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about ready to pull my hair out!!

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  • about ready to pull my hair out!!

    ok, I bought a miller bobcat 225g with a onan p216g. I had always wondered why it puked out oil out of the fuel pump. needless to say i found out what was causing it. I found that I had 2 bent intake valves and lost the seat in on of them and as of right now the engine is FUBAR'D as of right now. So here is the million dollar question of the day... The welder is a 1991 model according to MILLER, so I am guessing the engine is a 1990-1992.. I found another p216g with very little run time, but before i do that i was wondering if these engines will swap out or if I am going to run in to problems with the crank mating to the generator...
    Last edited by ethandg; 01-31-2014, 06:19 PM.

  • #2
    Don't take my word on this but check it out

    I believe that engines that are designated for use with generators usually have tapered shafts whereas other engines use straight shafts. See which yours has and limit your search to them. Also, and once again this is just my understanding so you'll have to check it out yourself, but I think the mounting holes and bolt patterns are more or less universal for various sized engine platforms and generators, so you may not even have to limit yourself to the original brand and model of engine if you are getting one of about the same horsepower.

    And with that said I wish you all the luck in the world finding a 20+ year old used engine in good repair.


    • #3
      called cummin/onan

      I found out today that for that engine there was 11 different crankshafts, I don't know if they are generational or by application. But I guess the only way I am going to find out is to get the full numbers off of both engines and run them to see if they are interchangeable. And you do bring up some good points as far as mounting. I have heard that some later model p216 in a miller application were threaded.


      • #4
        Maybe change the title in your thread to reflect your question. Something like Onan P216g interchangeability.
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        • #5
          Thread title

          Noted sir!!! Didn't even think of that!


          • #6
            Old engine has a code on the data plate, the new engine must have the same code


            • #7
              data plate

              So the data plate on the engine has to match character for character?? So if that is correct I need to find a 20+ year old engine with low hours? Or drop about 1500.00 on a new engine?

              I wouldn't think there would be THAT much variance in crankshafts, with the exception of narrow taper, wide taper and threaded.


              • #8
                Lots of variations, thats why the engines have a specific code


                • #9
                  Have you looked into the cost of overhauling your engine?
                  New valves, guides, springs, cam shaft etc.
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                  • #10

                    Cruizer, I found that out when I called Cummins/Onan, lol. I could not believe how many variations there were!!! But I reckon all I can do is get the numbers and run them.

                    Snoeproe, I was told by my mechanic that between machining and rebuilding it I would be money ahead to just buy a new one, because the valve seats would have to be oversized among other things. He also said that if I could find a used one that wasn't wore out that may be my best bet. I don't have a lot of money to blow on a engine and, I found one that would be pretty much just given to me. But it has to be the correct variation of that engine. It is on a small Case lawn tractor.


                    • #11
                      At that price (almost given to me)can you swap the top end?---Meltedmetal


                      • #12
                        Thats true, as jugs pull off, why not r/r the jug, piston and head. Way simpler than pulling and replacing the engine, as long as the connecting rod is ok.

                        Then you could use ANY P216 engine as a donor.
                        Last edited by cruizer; 02-01-2014, 01:24 PM.


                        • #13
                          Going to guess and say that the previous owner, used moisture ridden dinosuar oil, in which moisture got into the hydraulic lifters, froze, and the lifters became solid, driving the valve/s down enough to make contact with the piston. This usually just bends the pushrods but can take out a valve pretty fast too. So your going too have to replace them from the donor.


                          • #14
                            swapping guts

                            From what I have seen the block casting is one piece, so if any guts swapping were to be done it would have to be the bottom end, crank, rods, and pistons. But I would be curious to how much machine work would run??


                            • #15
                              No detachable jugs on the Onan, no hydraulic lifters, flat head design so no chance of the valves hitting the pistons.

                              Actually, Onan had at least 23 different cranks over the years. All the tapered cranks for Millers were a 1.50 taper (1.5"/foot) with the most common being the type "45BH". Miller changed to the type 45EE, 1" threaded crank in the mid 90's.

                              The rare "45CB" and "45CE" cranks were also a 1.50 taper with slightly different length details and 7/16-14 center bolt threads rather than the 5/16-24 of the common 45BH cranks.

                              My recommendation would be to:
                              1) Overhaul the one you've got with new pistons, rings, valves, guides, etc.
                     (or individual parts as needed)
                              I believe TJ ( offers oversized seats that would require the services of a machine shop to install.

                              2) Get the one that would pretty much be given to you and swap out the cranks. However, this requires tearing both units down completely at which time you can assess exactly what parts (rings, gaskets, etc.) that you'll need to put it back together. I've taken this path when swapping an earlier tapered crank out for the later threaded version.

                              Either way, due to design, you'll have to pull the pistons to get the crank out so plan on rings for hard parts at the very least.
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