How to remove engine from Weldanpower 250 G9?
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  1. #1
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    Jun 2018
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    How to remove engine from Weldanpower 250 G9?

    Have a Weldanpower 250 G9, with the Onan P218. Engine needs a rebuild. How is the crankshaft joined to the rotor? I don't see any set screws or splines or anything. Anyone have a service manual for it? The operators manual shows a lot of technical stuff, but not how those join

    Any ideas?

  2. #2
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    Re: How to remove engine from Weldanpower 250 G9?

    On my garden tractors with the Onan P218G there is 4 bolts that holt the drive shaft to the flywheel. I don’t know if the engine is orientred the same or if the generator is connected to the other side of the crank shaft. There should be some kind of service manuals you can look at.
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  3. #3
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    Re: How to remove engine from Weldanpower 250 G9?

    Duaneb55 gave me instruction for this. Loosen the 4 bolts connecting the generator frame to the engine and leave them threaded in a couple of turns. Remove the grillework on the control end and you'll find a long thru bolt that runs thru the gen shaft and threads into the crankshaft. The crank and gen shafts have a tapered connection. You'll need a pencil magnet to catch the two flat washers as you pull the thru bolt out. With a piece of 7/16" cold rolled long enough to contact the crankshaft and extend out far enough to hold and whack with a BFH, grind a spherical shape on the end that will contact the crankshaft. The crank has a chamfer in the threaded hole and this helps center the rod in the hole. Whack the rod like you mean it and when the gap between bolt heads and gen frame disappears they are ready to be separated.
    I have the engine manual with all info needed for overhaul and it sounds like you already have the welder manual I have. PM me your email add and i'll shoot them to you. If you get the exhaust manifold and head bolts out without twisting some off you're a lucky man!! It may help to heat the exh manifold bolt heads to red hot and let them cool before attempting removal. On reassembly coat all bolt threads with antiseize so you or the next guy can easily remove them.
    HTH,
    Mike
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  4. #4
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    Re: How to remove engine from Weldanpower 250 G9?

    You're also going to need a puller adapter to get the crank gear off. Do NOT attempt to remove it by driving a chisel between it and the block or you'll be buying a new gear.

    Name:  Onan Crankshaft Gear Puller 007.jpg
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    Name:  Onan Crankshaft Gear Puller 010.jpg
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Size:  109.8 KB

    I made this one but they can also be purchased.

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  5. #5
    Join Date
    Jun 2018
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    Re: How to remove engine from Weldanpower 250 G9?

    thanks for the info. i figured out some of that on my own before seeing this message. I ended up removing the engine with the rotor still attached. The front bearing came out of it's housing.

    I tried the steel rod, and giving it a good whack, but no dice. Now the rod is stuck inside after a few too many whacks. I was even using a pair of 1-1/8" open end wrenches and a wedge in between to put some tension on the crank shoulder and rotor, while i was doing that, and nothing.

    Assuming i don't need to do anything with the crank, i wonder if i can remove the back cover enough to get the rod bolts out without removing the rotor. Hmmm....

    I'll probably end up making a tool to go onto the crank and separate them. Kind of sucks, i was hoping to not have to make any tools. I have the machine shop capability, it just takes a lot of time. Looks like i might already have to make something for the crank gear

    Thanks for the engine manual offer, but i already found one online.

    The exhaust manifold bolts have already been helicoiled and anti-seized previously, so those came out without an issue. One head has been off . We'll see what happens on the other one.

  6. #6
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    Re: How to remove engine from Weldanpower 250 G9?

    One of the methods for removing rotors from generators (and welders) with tapered fastening is to tap a thread into the outboard end of the rotor, then insert a rod that either butts up against the end of the crank or threads into the end of the crank (preferred), then thread a bolt into the threaded end of the rotor and use the bolt as a press against the rod to pop the rotor off.

    (when I was a Generac service dealer we had a factory kit with threaded rods of the correct length to insert and push against)

    I know you have the rod stuck in there, but ..... if you can drill off the end of the push rod, maybe you can still thread the inside end of the rotor and take it apart?

    Here's a video that sorta' shows the idea :



    And here's what I mean by using a bolt inside the end of the rotor :


  7. #7
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    Jun 2018
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    Re: How to remove engine from Weldanpower 250 G9?

    Thanks for the help everybody!

    On mine, somebody already tapped the end of the rotor. However, they used such an obscure thread, i wasn't able to find anything that matched. it's definitely left-handed, and appears to be 9/16 or 14mm. Both of which seem to be unobtanium in left-hand.


    I ended up using heating and cooling on the crank snout, along with a pair of 1-1/8" open end wrenches and a wedge in between, combined with hammering on the rod going into the center of the rotor as described by mla2ofus in message #3 above.



    A helpful hint for anyone else finding this message, in the same boat, use the 7/16" rod as mla2ofus suggested! i tried a 3/8 rod, because it was all i had laying around, and that's what caused it to get stuck. The hole in the end of the crank is probably 0.370" Hammering hard on a 0.375" rod will force it into a 0.370 hole, and get it really good & stuck! Don't use a 3/8" rod

    In the end, it's apart. Thanks to everyone!

  8. #8
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    Re: How to remove engine from Weldanpower 250 G9?

    Yeah, Duane stressed to me to use 7/16" so I figured there was a good reason.
    Mike
    Ol' Stonebreaker
    "Experience is the name everyone gives to their mistakes"

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  9. #9
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    Re: How to remove engine from Weldanpower 250 G9?

    Yeah, Duane stressed to me to use 7/16" so I figured there was a good reason.
    Mike
    Ol' Stonebreaker
    "Experience is the name everyone gives to their mistakes"

    Miller 175 mig
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    Victor O/A setup
    Makita chop saw

  10. #10
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    Dec 2014
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    Wasilla, Alaska
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    Re: How to remove engine from Weldanpower 250 G9?

    This has been discussed in depth on this site IIRC, the threaded section is 5/8-11 LH Acme. They are available through tap and die houses, not your local hardware store. Some have said the threaded hole can be tapped with a 5/8-11 LH tap, never tried it. Good luck!

  11. #11
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    Re: How to remove engine from Weldanpower 250 G9?

    Quote Originally Posted by wasillashack View Post
    This has been discussed in depth on this site IIRC, the threaded section is 5/8-11 LH Acme. They are available through tap and die houses, not your local hardware store. Some have said the threaded hole can be tapped with a 5/8-11 LH tap, never tried it. Good luck!
    Huh, i wasn't able to find any discussion about it previously, which is why i started a new thread.

    Mine definitely wasn't tapped big enough to be 5/8. The bore was big enough for a 5/8 tap, but the threads weren't even close. Hopefully i'll never have to take it apart again!

    and my "local hardware store" is Mcmaster-carr. My normal experience is if it's hardware, and Mcmaster doesn't carry it, it doesn't exist!

  12. #12
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    Re: How to remove engine from Weldanpower 250 G9?

    Quote Originally Posted by wasillashack View Post
    This has been discussed in depth on this site IIRC, the threaded section is 5/8-11 LH Acme. They are available through tap and die houses, not your local hardware store. Some have said the threaded hole can be tapped with a 5/8-11 LH tap, never tried it. Good luck!
    I have to question this (above), not from a point of knowledge, but because to my mechanic's brain it doesn't "sound" right. Given that what is needed to pull the rotor is an extremely short pull at very high tension, a "fine thread" screw is going to do a much better job, with more face contact on the thread and better mechanical advantage.

    I'm curious to now where this "ACME" information comes from and I would like to learn about this.

    cheers

    EDIT :: I answered my own question, but the thread doesn't really resemble an ACME. It looks more proprietary :: http://weldingweb.com/showthread.php...m-Onan-Engines
    Last edited by John Bartley; 08-11-2018 at 08:37 AM.

  13. #13
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    Re: How to remove engine from Weldanpower 250 G9?

    McMaster Carr, although a great source of threaded fasteners, will not have a great selection of proprietary taps and dies, yes, they may have SAE, Metric, Acme and possibly Whitworth, but I have found they lack any selection of truly proprietary taps and dies. The proprietary threads I am referring to are commonly found in firearms and other mechanical devices rarely encountered by the casual mechanic. If you need some web sites for rare taps and dies, Tapco, Regal, American and Westport all sell specialty (proprietary) taps. OnanParts stated it was a left handed 5/8-11 Acme. I did some research and found LH Acme 5/8-11 Grade B7 threaded rod and appropriate nuts to make the suggested jack bolt. Since I sold the two Weldanpowers, I didn't pursue it. Good luck!
    Last edited by wasillashack; 08-13-2018 at 08:26 AM.

  14. #14
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    Re: How to remove engine from Weldanpower 250 G9?

    My two cents added, I have mid 80's Weldanpowers I use a similar setup , I had a machine shop turn me the 5/8- 11 Acme and it works fine. What can do on stubborn units is to tighten the bolt down and give it a wrap with a hammer, that should allow you to tighten a little more then repeat the wrap and tighten till it brakes free.
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