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  1. #1
    Gold Member
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    Sep 2006
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    337
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    Owego, NY
    Tractor
    PT422 w/ EH72FI engine swap

    Default PT422 engine swap completed (with pics)

    Success!

    For those of you who read my previous thread you'll know I had my previous Robin EH65 engine die on me. I will most likely fix it back up and use it for something else, but I took the opportunity to replace the original 22HP motor (that refused to start if the temperature dropped below 50 degrees) with something more powerful and hopefully better running overall. I decided to go with a 28HP Robin EH72 FI. The biggest reason for choosing this engine was that it is the same dimensions as the original so there no low risk regarding fitment.The engine was ordered from Equipatron.com and it was a very pleasant experience. I promised to post a thread with pictures of the installation, so here we go.
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    Last edited by KMA; 04-09-2011 at 11:51 PM.

  2. #2
    Gold Member
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    Sep 2006
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    337
    Location
    Owego, NY
    Tractor
    PT422 w/ EH72FI engine swap

    Default Re: PT422 engine swap completed (with pics)

    To help with removing the engine, I took off one hinge so the cover could be set behind the tractor on some buckets without having to remove the hoses and cooler. With the gas tank , muffler and heat shield removed, there is more room to work as seen in the following pics.
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  3. #3
    Gold Member
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    Sep 2006
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    337
    Location
    Owego, NY
    Tractor
    PT422 w/ EH72FI engine swap

    Default Re: PT422 engine swap completed (with pics)

    I disconnected everything, unbolted the pump and lifted the engine being careful not to catch the wiring or fuel lines on the sides of the tub. Once lifted up several inches, I propped the pump assembly up using a small bottle jack. You can see the lovejoy style coupler on the EH65's shaft. The bore on the coupler is 1 1/8" but the new shaft was 1 7/16" I chose this size shaft when ordering based on a recommended EH72 part number Terry gave me last year. Luckily, I called Terry again he told me PT custom machines a coupler in the right size. I ordered it for $40 and received it on Friday.
    Attached Thumbnails Attached Thumbnails -5-jpg   -6-jpg   -7-jpg   -8-jpg  

  4. #4
    Gold Member
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    Sep 2006
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    337
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    Owego, NY
    Tractor
    PT422 w/ EH72FI engine swap

    Default Re: PT422 engine swap completed (with pics)

    The shaft on the new engine comes much longer than necessary and needs to be cut down. Since the new coupler is them same size and shape as the old one (other than bore), I measure the old motor's shaft and cut the new one the same length. I used a metal cutting disk on my 4 1/2" grinder which worked pretty well. The key way on the new shaft shallowed out towards the end and after cutting it only about half the key stock would fit. I ground down and shaped the key stock until it fit.
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  5. #5
    Gold Member
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    Sep 2006
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    Location
    Owego, NY
    Tractor
    PT422 w/ EH72FI engine swap

    Default Re: PT422 engine swap completed (with pics)

    While I had the engine removed I did some cleaning inside the tub since it is so hard to get at when all put together. The fuel injected engine needs a return fuel line which I added to the top of the gas tank. I bought some fittings and more fuel line and plumbed it into the side of the tank such that it wouldn't interfere with the cover when lowered. I put the new engine in but did not connect it to the pump. I also had to add some oil, but the engine was ready to go otherwise. To break it in, the service manual recommends running the motor for 10 minutes at low rpms unloaded, then increase the rpms for another 10 minutes, and so on for 30 minutes total. There is t¨¨ick tick tick sound coming from fuel injector area when I turn the key on (not starting) and I didn't know if it was expected or not. I rechecked the wiring and all was good. I turned it over for about 20 seconds and it ran pretty well.
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  6. #6
    Gold Member
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    Sep 2006
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    Owego, NY
    Tractor
    PT422 w/ EH72FI engine swap

    Default Re: PT422 engine swap completed (with pics)

    I let the engine cool a while, then lifted it up again so I could mount the pump. I found it was easiest to mount the couplers and housing to the engine and angle the pump upwards (I held it temporarily with bungie cords). I slowly lowered the engine while trying to line up the splined shaft of the pump. Once the pump was attached, the block needed to be bolted to the bottom of the tub. It was tight and a little bit difficult to get at the nuts/bolts (my knuckles are pretty banged up), but it got done.

    The new engine has the oil dipstick up high causing the heat shield not to fit. I had to cut the angled top portion of the shield. I'm going to wrap the exhaust pipe in the very near future which should keep a little more heat out of the bay.

    I drove it around the yard and it definitely seemed more powerful. The engine didn't show any hesitation or struggling going up steep hills. So far so good and I'm happy with the result. I think it might get slightly better gas mileage too because of the fuel injection. I don't think it can be any worse than my EH65 was.

    Thanks for all the advice and input!
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    Last edited by KMA; 04-10-2011 at 12:02 AM.

  7. #7
    Epic Contributor MossRoad's Avatar
    Join Date
    Aug 2001
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    23,004
    Location
    South Bend, Indiana (near)
    Tractor
    Power Trac PT425 2001 Model Year

    Default Re: PT422 engine swap completed (with pics)

    Great job! Glad it worked out for you.
    MossRoad

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  8. #8
    Elite Member BobRip's Avatar
    Join Date
    Sep 2004
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    4,209
    Location
    Powhatan Va.
    Tractor
    2000 Power Trac 422

    Default Re: PT422 engine swap completed (with pics)

    Good job. Thanks for the post and pictures. When you get a chance can you post a picture of the gas tank return connection? Also the fitting you used?

    Does anyone have a concern about the shorter key and keyway?
    Bob Rip
    Tell me and I will hear.
    Show me and I will see.
    Let me do and I will learn.
    Let me fail and I will understand.

  9. #9
    Gold Member
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    Sep 2006
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    Owego, NY
    Tractor
    PT422 w/ EH72FI engine swap

    Default Re: PT422 engine swap completed (with pics)

    Quote Originally Posted by MossRoad View Post
    Great job! Glad it worked out for you.
    Thanks!

    Quote Originally Posted by BobRip View Post
    Good job. Thanks for the post and pictures. When you get a chance can you post a picture of the gas tank return connection? Also the fitting you used?

    Does anyone have a concern about the shorter key and keyway?
    There is a picture of the gas tank and return line in my 5th post above. Is that what you were looking for? Also, in the very last pic I posted you can see the return line wrapping around the back of the engine under the air filter cover. That's where is starts and then is routed along the same path as my main fuel line back to the tank.

    Regarding the key way. I was a little concerned too, so I ground down the key stock to match up with shaft as much as possible. About 2/3 of the key stock is untouched, and the back side of it tapers in an arc mimicking the key way. While grinding, I would stop and test fit over and over until it was right, and it was still over half its original thickness at its thinnest point. I'm pretty certain it will hold. Plus, the original coupler used much smaller key stock even compared to the one I modified.

    Thanks for everyone's input!

  10. #10
    Veteran Member
    Join Date
    Mar 2007
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    1,140
    Location
    Bay Area, CA
    Tractor
    Power Trac PT1445

    Default Re: PT422 engine swap completed (with pics)

    Great job! Thanks for the many pictures. It really helps understanding the details. It makes me wonder how clean my coupler is...

    Given how close the dipstick is, I think that your idea of wrapping and insulating the exhaust manifold is a great idea.

    All the best,

    Peter

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