john deere compression test

I have a vintage 1967-70 john deere 112 with a I believe is a 8hp Kohler engine I did a compression test and I got a 82 pound reading is that good and will the engine start with that reading ?? I appreciate any help johnny

Because small engines have a decompressor that works at cranking speeds and because the actual amount of decompression will vary according to the actual valve lash, strait compression testing is some what meaningless.

So what is actually happening when you try to start it ?

Usually when presented with a non starter I fit an inline red spark tester and then squirt a short shot of carb cleaner down the plug hole.
Pull the cord.
If the engine goes bang the the timing is OK & the sparks are OK.
If the tester flashes but there is no bang, try again with a new plug.
From here it depends upon what & where the bang was.
If it was "normal" then repeat but spray down the carb
If the engine runs for a brief second then the valve timimg is also good & you need to look at the carb
If it backfires through the carb then the valves need attantion
Ditto for after firing out the exhaust.

thank you so much for the information ….johnny

451johnny said:

I have a vintage 1967-70 john deere 112 with a I believe is a 8hp Kohler engine I did a compression test and I got a 82 pound reading is that good and will the engine start with that reading ?? I appreciate any help johnny

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I work at a dealership and 112's could have either a Tecumseh or Kohler.

Can you verify what engine you have? I have attached the serial number and engine info below.

To answer your question, the engine may run at that compression depending on what's wrong.

For instance, my 1964 110 (that my great-grandfather bought new) had similar compression a few years ago. It would run, but I couldnt adjust the carb enough to get it to run smoothly.
Long story short, I did a leakdown test on the engine and discovered the valves were leaking. I removed the cylinder head and did a valve job, and it has been running great ever since.
On the other hand, I had a 1973 model 140 a few years back that also had a Kohler with similar compression. It's issues were a mixture of valves and worn rings.
The engine would run, but it was low on power and had blue smoke coming out the muffler and crankcase breather as it ran. That engine got a full rebuild.

I would recommend doing a leakdown test on your engine and see where it's leaking.

1. If air blows out the carb, the issue is the intake valve.
2. If air blows out the muffler, the problem is the exhaust valve.
3. If air blows out the dipstick tube, then you have worn rings.
4. You may have air blowing out one or more of the above, but at least you will know what the issue is.

This test will eliminate any guess-work and help you pinpoint the issue.

If you have a Tecumseh, they were known for needing to adjust the valves more often than a Kohler.

Hope this helps!

Will

it's a Kohler ..and thank you so much for that valuable information....johnny