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How to prep new short block when installing

Discussion in 'Mechanic and Repair' started by Roger, Aug 15, 2007.

  1. Roger

    Roger LawnSite Fanatic
    Posts: 5,923

    In a recent thread, I provided a narrative of troubles I had with my LawnBoy DuraForce engine. The result was engine failure, requiring a new short block.

    The block arrived today by UPS. We finished our mowing route early today, and were home by 5:00. So, I started the install of the new short block and hour later.

    I work outside and a platform. By 8:15 a shower arrived and I had to pack up before I was completely done. I hope to finish the project tomorrow evening.

    I was surprised at the lack of lubrication in the cylinder of the new block. The walls are dry. Since I have a day before completing the install, and still have not put the head back on, I thought I would ask about preping the walls before attempting to start the engine.

    Since the walls appear to be without any lubrication, the first few strokes after starting could be brutal. Can anybody suggest a procedure to lube the walls before starting? Or, is my concern ill-founded?

    My thought was merely to rub the walls down with engine oil before installing the head. Yes, it would probably smoke after starting to burn off the oil, but at least the walls would have some lube on the first few strokes.

    Ideas or comments? Thanks.

    P.S. I have taken some pics of the procedure to tear down and do the install. When I have a bit more time, I will post some of them, with narration, so that it may help somebody else who is considering such a project.
  2. SLR

    SLR LawnSite Gold Member
    Posts: 3,218

    I do reckon you have answered you request,with pre-oiling before assembly.
  3. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    The first few tanks of fuel should be ran in the 32 to 1 ratio. Then you can run your normal mix ratio. That's just what I do.
  4. SLR

    SLR LawnSite Gold Member
    Posts: 3,218

    Oops,forgot these were 2strokers!..eliminate my previous "pre-oil'n" cyl.
  5. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    That's exactly what you want to do using just a rub of 2 cycle oil, You never want to start a new/rebuilt engine dry.
  6. Roger

    Roger LawnSite Fanatic
    Posts: 5,923


    I finished the install this morning. The machine is back up and running. We had some heavy rain overnight, making mowing conditions difficult to start the day. So, I decided to take enough time while turf was drying out to finish.

    Thanks for the comments (restrorob, khouse) regarding preping and break-in period. I did bathe all surfaces with 2 cycle oil, and am running 32:1 fuel mix to get it started.

    All total, it took me about four hours of time. I just don't know where the time went, but I took my time, being methodical about my work. I don't do these projects every day, so had some learning to do along the way.

    Thanks for the help. Here's hoping that I'm finished with repair work on this machine for the rest of the season!! I'm not sure I have any more emotional energy to put into this simple machine.

    A few pics for now, more later when I have time to prepare.





  7. Roger

    Roger LawnSite Fanatic
    Posts: 5,923

    A few more:





  8. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023


    I'm not up on 2 cycles as I am on the 4 cycles but unless that engine has been sitting a while I'd say it was run lean. That cylinder looks awfully dry, Possibly oil mix too lean or carb leaning out a little ?

    Did you happen to check/clean the carb while it was off ?
  9. Roger

    Roger LawnSite Fanatic
    Posts: 5,923

    Restrorob, your observations are keen. Yes, I felt the same way when I opened up the cylinder cavity.

    When the problem happened, the engine was running well. Only in the last few minutes of operation was the operation degrading.

    This machine has been a major headache all season. Here are a couple of other threads that detail the problems:



    The carb was a major problem, but I felt it was finally resolved. During those carb problems, the plug color was very light, nearly white. That indicates a lean operation to me. However, when the seizure finally happened, the plug color was good, a brown-grey, perhaps a bit of red included. The color on the inside dome of the head is probably the best description.

    It is certainly possible the cylinder wall problem all started during the time of the carb problems. The damage was begun, and finally expressed itself fully at the point of seizure.

    I am sure that you, and other mechanics, chuckle (cringe ?) at my amateur style of engine repair. I'm sorry, but that is about the best I can do for my skill and training (none) level.

    Clearly, this machine would have headed to the bone yard if I had to take it to a repair shop for this work -- simply too much labor cost. Now, I am counting on another 300-400 service hours to get me through the rest of this season. This machine will not start another season as my primary hand mower.
  10. Breezmeister

    Breezmeister LawnSite Bronze Member
    Male, from South Jersey
    Posts: 1,546

    On the contrary Roger, you did a great job ! I have read with great interest
    all of your threads. In this little hole in the wall shop I now work in, I might see one or two LBs a year, always minor stuff. You have taken more time with your repair then I have ever done with LBs in the last thirty years:cry:
    Keep up the good work
    ericg likes this.

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