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Discussion Starter · #1 ·
Hi all,

I grew up running my grandad's 400 to mow his 10 acres until he upgraded to a Scag Turf Tiger with a 72 inch deck.

When he passed in 2018, I inherited his scag and mowed my half acre with it for a while, but it was definitely overkill and had a tendency to scalp my yard in spots. So with 1900 hrs on it, I decided it was best to sell it while it was running as they can be pricey to repair.

I decided I wanted to go back to a garden tractor so I could do a little more than just mow with it.

While I had my scag listed for sale, I decided to start looking for a John Deere garden tractor. I started looking for a 318 as I figured I would like the smaller size and the ability to store it easier in my garage (my biggest gripe about the 72 inch deck). Most I found were either priced too high in my opinion or had to many hours for my liking.

I stumbled on a 420 about 4 hours from my house that had an honest ~550 hours on it. So, I sold my scag got a trailer and went to look at the 420.

It ended up coming home with me. Seems to be an honest 500 hours. Runs great, no smoke and only one minor leak at the rear right wheel.

I did end up adding the starter relay so it starts easier.

Very happy with it so far, going through and doing a little maintenance items as I go.

Sorry to be long winded. Here are a few pictures, and yes I found a used grille to fill that hole.
 

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Nice find. I’ve owned 3 420s over the past 10 years and you’ve made a good decision. It appears that it has the original GoodYear tires which is consistent with the “true hours”. To keep the Onan running without major issues keeping it cool is critical. To do this pull the engine to clean up the debris/oil around the cooling fines, install a Mylar fire wall as the original one degrades and becomes useless and get an oil filter air seal. Oil is cheep versus a rebuild so I change it every 25 hours.

I would also clean the fuel tank, replace pick up filters using yellow Tygon tube for inside the tank (Stens 115-410) and replace all fuel lines.

If you plan to get front attachments replace the quick connects. It’s a PIA especially if the bumper is bent but worth the effort.
 

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Discussion Starter · #4 ·
Nice find. I’ve owned 3 420s over the past 10 years and you’ve made a good decision. It appears that it has the original GoodYear tires which is consistent with the “true hours”. To keep the Onan running without major issues keeping it cool is critical. To do this pull the engine to clean up the debris/oil around the cooling fines, install a Mylar fire wall as the original one degrades and becomes useless and get an oil filter air seal. Oil is cheep versus a rebuild so I change it every 25 hours.

I would also clean the fuel tank, replace pick up filters using yellow Tygon tube for inside the tank (Stens 115-410) and replace all fuel lines.

If you plan to get front attachments replace the quick connects. It’s a PIA especially if the bumper is bent but worth the effort.
Thanks for the tips.

I've pulled the screens on the dash and got all grass and crap out from in front of the fan.

I haven't removed any of the metal off the engine to inspect, but appears to be pretty clean. I blow it off good after each use.

I did just purchase a new air filter and the foam pre cleaner in addition to a new oil filter and the grommet that goes around it.

I also got two new Deere front PTO belts.

The previous owner said he just went through the deck and it is quiet, but I believe I'm going to install a new set of Deere blades and a new Deere belt on the deck. While I've got the deck off, I'll change the gear case oil and grease all the fittings on the tractor.

I'm super impressed with the turning radius on this rig too. It will cut on a dime!
 

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Yanmar clacking
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Great 420 you got there! I’ve got a 430, so kind of the same (just a little bit longer on the end lol). The 400 series are beasts
 

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The 420 is a great tractor. They lack a few of the features found on the newer tractors of comparable size on the market today but still a solid performer. I have two of them. I'll probably never sell either of them. Good score of finding that one.
 

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If going to spruce it up per se, you ought to also consider adding the partition "firewall" insulation.
Longtime WFM member John Lang has provided Mylar faced kits and may even have a type that can be installed without moving a lot.
email: [email protected]

Motor vehicle Green Wood Grass Automotive exterior
 

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Discussion Starter · #9 ·
If going to spruce it up per se, you ought to also consider adding the partition "firewall" insulation.
Longtime WFM member John Lang has provided Mylar faced kits and may even have a type that can be installed without moving a lot.
email: [email protected]

View attachment 270350
Thanks for the tip. I actually ordered one today from Mr. Lang after a google search.
 

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Discussion Starter · #10 ·
Came home wanting to mow the yard tonight..... well that didn't happen.

I'm getting the grinding or humming noise from the starter and engine won't turn over. I know the battery has good voltage and I put battery jumper onto cables.

I think it's time to cut my losses and just replace starter. Sounds like it's time to pull the engine.

Wish me luck!
 

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Yanmar clacking
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Came home wanting to mow the yard tonight..... well that didn't happen.

I'm getting the grinding or humming noise from the starter and engine won't turn over. I know the battery has good voltage and I put battery jumper onto cables.

I think it's time to cut my losses and just replace starter. Sounds like it's time to pull the engine.

Wish me luck!
Dang, that’s tough luck! Good luck on the engine pull, and let us know what happens
 

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Discussion Starter · #12 ·
Jumped the gun a little prematurely. Decided to go back and check the key switch again. Pulled the connector off and cleaned it with MAF sensor cleaner on all the plugs, then it fired right up while cranking.

Dodged a bullet so far on this one! Lol I might replace the key switch if I continue to have issues.
 

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Jumped the gun a little prematurely. Decided to go back and check the key switch again. Pulled the connector off and cleaned it with MAF sensor cleaner on all the plugs, then it fired right up while cranking.

Dodged a bullet so far on this one! Lol I might replace the key switch if I continue to have issues.
Great save! I love when it’s a simple fix
 
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May be wise to replace the ignition switch "key start" anyway - considering the age of the tractor and especially if it's the original. 20-25 bucks.
 

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You mention a grinding noise in your starter. It’s possible the starter bendix is sticking and not engaging the flywheel teeth cleanly as it extends. If you can spray it with some cleaner/lube, sometimes that helps.
Oftentimes when the switches and wiring connectors in these tractors age, the ignition switches, wiring and connections corrode slightly and cannot pass current like before. There is a recommended fix called “Starter Improvement Relay” that provides a wiring path from the battery through a 12V automotive relay to the starting circuit, avoiding the need to pull as much current through the ignition switch and wiring.
Search this site and you will find many references to this upgrade, installation instructions and benefits.
 

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Discussion Starter · #16 ·
You mention a grinding noise in your starter. It’s possible the starter bendix is sticking and not engaging the flywheel teeth cleanly as it extends. If you can spray it with some cleaner/lube, sometimes that helps.
Oftentimes when the switches and wiring connectors in these tractors age, the ignition switches, wiring and connections corrode slightly and cannot pass current like before. There is a recommended fix called “Starter Improvement Relay” that provides a wiring path from the battery through a 12V automotive relay to the starting circuit, avoiding the need to pull as much current through the ignition switch and wiring.
Search this site and you will find many references to this upgrade, installation instructions and benefits.
I've already installed the relay you mention.

That was my original fix.

I'm not sure if grinding is the correct term for the noise, but I'm sure cleaning of area couldn't hurt anything. Can you access it with any sort of spray?

I believe most of my issue has been current through the key switch and old worn or dirty contacts in the switch.
 

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Sorry I missed seeing that you already installed the starter improvement relay. It's been a while since I last worked on a 420. I'm not sure if you can access the bendix externally with a cleaner spray but it's worth checking.
 

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Discussion Starter · #18 ·
Sorry I missed seeing that you already installed the starter improvement relay. It's been a while since I last worked on a 420. I'm not sure if you can access the bendix externally with a cleaner spray but it's worth checking.
Not worries or reason to be sorry. I'll take any advice I can get.

I think it is actually the plug on the switch getting dirt in it. I've cleaned it and it hasn't missed a lick since. I've started it 4 or 5 times in the garage with no issue.

I think it does need to be cleaned over all though. There is some dust that needs to go.

Just the nature of older air cooled engines. I think I'll pull the battery and the tray and clean it out really well.
 

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Discussion Starter · #19 ·
Mowed the yard tonight. No issues starting. I went ahead and ordered a switch just in case for $22.

I plan on cleaning up the tractor this weekend and cleaning out really good in the tower area.

I also got the insulation kit for the firewall from Mr. Lang in the mail today.
 

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Good news on the engine starting tonight and good plan to clean and install the insulation.
If you follow jg316’s advice in post #2, I think you’ll be very happy with the results and the engine will run cooler.
You know how much dirt and debris you can see in the tower area. Now think about the dirt and debris that did not get deposited there but instead got pulled into the flywheel intake and pushed across the engine block. Some of that dirt most likely got caked into the cooling fins on the block, especially if there was an oily spot. Pull some tins off the engine and check.
 
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