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Thread: M38 carburetor cleaning Tips and tricks

  1. #1

    M38 carburetor cleaning Tips and tricks

    Hello Everyone,

    The weather finally starts getting better and I have taken the m38 out for a ride and notice acceleration not constant. It was riding perfectly fine before winter stroage not sure why is this happen. I think the carburetor might need some cleaning. Can you guys give me some tips and tricks on how to do it? and what should I have done differently when storing for winter? to void this problem.


  2. #2
    Super Moderator LarrBeard's Avatar
    Join Date
    Nov 2014
    Ft. Wayne, IN
    There are additives you pour down the carburetor with the engine running that are "supposed" to clean out passages with gunk and gum - and there are fuel additives that are supposed to do the same.

    I think GMWillys and BMorgil would be the best folks to talk to that - some things are probably more damaging than helpful.

    As far as wintering over suggestions:

    A. The last tank of gas before winter should be the really good no-alcohol stuff.

    B. Treat the gas tank with a good fuel stabilizer (Sea-Foam is my choice)

    C. If you can, start it every couple of weeks and let it get good and warm. That way, any gum or gunk you missed with the precautions doesn't get a chance to set up in those
    little passages in the carburetor.

  3. #3
    Thanks for the reply LarrBeard, I did not put any fuel stabilizer before storing it for the winter last year but I did start it every other week. I will definitely do it this year. One of my friend was suggesting to put some sea-foam in the gas tank and/or some in the carburetor and let it fun for some time. What do you think is that a good idea?

  4. #4
    Super Moderator gmwillys's Avatar
    Join Date
    Aug 2017
    Modern fuel starts losing it's potency after being stored for two weeks. Ethanol fuel will corrode the aluminum components of the fuel system, and will start to give you problems. Within a couple of seasons of operation. In our area, there are a few gas stations that sell 100% gas at a premium price, for 89 octane. The few extra dollars spent, have paid for any repairs caused by the boiled corn. If you do not have 100% gas, you can purchase additives that are made as a corrosion inhibitor that is supposed to keep the ethanol from eating at your fuel system. I haven't tried it to know if it works or not.

    Seafoam works well in the tank . I don't recommend dumping anything down the carb without mettering. Hydro-locking an engine isn't a good idea, and too healthy of a gulp of cleaner can do that. You can use Seafoam in any vacuum port to clean carbon and crud from the valves, but the results depends on how long the carbon had been accumulated. The experienced guys used water to decarbon an engine, but then again it was a fine line to keep from hydro-locking.

  5. #5
    Super Moderator bmorgil's Avatar
    Join Date
    Dec 2018
    Northwestern Ohio
    If it's been setting and it got hot and cold, condensation could have gotten into the fuel. Also be sure the inside of the distributor cap didn't get a little corroded. Clean the points rotor and cap. If you started it every other week that is the best you can do. Stabilizer in the fuel never hurts when you are putting them down. It replaces the naphtha that evaporates first. I would say get some fresh fuel in her and give it a go. It will take a few miles to get the old fuel out.

    I have been involve in the long term winter storage in the Desert and in the cold, boats, trucks and cars. I can say Larry is all over it. Nothing beats starting it up once a month at least and letting it warm up. I was doing a "Military Project" once in an ocean environment. The vehicles were literally stored for years in a sea water environment. The military did two things primarily. They kept the temperature constant and they started the vehicles and ran them to temperature once a week. Second gm's point about fuels especially fuels containing alcohol, can be bad on a few things. Unfortunately Alcohol is the best way to treat water in gasoline. I have seen old gasoline that would not light with a match! Don't leave oxygenated (Alcohol) fuels in your classic for long.

    I have never used additives in my fuel or oil. I have sold and endorsed these products however. I have found that the best way to keep it clean is with quality products and clean fuel. Good products are loaded with all the additives the engineers have tested and proven effective, in labs that are space age. You can bet if there was something that gave them an edge over the competition, it would be in there. I do know those however that swear by an "additive". In the case of "water in the gas" dry gas (alcohol) works well. When you are trying to clean up inside the running engine, I don't think anything works better than a good fuel air mixture, without any additional contamination, and some heat. In other words a good hard full throttle run to heat up the combustion chamber and burn it out. In the "old days" we used to joke about taking out grandpas car and "Blowing the carbon out". Well it wasn't just a great excuse to burn rubber. It works, even if we didn't realize it! Most additives just contaminate the fuel, though some do smell good. Once combustion temperature starts to drop off a motor just gets full of junk. You want to keep the combustion temperature up to keep an engine clean. The best way to do that is to keep it in a good state of tune, the proper fuel, a good ring seal.

    After tearing down and cleaning a fair share of motors of varying conditions, I think the junk that stays inside a running motor, takes more than a "rinse" of snake oil to get out!

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