Engine swap for d902 in my bx24. Will smaller super mini's work?

[EzDuzIt]

I've been interneting hard, looking for a used d902 with in the $1500 mark and so far it's been a fruitless search. I do find smaller bore super mini series engines in my price range and wonder if that would be be a fairly easy swap and still be enough grunt to run my bx24?

Right now I got a line on a d722 for that price range which I believe is 18hp @ 3600 rpm vrs my current d902 21.6 hp @ 3200 rpm.

1st question, is this just an easy bolt up situation? Pictures look the same but??

2nd question would this power be enough for my bx24 while I take my time to rebuild my existing 902? Any problem with rpm ranges and gearing in the hst?

Im hoping you all know this, but couldn't find an existing thread on it. Any advice is greatly appreciated.

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[North Idaho Wolfman]

I'll put this in simple terms. No, don't do it.

I think you're hoping for a miracle to find a good D902 for less than about $3500.

Why don't you rebuild what you have, it will be in the range of $1500 for all new parts.

I still think with that you jumping the gun, a simple compression test will tell you if that's even needed.
You very well could just have bad injectors, glow plugs, valves out of adjustment, and all of these will cause the problems you are having.

 

[EzDuzIt]

Well Wolfman, your not making it "Ez" on me trying to avoid work.

My situation; its the middle of winter in New England, wanted to use the snow blower attachment on this new toy asap, but I guess that will have to wait. I dont have a garage, just a lean-to with open sides, so can do some putzing around under there, but will need to pull the engine to bring it to my work bench in the basement for any real rebuild work. Never done a rebuild on a diesel, only small engine gas burners.

Thought was to buy a kubota lawn tractor 3 cylinder super mini with a burnt up hst to pull used engine from since those go cheaper than engines themselves. Then do the swap in a day, bring the 902 into my basement and take my time to fix it in relative comfort. Swap back engines in the summer and sell the temporary engine on ebay to get my money back.

That was the plan... unfortunately, you keep coming around with common sense things like "do a freaking compression test" and "check valve lash" which is ruining my grand schemes. [emoji12]

Okay, lets do it your way. (Some might call it, "the right way"). My compression tester is a harbor freight for gas (300 psi). Any recommendations for a cheap diesel compression tester? Is the $30 Harbor Freight enough to get by? Also what size adapters do I need for the injectors? Are they 8mm?

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[North Idaho Wolfman]

My compression tester is a harbor freight for gas (300 psi). Any recommendations for a cheap diesel compression tester? Is the $30 Harbor Freight enough to get by? Also what size adapters do I need for the injectors? Are they 8mm?

Yep the gasoline tester won't cut it, won't go high enough.

Get the compression tester from Harbor freight for diesels.
https://www.harborfreight.com/diesel-engine-compression-tester-20-pc-62594.html
That should have the right adapter to either test via the glow plugs, or via the injectors.
Some like to use the glow plugs, less to remove to get it tested.
I personally almost always use the Injectors.

 

[EzDuzIt]

Bought the diesel compression tester, but the fittings weren't the right size. Need to get the right sized ordered.

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[EzDuzIt]

After getting the right coupler for the compression tester, I found my cylinder furthest from the fan belt is the problem. 340, 500, 520 was the max I could get from each cylinder respectively (~12 compression cycles). 220, 280, 280 was after only 3 compression cycles.

Also, the heat plug seemed much more dirty on that cylinder.

Any recommendations for my next steps?

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[EzDuzIt]

I'll put this in simple terms. No, don't do it.

I think you're hoping for a miracle to find a good D902 for less than about $3500.

I understood your simple terms of "no, don't do it" but is there any way you could give me the less simple answer?

You seem to be the most knowledgeable on this board when it comes to these engines, so I respect your input. But I do have to admit that I am very tempted to purchase a used D722 that is near by on craiglist for $1500 obo to swap the engines while rebuilding the 902. Is there some fitment issues that I am not aware of?

 

[North Idaho Wolfman]

Less simple answer is there are a lot of variables.

What was its former use?
The reason that's important is if it was a generator, or pump motor, it could be locked or regulated to be a single speed unit.

Does it have a different cooling setup that what your tractor has?

Does it have a different dimension flywheel and thus a different backing plate and different starter?

Does it have a different oil system, different pan, different filter location, different dipstick location?

Did it have any other drive option off of the motor for hydraulics or other options?

Does it have the same intake setup and or exhaust setup?

Does it have the same cooling fan, pulleys, Dyno / alternator?

Like I said, a lot of variables.

 

[motorhead]

Have you checked the valve clearances? Pull the valve cover, For the cylinder you want to check the clearance on, turn the engine by hand, in the direction of running rotation and watch the rocker arms for the designated cylinder. Turn the engine until you see the valves "switch from the exhaust valve to the intake
valve. STOP. Mark the crank pulley with chalk relative to a part of the block. NOW turn the engine ONE revolution the same direction of running rotation and line back up the chalk mark. The piston is now at Top Dead Center, ready to fire and the position you want for checking the valve clearances.
After you do that cylinder, erase the mark on the crank and repeat the steps for the other cyls.
I have had many old Mercedes diesels with tight valves that wouldn't start properly due to lack of compression.
If the valve clearance is okay on the suspected cylinder, with a pump oil can, squirt some oil through the glow plug hole and repeat the compression check. If it rises considerably, then you may have piston or piston ring issues.

 

[EzDuzIt]

Less simple answer is there are a lot of variables.



What was its former use?

The reason that's important is if it was a generator, or pump motor, it could be locked or regulated to be a single speed unit.



Does it have a different cooling setup that what your tractor has?



Does it have a different dimension flywheel and thus a different backing plate and different starter?



Does it have a different oil system, different pan, different filter location, different dipstick location?



Did it have any other drive option off of the motor for hydraulics or other options?



Does it have the same intake setup and or exhaust setup?



Does it have the same cooling fan, pulleys, Dyno / alternator?



Like I said, a lot of variables.

The engine is out of a BX1800 with a bad trans. Flywheel has no backing plate on BX since the engines are mounted backwards and pto is off the"front of the engine. I'm going to put some tape measures on both and see how it looks.

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[North Idaho Wolfman]

Post some picture of both engines.

 

[EzDuzIt]

Post some picture of both engines.

Will do, but the 280 height pixel limitation is annoying.

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[EzDuzIt]

Long story short, I bought the d722. He gave me the engine mounts too. Looks identical. Will be an adventure for all of us. Once better weather comes I'll get you all pictures.

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[North Idaho Wolfman]

Long story short, I bought the d722. He gave me the engine mounts too. Looks identical. Will be an adventure for all of us. Once better weather comes I'll get you all pictures.

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Sounds good look forward to seeing if they are the same or not, I know the D650, D750,D850, D950's are all the same externally.

 

[Gohogs]

Sounds good look forward to seeing if they are the same or not, I know the D650, D750,D850, D950's are all the same externally.

I was just wondering if the 722 worked. I have the same problem with a bx2230.

 

[lugbolt]

they had D722's with as low as 16hp and as high as 20-ish (turbo/military only)

Kubota engine website gives you some information about the sizes of the engines and their series similarities.

D722 in a BX24 is gonna be really weak. Remember there are two hydrualic systems to deal with and they both eat horsepower as long as the engine's running.

For that reason and many more I always recommend against swapping different engines as in the long term it is not worth the effort and the end result is almost always an unhappy owner. Seen it dozens of times. I remember well, guy had a G1800 and wanted a used engine rather than rebuilding what he had. So he runs out and buys a D722 which is almost identical physically as the D662 that came off. Ok great fits right on and runs fine. BUT--he also found out that generator engines are governed to 1800 rpm, and 1800 rpm is barely off "idle speed" for a G1800. So after all the work sourcing the engine and then installing it, now he's gotta take it back off again and pull the front of the motor apart to swap out the governor and cam assemblies. At this point he's back to square one--I mean it don't make no sense to buy a $1000 used engine to have to pull it half apart, I mean if you gotta pull it apart might as well pull the head and pan, inspect cylinders rods crank, repair as necessary and then reassemble so that you don't have to do the job 3 times right? But maybe I'm old school.

 

[TigerMike]

You NEVER go smaller in engine size unless you have enough money to piss away!

 

[N.W.Oregon]

Long story short, I bought the d722. He gave me the engine mounts too. Looks identical. Will be an adventure for all of us. Once better weather comes I'll get you all pictures.

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I know this thread is old, but how did it turn out?
I have a bX24 that I am looking for an engine for (Cant rebuild cause I don't have the original engine!)
Thanks for any replies!