. It may take several hours to charge.
The Cub service manual says a Cub engine before Cub serial number 192113 has 107 lbs of compression, when turning at 240 RPM. That is probably for a new engine.
Some less is ok, they have said on here 90 lbs or above is ok.

The ignition points can corrode when sitting for the Winter, that can make the engine run bad, or not run any. They may need filing and cleaning. Remove all filings with a clean rag.
Check the point gap, it should be .013" for a Cub magneto.
The ignition timing is important to how the engine runs. If it is wrong, the engine can have less power than it should, or run bad.
In one of your posts from last year it shows your Cub has a magneto. I guess this is the same Cub.
I would check the ignition timing. A timing light can be used to check it when the engine is running.
I sent you a PM.

[marshall]

Ok. Thanks. I'm going to dump the gas. I'll take the carburetor off and clean it. But these have all been done before so I think those who have suggested compression are probably right. So I guess I'm in for learning a new process.

[staninlowerAL]

Follow rickey racer's suggestions and be sure that the valves are sealing. Poor sealing of the combustion chambers (cylinders) = low compression readings. JMHO Stan