Talk:John Deere 420

It's a 1984, and it has the upgraded P220G engine

Model of 1980s

Known Issues Forum Post

1) Check the differential case. The early 420s had two bolts holding it to the cross member that attached to the frame. When the frame flexed it sometimes cracked the case. They later went with a one bolt slotted design because of this. My case was cracked but had been welded.

2) Early 420s had a front PTO tensioner that was attached to the side of the frame. It's kind of hokey and make sure all of the parts are there and it works.

3) In 1983 the steering column was a 4 port instead of a 5 port. The big difference between them was how the fluid got to the steering column. On the 4 port the fluid went through the H3 valve first and on the 5 port it went to the steering column first. hat can happen is when lifting an implement (like the front blade) steering will become less responsive .

Onan B48G replacement motor

Here are a few options for repowering a John Deere 420:

Kohler Engines: Kohler offers replacement engines that can be used in John Deere 420 tractors. The Kohler Command series engines are a popular choice for repower kits.

Honda Engines: Honda engines are known for their reliability and may be available as part of a repower kit for the John Deere 420.

Briggs & Stratton Engines: Briggs & Stratton also offers engines that can be used to replace the Onan B48G.

Several companies specialize in repower kits for John Deere tractors, including:

Repower Specialists, Ltd.: They offer complete repower kits with Kohler engines specifically designed for John Deere models. Small Engine Warehouse: They provide repower kits and individual engines for various applications, including John Deere tractors. When considering a repower kit, ensure that it includes all necessary components and instructions for installation to make the process as smooth as possible.

Onan B43G in 420 vs 318

The B43G used in the JD 318 has 2hp less than the one used in the JD 420. The difference is in length of stroke by the piston/rod/crank.

B48, P220, or a P224, just make sure of the crank will fit PTO and the drive shaft length

The b48g are harder to find, in any case if my original engine fails will spend the money for a rebuild rather than buying a spare.

B&S Vangaurd engine

repowering == replace engine

repowering with anything but another Onen. Don't! Everyone I've talked to who have empowered their 318 or 420 have regretted it. I know someone who replaced his BG48 with a 23.5 Koehler. Says it just doesn't have the power it had with the Onen.

wouldn't repower with a different brand engine unless you need or desire a significant increase in HP and/or torque. Seeing as these machines were designed and optimized around the 18-20hp engines, anything more than that probably isn't very useful for most of us.

most Honda engines are built in China and I suspect the Predator is an exact copy of the Honda engine that they build for Honda.

research the onan b48 engine

smoke at startup and smell fumey all the time

Probably needs a head and valve decarbon job done, followed by valve adjustment. You might want to check the compression and check it to the minimum spec. Do you have the TM1590 and CTM2 manuals

Per the JD Tech. Manual 1590, minimum cylinder compression for the B48G is 100 psi per side & no more than 10 psi difference.

Smoke at start-up is pretty normal. So is the smell. The engine is an older flathead design that most people that know say yeah; are dirty, use more gas, etc., but can be rebuilt\repaired over & over, albeit not always cheaply. At 600 hrs. yours could probably benefit from a "decarbon job" & maybe is running rich -- an overhaul, that includes all new gasket & seals = could make it as good as it was new. 600 hrs. isn't a lot. True - now days, mechanics at JD dealerships usually don't have much experience working on a vintage machine like a JD 420 L&G tractor.