Announcement

Collapse
No announcement yet.

miller bobcat problem need help

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • #46
    Onan P218, Kohler command CH20S, or Honda GX620, now, the honda was in the Ranger 8, but the output shafts are the same as the P218 & CH20S

    Comment


    • #47
      Originally posted by old jupiter View Post
      What were the usual early-failure points on the rebuilt engines?
      Bearings, piston rods, crankshafts. I always thought stock Onan parts were incapable of handling the increased power resulting from boring out the cylinders.

      If you do choose to rebuild, throw away the original oil pump, and replace with new. Even if it seems fine.
      Obviously, I'm just a hack-artist, you shouldn't be listening to anything I say .....

      Comment


      • #48
        Thank you all.

        Comment


        • #49
          oversized piston..

          [QUOTE=JSFAB;322984]Bearings, piston rods, crankshafts. I always thought stock Onan parts were incapable of handling the increased power resulting from boring out the cylinders.

          If you do choose to rebuild, throw away the original oil pump, and replace with new. Even if it seems fine.[/QUOTE

          there used to be .10 .20 and .30 pistons offered. There is no sizeable increase of power from a bored engine. The amount of increased displacement is tiny. Also many times its cheaper to sleeve the engine back to standard bore as oversized onan pistons were never cheap. The only way we ever rebuilt an onan, kohler, or honda was to turn 2 engines into one. Parts simply to expensive. We used to be able to buy stripped long block 18hp onans for 975. However that was 7-8 years ago.
          Kevin
          Lincoln ranger 305g x2
          Ln25
          Miller spectrum 625
          Miller 30a spoolgun
          Wc115a
          Lincoln 210mp
          F550 imt service truck

          Comment


          • #50
            It seems there are no more new oil pumps for these motors. Too bad. I guess it's because I was raised by two parents who suffered through the great depression and taught frugality and self-help as prime virtues, but my natural instinct is always to rebuild something old than buy anything new. My brother and sister are the same way, and any of us will spend hours working late into the evening to get something working again when others are watching the tube or whatever, and would laugh at us trying to save "old junk". Our attitude is to enjoy their laughter, but to be secretly proud (and brag about it to each other) when we can get a few more years of life out of anything from an old toaster to an old car. As Cruizer and others of us correctly point out, this will often not make business sense, might sometimes be penny-wise and pound-foolish, but we do these things on our own time and get pleasure out of it as well as any practicality.
            Last edited by old jupiter; 08-15-2014, 11:16 AM.

            Comment


            • #51
              Originally posted by old jupiter View Post
              It seems there are no more new oil pumps for these motors. Too bad. I guess it's because I was raised by two parents who suffered through the great depression and taught frugality and self-help as prime virtues, but my natural instinct is always to rebuild something old than buy anything new. My brother and sister are the same way, and any of us will spend hours working late into the evening to get something working again when others are watching the tube or whatever, and would laugh at us trying to save "old junk". Our attitude is to enjoy their laughter, but to be secretly proud (and brag about it to each other) when we can get a few more years of life out of anything from an old toaster to an old car. As Cruizer and others of us correctly point out, this will often not make business sense, might sometimes be penny-wise and pound-foolish, but we do these things on our own time and get pleasure out of it as well as any practicality.
              In the event that you decide to rebuild anyway and do not have a copy of the service manual...

              here is the link..

              http://www.cumminsonan.com/www/pdf/manuals/965-0762.pdf

              BTW...since new pumps do not seem to be available.. do not know about that particular engine or oil pump... but on many of them you can shave the end plates and or case with a milling machine to bring them back into spec and eliminate end play and pressure leakage.. from the gears wearing into them..
              Last edited by H80N; 08-15-2014, 11:43 AM.
              .

              *******************************************
              The more you know, The better you know, How little you know

              “The bitterness of poor quality remains long after the sweetness of low price is forgotten”

              Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

              My Blue Stuff:
              Dynasty 350DX Tigrunner
              Dynasty 200DX
              Millermatic 350P w/25ft Alumapro & 30A
              Millermatic 200

              TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000

              Comment


              • #52
                Originally posted by Tryagn5 View Post

                there used to be .10 .20 and .30 pistons offered. There is no sizeable increase of power from a bored engine. The amount of increased displacement is tiny. Also many times its cheaper to sleeve the engine back to standard bore as oversized onan pistons were never cheap. The only way we ever rebuilt an onan, kohler, or honda was to turn 2 engines into one. Parts simply to expensive. We used to be able to buy stripped long block 18hp onans for 975. However that was 7-8 years ago.
                Kevin
                I'm not an engineer, so I don't know. We were using these on ag equipment, driving hydraulic pumps, and there was a noticeable increase in production with the rebuilt engines. Perhaps if we had the discipline to limit the power demands, the engines would have lasted, I don't know. Possibly a rebuilt welder engine would last better, since the power produced is directly related to the amp/watt output.

                The recommendation to replace the oil pump, came directly from the dealer/service center I used to deal with.
                Obviously, I'm just a hack-artist, you shouldn't be listening to anything I say .....

                Comment


                • #53
                  Originally posted by old jupiter View Post
                  my natural instinct is always to rebuild something old than buy anything new.
                  Yeah, I fall into that trap myself sometimes. A few years ago, I spent a couple hundred dollars, and about 4 or 5 hours, replacing burners, sparkers, and grill supports and burner covers, on a propane BBQ I could have bought new for about $150 - $200 or so . Although I think the heavy-duty burner covers I made (1/4" steel) have gotten me more time out of the rebuild than I did on the original.
                  Obviously, I'm just a hack-artist, you shouldn't be listening to anything I say .....

                  Comment


                  • #54
                    Originally posted by H80N View Post
                    BTW...since new pumps do not seem to be available.. do not know about that particular engine or oil pump... but on many of them you can shave the end plates and or case with a milling machine to bring them back into spec and eliminate end play and pressure leakage.. from the gears wearing into them..
                    Yup. And another way a cheapskate like me can save certain kinds of parts (possibly tighten the meshing of the pump gear teeth) is to build the surfaces back up with a heat-cured sprayed-on moly disulfide coating, which can be good for adding .0015-.0035". I got the low-down on this from a Boeing lubrication expert in the Sixties, and took my projects to Boeing's local sub, Precision Engineering. Then an outfit called Kal-Gard began running full-page ads in Cycle magazine during the heyday of amateur 2-stroke roadracing in the Seventies and early Eighties. They sold aerosol cans or quarts of "Piston-Kote" and "Gear-Kote" (and for another crowd, "Gun-Kote"). The company was later sold, but you can now get the supplies from KG Industries. Basically you spray the moly on a carefully prepped surface with an airbrush (I have an old phonograph turntable for doing round parts), let it get dry-to-touch, and bake for an hour at 300F. When applied to piston skirts, a frequent application, the cured coating quickly gets burnished down by about half-a-thousandth, then lasts a long time. I once ran into an owner of older Brit-bikes who told me that the slides on the ridgedly-mounted Amal carbs would wear, making for lumpy idling. I molycoated a pair of his slides, and he was so happy that I became known as the local Amal carb saver for a while. Of course today if you are into hot-rodding you're aware that lots of new pistons can be had with skirts already moly-coated.
                    Last edited by old jupiter; 08-15-2014, 03:07 PM.

                    Comment

                    Working...
                    X