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Discussion Starter #1 (Edited)
I have acquired this tractor. Upon getting it home I started to tinker with it. I cleaned the carb added a new battery and it started and runs good. Everything works as it should. My problem is it is smoking, it is a blueish whiteish smoke. It is worse at idle and pretty much clears up at wot. The tractor had been sitting a long time before I got it. I’m not sure where to start on diagnosing it.

I have a decent understanding how things work. I was thinking compression test. How would I check for a bad head gasket?




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I have acquired this tractor. Upon getting it home I started to tinker with it. I cleaned the carb added a new battery and it started and runs good. Everything works as it should. My problem is it is smoking, it is a blueish whiteish smoke. It is worse at idle and pretty much clears up at wot. The tractor had been sitting a long time before I got it. I’m not sure where to start on diagnosing it.

I have a decent understanding how things work. I was thinking compression test. How would I check for a bad head gasket?




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It sounds like it is not too bad. I would change the oil to make sure it has the right weight in it and mow with it or work it for some time. At least then things will bet back to normal if it has sat for a while and you will have a better idea of how things really are.
 

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Blueish smoke is usually indicates oil burning in the cylinder. You didn't mention if you changed the fuel in the tank. Is it possible someone used 2 cycle fuel in there? Just thinking out loud because I came across a fellow with a similar problem recently and found out he was dumping Marvel Mystery Oil into his fuel can because he was told it would make his engine last longer........ I didn't ask him to elaborate. :mocking:
 

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I would run it for a while also. Rings may not be seating the best sitting so long, cylinder crud buildup and running it may work them back into the bore flat and raise the compression. Then do a cold and warm compression test to see how the pressure is. Have fun! More fun if you know it all works right before you put your money and labor into it. I still have to re/mount my modified Mower Deck on my Modified Craftsman's Mower to mow the fence line with this year. 100_1949.JPG 100_1843.JPG The Lawn Tractors are more fun and easier to work on for me. 100_1807.JPG 100_1791.JPG 100_1790.JPG .
 

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Discussion Starter #5
I cleaned the fuel tank and replaced all the fuel hoses. Should have mentioned that. I will try changing the oil and go from there. Although I probably have a month before I start mowing lol. But that will give me time to paint it.


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Discussion Starter #6 (Edited)
Update: changed the oil and it is still smoking white/blue after about 2 hours of use. The oil fill cap has a white milk inside it. I’m fairly certain it needs head gaskets or a full rebuild. What is the best way to tell if it is just head gaskets or a total rebuild? Compression test? I’d rather not tear it apart if I decide on a full replacement. I’m confident I could do the head gaskets but piston, rings etc maybe just be out of my comfort zone. IMG_7383.jpg


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You could try one of those hand pumps that hooks to the radiator cap. Pressurize it cold and hot. If it won't hold pressure, you know it's gonna need further investigation.

I would look closely at the intake gaskets before ripping the heads off.

Also, I have seen a couple of these 425/445's with a cracked cylinder liners.

Hope it's not that.

Good Luck!
 

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Your #1 diagnostic is pull the sparkplugs and have a look.
A compression test aint gonna tell much. A cylinder leakdown test will tell you more. You may be able to borrow the tool from an auto parts store. Also as previously mentioned, a cooling system pressure test should point out a bad head gasket. Remove the sparkplugs when you do the test. You may catch a glimpse of coolant seeping into the cylinder.
In my experience I have seen few blown head gaskets on the 425s.
Make sure your oil level is not over full.
As I said.. By reading the color of the plugs will just dang near tell you everything about how your engine is performing. Then use test tools to confirm.
Happy Hunting!

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Discussion Starter #10 (Edited)
So I did a leak down test. Both cylinders had air escaping from the oil fill but not the dipstick. Here’s my results with the plugs. The first 2 pics are #1 cylinder right side. Second 2 are the left side. Sounds to me like a bottom end issue. Thoughts?




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Not sure where you started out as far as pressures go but that is alot of leakage. I know it is in the green but anything over 20% is alot. Did you make sure valves were closed while testing?

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Discussion Starter #12
I hooked the tester up to shop air and then added pressure until the leak gauge was at zero. Then found tdc hooked tester to engine and took a pic of the results. I’m not 100% confident in the accuracy of the gauges. I think they’re off some. I turned the engine so the exhaust valve was open and the leak only went to about 80% leakage.

I guess the good news is the valves and head gaskets are good. I going borrow a compression tester this week and see what I get from that. That should confirm or deny the leak test results.


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Have you checked for coolant loss?
 

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I would run it for a while also. Rings may not be seating the best sitting so long, cylinder crud buildup and running it may work them back into the bore flat and raise the compression. Then do a cold and warm compression test to see how the pressure is. Have fun! More fun if you know it all works right before you put your money and labor into it. I still have to re/mount my modified Mower Deck on my Modified Craftsman's Mower to mow the fence line with this year. View attachment 680242 View attachment 680244 The Lawn Tractors are more fun and easier to work on for me. View attachment 680246 View attachment 680248 View attachment 680250 .
Very nice. Looks like a sheep in wolves clothing.
 

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If the oil looks as it does in your picture of the filler cap, then you have water/coolant entering the crankcase. Stop running the engine before you score crankshaft bearings or worse. Pull the heads and manifolds off and replace all of the gaskets. You can also check for cracks at the same time.
 

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Does the hour meter work as far as you can tell (they usually do on the 445 / 455 from my experience if the dash works)?

How many hours does it show on the motor?
 

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Discussion Starter #17
No the oil doesn’t look like that. I just changed it and the old oil looked normal.

It has 869hrs.


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No the oil doesn’t look like that. I just changed it and the old oil looked normal.

It has 869hrs.


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If the old oil looked normal, it obviously isn't getting much if any water into it. Was the oil "dirty" from normal use when you changed it and not like the guy changed it right before you picked it up?

Was the coolant level low when you got it? Is it using any coolant when you have run it?

Was it stored outside for long period before you got it? It doesn't appear so based upon the first picture in terms of severe fading, seat condition, etc.

Personally, if the oil doesn't look milky and it's not consuming coolant, I would run it with a half a pint of the Sea Foam in the crankcase and see if it doesn't clean up the smoking. Drain a little oil out before adding sea foam so its not over full. Could just be the rings are hung up.

Do you have access to a remote camera lead you can stick down into the spark plug holes to see the actual cylinder walls, etc.? If you do, I would visually look for signs of a cylinder scored from a broken ring or excess carbon build up on the piston or valves. Thinking even something like this, before you tear it down.....

Waterproof HD 2M/7mm Endoscope Lens Mini USB Inspection Camera with 6 LED Lights Borescope for Android Smartphone/PC/Lapt op - Walmart.com

I have known people who ran their equipment for YEARS on two stroke blended fuel because it was easier than wrecking their two stroke trimmers, saw and leaf blowers so they mixed all their fuel with two stroke oil.........Sounds like you have run it at least two hours so much of the excess should be removed from the cylinders and you said you flushed the tank.

Other then the smoke, does the engine run strong and have good power (not bog under load, etc)?

Also, in the two hours you ran the machine, did it use about 2 to 3 gallons of gasoline (1/2 a tank for that machine)?

I would also run some Sea Foam in the gasoline to help clean the fuel system if the engine is running strong and not consuming coolant or motor oil................
 

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Just FYI, according to the NGK spark plug fit guide, I am pretty sure they are calling for NGK BMR6a plugs. I am assuming that its the 20 hp Kawasaki which is stock to the 425.......I am not sure the difference between the BMR4a shown in the photos and the BMR6a, but I would assume it is heat range........You might want to start there before diving in to a tear down......
 

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What about valve springs and spring seals? At that many hours, depending on model year, it may need a cam replacement anyway. Usually a lot gets changed with the cam: valve springs, a bunch of seals, push rods, water pump, governor gear, oil pump, and valve cover gaskets. I did it myself and wasn't too bad, and I had never ever worked on an engine before. The front shaft seal was the trickiest to get to not leak after reassembly.

On mine, I noticed when I transported it (on some steep terrain), it would smoke a little until it burned off after being transported. But usually only for about 5-10 minutes. Don't know why it did that.
 
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