Standard engine compression issue

I have a 1950s Standard twin garden tractor that me and my dad have been trying to restore in the past few months and it refuses to start we had the carburetor cleaned and restored as well as the magneto rebuilt and the timing should be OK because we did not tamper with the mounting plate that the magneto is on. But me and my Dad tested the compression via a compression tester and we are just peaking 25 psi on the gauge and we know that the compression is suppose to be in the 75 to 100 range and the head gaskets are in decent condition and we grinned the carbon off the valves and it's still just peaking 25 psi ???

Any suggestions? :?

Valve lash , decompression stuck open , don't know what engin e
It is so that 's it if you got spark

When checking the compression, was the throttle wide open? if not, it will be low reading. The cylinder/s must fill easily
to get a reading. How fast was it being cranked? with less than 100 RPM, the compression will leak as well. Just because
it was not adjusted does not mean it was OK before unless it ran. With the plugs out put a teaspoon of ATF in each cylinder
and rotate the engine through 15 full turns. Let it sit for a day or two )plugs loose and in. then put a tablespoon of
gasoline in each cylinder followed by the plugs and try to start it. Jim

Thank you Jim and Dennis I will talk with my dad and keep you all updated.

you are asking a question that needs a visual analysis , as you said you ground the carbon of the valves. well how do we know what you have done. you could have damaged the valve seat. carbon is either soaked off or can use a wire wheel. no grinders allowed! also is the valve lash set? if the valves are at zero lash for example they might be just not quite seating. you can read the valve seats to see if the problem lies there or not. there is lots a person can see with the eye instead of guessing at different things. and also many time there is so little info given on a problem thats why it involves so much guess work. everybody says it could be this it could be that but it all a guess. when you look at things visually the experienced can see problems that the not so experienced can not see, or have no idea what to look for.

It is kind of odd that you had that low of compression on all cylinders.

Are you sure the valve clearances are set?

Did you have the cam out?

(quoted from post at 16:28:53 04/22/16) I have a 1950s Standard twin garden tractor that me and my dad have been trying to restore in the past few months and it refuses to start we had the carburetor cleaned and restored as well as the magneto rebuilt and the timing should be OK because we did not tamper with the mounting plate that the magneto is on. But me and my Dad tested the compression via a compression tester and we are just peaking 25 psi on the gauge and we know that the compression is suppose to be in the 75 to 100 range and the head gaskets are in decent condition and we grinned the carbon off the valves and it's still just peaking 25 psi ???

Any suggestions? :?

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I had a Datsun 510 years ago that had one cylinder out of 4 that had little to no compression. It turned out that the head gasket was leaking and the rings on that cylinder were stuck. I drove it to the parts store and bought a can of Alemite Detergent Concentrate (CD2) and dumped the can into the crankcase in the parking lot, I then drove it 60 mph to the next town (15 miles, round trip) and ended up back at home where i changed the oil and filter. When I checked the compression again they were ALL good! And they stayed that way after I dealt with the head gasket issue.
About 5 years ago I had the rings seize (single cylinder and NO compression) on an air-cooled motorcycle engine due to starting and riding it with old, separated gas in the tank (I figured that the seizure came from running i until hot and then shutting it down and letting it cool). This time, I poured some CD2 into the sparkplug hole and kicked it over slowly 5 or 6 times, then let it sit for an hour or so. Dumped out the old 'gas', refilled with fresh and it started and ran as normal then.

The point being is that it's possible that your engine's ring are stuck also - due to many variables which may or may not exist now (Old, bad gas has been replaced, etc.). Good Luck to you!

pour a couple table spoons of oil in the cylinder and check it again, if the compression comes up it's the rings,..if it doesn't it's the valves

Swap the plug wires. Make sure you're getting fire to the plugs. I had several of those tractors. Hal

Swap the plug wires. Make sure you're getting fire to the plugs. I had several of those tractors. Hal