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miller bobcat problem need help

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  • #31
    One thing I didn't mention is that. It usually bogs down during my welding usually as I'm welding and it hasn't much while grinding.
    Ill look into. The 5" grinders but I love my makita 7" that thing is a beast at removing and cutting metal.
    .
    Miller Bobcat 225NT onan
    Millermatic 211
    Spoolmate 100
    (Retapped to fit regular mig tips)
    Work better & less parts to stock.
    Miller 130xp
    T/A Dragster 85 (portability 11 pounds)
    Oxygen/Acetylene torch set 50'
    2. 4-1/2" grinders
    1. 9" grinder
    14" Makita chop saw
    1/2" Aircat impact gun 900#

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    • #32
      Engine's getting too hot, so wrong oil, wrong oil filter, toss the green foam element off the air filter, Loosing vacumn to the vacumn fuel pump is all I can come up with right now (as engine is too hot). Perhaps its time to replace the fuel pump, as thats the first thing other than the rest of the stuff I'd be doing. The engine will load up to much if the high idle no load rpm isn't enough. Its a tough one but pretty easy to solve.

      Another culprit is the spark plugs usually the left one that likes to pile.

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      • #33
        Thank you cruizer I'm checking everything you mention. Hopefully solves the problem
        .
        Miller Bobcat 225NT onan
        Millermatic 211
        Spoolmate 100
        (Retapped to fit regular mig tips)
        Work better & less parts to stock.
        Miller 130xp
        T/A Dragster 85 (portability 11 pounds)
        Oxygen/Acetylene torch set 50'
        2. 4-1/2" grinders
        1. 9" grinder
        14" Makita chop saw
        1/2" Aircat impact gun 900#

        Comment


        • #34
          what have u replaced.....

          Originally posted by eecervantes83 View Post
          One thing I didn't mention is that. It usually bogs down during my welding usually as I'm welding and it hasn't much while grinding.
          Ill look into. The 5" grinders but I love my makita 7" that thing is a beast at removing and cutting metal.
          First have you done your service to it? Service means engine oil and filter. FUEL filter, check and or replacement of air cleaned. Also replace the spark plugs. Now if that is done and you still have a probelm, after it boggs down does it restart easily, or do u have to crank, and crank? ...there are 3 possible probelms, bad oil pressure sensor(not likely as it would shut off instantly), bad/weak coil as i beleive it is, or fuel delievery probelm. If it is hard to restart, try pour a little gas in the carb, if it fires right up, you have a weak fuel pump, or a broken or leaking pickup tube. If it still does not start its a igntion coil.
          Kevin
          Lincoln ranger 305g x2
          Ln25
          Miller spectrum 625
          Miller 30a spoolgun
          Wc115a
          Lincoln 210mp
          F550 imt service truck

          Comment


          • #35
            Is it firing on both cylinders? Those Onans will run on one cylinder up to governed speed but lose it under load. They've been known to break a rod in one cylinder and keep on going.

            With it running, pull one plug wire at a time to see what happens. Use insulated pliers or welding gloves with pliers to keep from getting knocked on your can. If it keeps running with no change in speed/tone that cylinder is dead. If that's what happens, pulling the other wire after replacing the first should kill the engine.

            You could also just pull the plugs and check for compression while cranking it over.
            MM200 w/spot controller and Spoolmatic 1
            Syncrowave 180 SD
            Bobcat 225G Plus LPG/NG w/14-pin*
            *Homemade Suitcase Wire Feeder
            *HF-251D-1
            *WC-1S & Spoolmatic 1
            PakMaster 100XL
            Marquette "Star Jet" 21-110
            http://www.millerwelds.com/images/sm...rolleyes.png?2

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            • #36
              Problem solved thanks to everyone who gave advice. Bottom line the machine needed a tuneup.
              Spark plugs were shoot . And oil looked dark but ok .oil filter had some really dark oil slush . No metal in oil found. It still pops the breakers tho.
              .
              Miller Bobcat 225NT onan
              Millermatic 211
              Spoolmate 100
              (Retapped to fit regular mig tips)
              Work better & less parts to stock.
              Miller 130xp
              T/A Dragster 85 (portability 11 pounds)
              Oxygen/Acetylene torch set 50'
              2. 4-1/2" grinders
              1. 9" grinder
              14" Makita chop saw
              1/2" Aircat impact gun 900#

              Comment


              • #37
                7" draws too much power, again no rig welders that I know of uses them. Had a feeling that the problem was tuneup related, score another on for me......lol

                Comment


                • #38
                  Not yet cruizer. Still have the problem. It wants to shut off. I found a quick remedy if I pull the choke out it stays on and lets me work. But when I push the choke back in it dies. What's the deal.
                  .
                  Miller Bobcat 225NT onan
                  Millermatic 211
                  Spoolmate 100
                  (Retapped to fit regular mig tips)
                  Work better & less parts to stock.
                  Miller 130xp
                  T/A Dragster 85 (portability 11 pounds)
                  Oxygen/Acetylene torch set 50'
                  2. 4-1/2" grinders
                  1. 9" grinder
                  14" Makita chop saw
                  1/2" Aircat impact gun 900#

                  Comment


                  • #39
                    Sounds like you have a vacuum leak somewhere. Either at the intake manifold or the fuel pump (vacuum hose or pump itself, they do go bad sometimes).

                    Another thing, as you have an NT, I assume this is the old 90 degree flathead Onan. These do NOT have hydraulic lifters, they are mechanical, and need to be adjusted occasionally to compensate for wear. As Cruiser mentioned way back in this thread, if your RPM drops, voltage goes down and amperage goes up, thus tripping the breaker.

                    If you happen to remove your intake manifold to replace gaskets, take a little time to remove the covers off the valve mechanisms, and set everything back to specs.

                    I speak from experience, I've been dealing with Onans since the early 70's, when all Onans were still cast-iron blocks. Not welder power, but equipment power. Although they went to aluminum blocks in the 80's, they are still basically the same, and many of the problems are the same.
                    Obviously, I'm just a hack-artist, you shouldn't be listening to anything I say .....

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                    • #40
                      Actully quite common in the ONANS to pull the choke out slightly when running., still yes, best to adjust the tappets

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                      • #41
                        Have to completely overhaul two P218s; any reason not to upgrade them to P220 specs (slightly higher lift cam, etc)?? Also, the P218 has carb/governor linkage that is a little different from that on the P220 and P216, with the manual calling for slightly different (rpm) settings; is one type of linkage better than the other? Anything else to know about these rebuilds that isn't in the manual or part of ordinary good rebuild practice? I do know about going with new rods here, and it sounds like the headbolts ought to be replaced with good studs.
                        Last edited by old jupiter; 08-13-2014, 08:19 AM.

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                        • #42
                          I don't know of anyone that rebuilds these as the costs to rebuild generally out weighs the cost of a new engine. But good luck to you!

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                          • #43
                            We rebuilt a few of the old cast-iron blocks back in the 70's and early 80's, none of them were profitable, I suspect they would be even less profitable today with the aluminum blocks. We were lucky to get even 1/4 of the hours of new, from a rebuilt.
                            Obviously, I'm just a hack-artist, you shouldn't be listening to anything I say .....

                            Comment


                            • #44
                              you got it....

                              Originally posted by cruizer View Post
                              I don't know of anyone that rebuilds these as the costs to rebuild generally out weighs the cost of a new engine. But good luck to you!
                              Unless you have free labor, free parts, and really like drilling out bolts, buy a new one, as cruizer is right on the money, rebuilt is more than new, if u do rebuild be sure to bore.. they ware in the center of the bore.
                              Lincoln ranger 305g x2
                              Ln25
                              Miller spectrum 625
                              Miller 30a spoolgun
                              Wc115a
                              Lincoln 210mp
                              F550 imt service truck

                              Comment


                              • #45
                                Free labor, yes, and some free machining. Long ago I worked in a salt-water marina, so know something about extracting bad fasteners. And I'm the sort who just would rather build it myself than buy a crate-motor. But dang, this isn't encouraging! What were the usual early-failure points on the rebuilt engines?

                                What would you re-engine with (both Ranger 9s)?
                                Last edited by old jupiter; 08-14-2014, 09:31 AM.

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