4030

bmiller36 · Feb 9, 2022

I have a gas 4030 and want to check the Compression, but I cant find the specs in the IT manual. Thanks in advance Bob

VicS · Feb 9, 2022

Have you checked compression. All cylinders should be almost the same. Carb should be wide open. To check rings put some oil in each cyl. To bring the low ones back. If a valve won't make any difference. Check valve lash first. I check with all plugs out. Looks like they only made them in gas just one year

Bob Bancroft · Feb 9, 2022

Charger on the battery also so cranking speed stays consistent throughout the process.

Janicholson · Feb 9, 2022

Add charged battery to promote good cranking speed. A uniform number of strokes to reading (6) works. Jim

Tech 7 · Feb 9, 2022

And destroke the front pump

Pete in MD · Feb 9, 2022

According to Service Bulletin 181-S only the plug on the cylinder being tested should be removed. Removing all plugs would result in a faster cranking speed and thus a higher compression reading.

Above info was for the old 2 cylinders but I don't see why it wouldn't apply to all gas engines regardless of the number of cylinders.

deere4040 · Feb 10, 2022

Get rid of the IT manual and get a JD service manual. There is a reason they are 4 times thicker. Well worth the money.

BarnyardEngineering · Feb 10, 2022

The specs are "more is better."

Generally speaking you need about 50 to run. 75 for the engine to start without being dragged around the yard by another tractor. 90 for it to have any power at all. At 100, you stop scowling and say, "Hmm that's not bad." At 120, you crack a smile and say "That's pretty good." At 140, high fives all around. At 160, bust out the champagne.

What's most important is the readings are fairly consistent across the cylinders. Ideally 10% variation at most, but engines will run with much larger variations. It's all about what you want out of the project.

I've never really noticed a difference between carb open and carb closed. I've never really noticed that it matters much whether you do the exact same number of cranks for each cylinder, or just go until the number stabilizes. We're checking compression here, not aligning a particle collider.

Texasmark · Feb 10, 2022

Funny you make that comparison.

I spent 2 years as part of the Linear Accelerator design/installation team on the Superconducting Super Collider down in
Waxahachie, Tx. back in the early 90s before congress closed it. The aim for two wads of ions traveling in opposite directions
around the loop, at the speed of light, was to be controlled by superconducting magnets, running at 4* Kelvin. with Cryogenic
Cooling stations every 5 miles in a 54 mile circle.

The viewing towers were where they would flip a switch and cause the wads of ions to smash into each other and the scientists
were there to see the Quarks, Top Quarks and other things spewing out of the collision. Cern Laboratory in Switzerland was doing
and completed the same thing but in an 18 mile circle....if my memory is intact for all of this. The idea was to explore the origination
of matter....see if they could figure out where everything originated.

4030

bmiller36

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VicS

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Bob Bancroft

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Janicholson

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Tech 7

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Pete in MD

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deere4040

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BarnyardEngineering

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Texasmark

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