Compression tester

[Mark Poss]

Where can I find a compression tester that threads into the cylinder of an unstyled John deere A? I have a tester with a rubber end on it but it doesnt work so well and all of the threaded fittings for it are to small. Thanks for your time, Mark.
 

[leon]

Make one out of a used spark plug?
 

[McBride]

NAPA
 

[pbb]

Mark I am needing to check my compression in my 37A too. I was going to make a adaptor out of a old plug.My tractor is running on one cylinder and has lots of blow by.When it warms up some im going to check mine.How would be the best way to check a hand start?Im thinking getting someone to pull it like if you was to pull start it and then i could walk beside it and read the gauge.I dont know if hand cranking it would be fast enough to get a good reading.
 

[Cliff Nelson]

You're right that hand cranking would be too slow. Pulling it will be ok but you need to determine the correct speed for the test. Too fast will show higher compression.
 

[Mike M]

Hook TWO together using a flat belt on the belt pulleys. Best way to turn them for tests.
 

[alvan]

I got mine at Sears and it came with adapters to work for all sizes. Also holds reading until you release it nice if you are doing it by your self.
 

[BushogPapa]

Compression is so low on a Hand-Start JD that a compression test should not be necessary...YOU can tell if the cylinders are Leaking down badly..

Maybe the appropriate question should be: How fast of a leak-down would be too much..
If you need to turn it over fast, to feel compression..it is leaking down too fast..!!
You should feel little, to no leak-down with a good Fresh engine..
Accumulated carbon, debris and burning from leaking gases will allow valve leaks long before ring wear would be the cause..BUT...
If the time of the last re-ringing is totally unknown, put new rings in when the head is off for valve-grinding...it is pretty easy and may not be as good as a re-bore, but with GOOD Honing, will improve the compression for many years..certainly until it needs another Valve-Job...
A "GOOD" Valve Job is not necessarily what you will get at JD..
I had to re-do a JD 50 head that JD had done...
They had simply dropped New Intake valves on to UN-re-conditioned seats, and those seats were the absolute worst-looking rusted, pitted seats you will see (and they called it a "Valve Job")..
Take it to someone who Will do a good job..!!

Ron.
 

[Ray]

Harbour freight sells a cheap one.It has several fittings.
 

[pbb]

Im wanting to check mine because the #2 cylinder when petcocks are open when tractor is running isnt hitting as hard as #1.When running i can pull the plug wire to # 2 and no change.When i pull the plug wire to # 1 it dies.I got new plugs, wires, points ,condencer and rotor.It ran the same with the old stuff.I was going to see if theres 10 percent difference between the two.If it is im going to tear it down and have the head done and new rings.The tractor was my dads and sat for years.So i dont know if it has stuck rings or a broke ring and it could be in the valves.My dad was fixing it up and he passed before it was done so I dont know what he was going to do with it.He lived over 300 miles from me and i didnt make it up there much.Now i got the tractor and im going to finish it out and keep it in the family.
 

[Determined]

If your ignition is good as you indicated and it dies when you pull the wire to cyl 1 then you already answered your question.
If both cylinders are within 10% of each other, it should keep running on either one.
 

[gtx1967jewison]

Hand cranking it works fine. Make sure the throttle is wide open. Run it through about 3 cycles with a tester that holds the pressure. They need very little compression to run nice if your carb is set right & ignition is strong. To strengthen #2 try richen the idle mixture. Turn the idle mixture needle counter clockwise a full turn or more & see if it gets stronger or just smokes. I suspect weak ignition if that dont help. A sticking valve is also possible