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Discussion Starter · #1 ·
I'm trying to keep my model 5124, 1977 Lawnboy (D409 engine) going as a regular use machine. I know the bottom bushing on the crankshaft is very worn and likely contributes to low crankcase vacuum and lower seal wear. Ideally, I would like to source a NOS crankcase assembly. At this point in time, is this too much to hope for? Alternatively, I understand that boring out the lower bushing and replacing it with a bearing is maybe a possibility. I'm not sure what level of machine shop expertise this would require?

Any thoughts or suggestions you may have are welcome.
Thank you.
Grant
 

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I'm afraid I won't be of much help but just wanted to drop a note to say welcome to the forum Grant! :)

One of our LawnBoy aficionados should be along shortly. ;)
 

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Hello, Grant, and welcome to the forum. Yes, replacing the lower bushing with a bearing is a great way to upgrade your machine. There was just such an article posted on our sister site that you may want to check out. The task is above the average homeowner expertise but pretty simple for a machine shop. Check out the article in the Walkbehind section of:

mytractorforum.com

I think you'll be pretty impressed with the article and the results!
 

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Discussion Starter · #4 ·
Thank you very much for the welcome and the helpful information.

I was also wondering if there is some reference information available that outlines what the differences are between the various D400 models, i.e., D400, D409, D415, D433, etc. I would like to know if the basic parts such as cylinder jugs, crankshafts and crankcase blocks are interchangeable.

Grant
 

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Thank you very much for the welcome and the helpful information.

I was also wondering if there is some reference information available that outlines what the differences are between the various D400 models, i.e., D400, D409, D415, D433, etc. I would like to know if the basic parts such as cylinder jugs, crankshafts and crankcase blocks are interchangeable.

Grant
Go to LawnBoy's website & then go to the parts lookup & type your model number in. When you get to your parts IPL page, look for the "Manuals" button (in the middle on the left side) to select the repair manuals. There is an excellent group of engine reference charts towards the bottom of the repair manuals. I think that 7/8"x1"x1" bushing is #703207, but they don't give it a part number on the IPLs. I have yet tried to replace one. You could make your own removal punch tool if you have access to a lathe. Heat the crankcase up to 350°F degrees for 20 minutes first.

You will still have to drill the two oiler holes through one side & chamfer the top edge for a thrust surface. The above mentioned 1" wide INA 1416 needle bearing installation won't allow oil to properly circulate through it like the bushing, nor does it provide a proper thrust surface for the crank journal to rest on...
 
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