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Need Help with Antique Tecumseh, Long

Discussion in 'Mechanic and Repair' started by MBDiagMan, Oct 9, 2012.

  1. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Messages: 852

    I haven't been on this forum in a long time, but I remember the great amount of small engine savvy on here so I would like to ask for help. Although I am working on a Tecumseh OH160, many of my questions are more related to general small engine knowledge as opposed to model specific information.

    I am trying to fix up a Miller BlueStar welder that's probably a little over 20 years old. It came with a Tecumseh OH160, but the owner had someone put a different OH 160 on it after the first one trashed. The reason I point this out is that I have very little history and suspect that the correct carburetor might not be installed, or other parts mismatches.

    It has sat for probably about a year, and evidently outside for part of that time although it was inside when I picked it up.

    Owner complaint:

    He said the engine would not make enough power to weld with and that the engine was smoking badly. He had gotten governor instructions and tried to speed it up so he could weld with it so the governor will need to be sorted out after I get the engine running correctly.

    Note that I realize that there can be electrical problems causing it not to weld and I am capable of dealing with that part of it when I get that far along with the project.

    Initial Examination:

    When I brought it to my shop and looked it over, I found oil in the crankcase that looked like grey paint. I managed to start the engine and run it and it indeed is basically a "mosquito sprayer." The smoke looks white under the Metal Halide lights in my shop, but I believe it is actually blue. I left it in the bed of my pickup for now and it soaked the side of the pick up bed with oil from the exhaust while running.

    Although I have yet to load the engine, it sounded and ran pretty well. When I pulled the spark plug it looked oily, but not oil fouled as I expected it would be. In fact what looked like oil might have been gas instead.

    When I pulled the plug to drain the oil, a few tablespoons or so of water came out before the grey paint looking oil. I let it drain overnight and filled it with some Delo thinking that the extra detergents in this type oil might help to clean it out. The new oil turned grey right away.

    I removed the oil breather connector on the valve cover and it was pulsing pressure out of the valve cover vent. It did not seem to make any difference in how much oil it was blowing.

    Further Examination:

    When I changed the oil I pulled the plug and put some Marvel Mystery Oil in the cylinder thinking there is a small possibility that the rings are stuck. After it setting overnight, I turned it over to blow out the MMO and put the spark plug back in. I started it up and ran it for awhile. Once it warmed up it mysteriously started losing speed and died. With the ignition parts being rare and expensive, I was worried about that, so I sprayed a little carb cleaner in the carb and it would bust off and run a little proving the igniton okay. There was fuel in the fuel bowl and plenty at the fuel line where it enters the fuel bowl.

    I left it and ran some errands. After coming back to it being cooled off, it started and ran fine, making me think that it had possibly been trying to sieze up although when it wouldn't run before, the starter would spin it over easily.

    After pulling the plug and soaking the piston overnight with MMO again, I spun it over to blow out the MMO and put a compression gauge on. It made 95PSI compression while spinning it over with the starter.

    I then replaced the spark plug and ran it some more before doing what I thought would be a dry compression test. It then made 115PSI compression. I thought this was puzzling. I expected the dry test to give a lower number. Also, with it blowing smoke I didn't expect it to make this much compression in any situation thinking 1.) it's probably worn out and 2.) this engine has a compression release to make it easier to start.

    After pulling the compression gauge the last time, I looked in the cylinder and could see liquid on top of the piston. I turned it by hand and the liquid remained. I then turned it with the starter to blow it out and ran the piston to the top where it looked pretty dry. I then walked away to let the cylinder dry out as much as possible so I can check compression again tonight.


    It seemed like the liquid on top of the piston, in the last paragraph above, was gasoline. Is this possible? Could there be so much gasoline in the cylinder that it would stand there as liquid? Could it be running this ridiculously rich and not blow BLACK smoke?

    I assumed from the beginning that I would have to take it apart and see to the rings and maybe even bore it and replace the piston. With this kind of compression, could it still be blowing that much oil past the rings?

    Since I have no history on what has been done and what parts were used, I suspect that this is not the correct carb for this engine. In the Tecumseh manual it shows several ones and most of them have an adjustable main jet, while this one does not. It is fixed. I am curious if it could be so rich so as to be causing the smoke and the liquid on the piston?

    I don't mind taking it apart and putting in rings, or boring it or whatever needs to be done, but I don't want to do this only to get it back together and find that I still have a carburetor problem or some other ill that is causing the smoke and reported lack of power.

    Thanks very much for your thoughts. If I do get to the disassembly stage I will be asking some questions specific to this particular animal.
  2. dboyd351

    dboyd351 LawnSite Bronze Member
    Messages: 1,124

    I'm not familiar with this engine. Is it by any chance water cooled? The reason I ask is the "oil" looking like grey paint sounds exactly like you have a substantial amount of water mixed in the oil. The statement that a few tablespoons of water came out before the grey colored oil, also sounds like water in the crankcase.
    Sounds like you have water in your oil and you need to find out where it is coming from before you do anything else.
  3. BigFish

    BigFish LawnSite Platinum Member
    Messages: 4,157

  4. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Messages: 852

    Thanks for the great information and links.

    I managed to finish a wet/dry compression test last night. I got 110 PSI dry and 120 after putting a little oil in the cylinder. I think it's coming down to cleaning the crankcase of the "grey paint" while I have it apart for overhaul.
  5. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,335

    That "grey paint" acts like a fine valve grinding compound...
    Doubt you have any crosshatches in the cylinders...bearing surfaces probably are dull...
    Posted via Mobile Device
  6. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Messages: 852

    Thanks Piston Slapper!

    Evidently the grey paint did not happen until the owner put it away without running it. I have run it very little, so hopefully no significant damage has been done. I think I will need to put some solvent in my parts washer for this job.
  7. JimQ

    JimQ LawnSite Bronze Member
    Messages: 1,139

    Posted via Mobile Device
  8. JimQ

    JimQ LawnSite Bronze Member
    Messages: 1,139

    I rebuilt an OH160 for a customer with an old skid steer last winter It was also smoking like crazy. The source of the smoke was extremely worn vavle guides. Pull your muffler off and look inside. I would bet you wil find that the stem and back of the vavle are covered in oil and buildup. Parts are getting expensive and tough to find for these things. Looking back at that invoice, I see that the exhaust valve 730218 alone was about $80. Another $20 for the guide kit. I also remember it being kind of a PIA to get the valves out.

    Posted via Mobile Device
  9. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Messages: 852

    Thanks Jim!

    In reading through various material I have seen mention of replacing the valve guides and have also seen mention of using valves with 1/32" oversize stems and then reaming the guides to fit. In your description it sounds as if the valves and guides BOTH were severely worn.

    It sounds like it might be worth pulling the head and examining the guides before going ahead and taking the whole engine apart. The head will have to come off any way.

    Thanks again.
  10. JimQ

    JimQ LawnSite Bronze Member
    Messages: 1,139

    If memory serves me, the valves with oversized stems were NLA. Yes, the valve stems were also worn. I remember needing to get creative to compress the valve springs and get the keepers out. Replacing the guides wasn't too bad. I slowly heated the head with a rosebud and used a press to pop them out. The recommend method calls for immersion in hot oil. That sounded like a PIA to me. Probably safer but...

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