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The easiest is to probably take an old spark plug and knock the porcelain out and braze it to a fitting you have for your tester.

Spark plug is kind of a pre chamber deal on these not sure you will see the compression number that’s real like on most other engines, be interesting to hear what others think on this🍿

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1 hour ago, hardtail said:

The easiest is to probably take an old spark plug and knock the porcelain out and braze it to a fitting you have for your tester.

a current  90> model ,$5 champion of correct base , not a long reach cleanable OEM

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2 hours ago, hardtail said:

The easiest is to probably take an old spark plug and knock the porcelain out and braze it to a fitting you have for your tester.

Spark plug is kind of a pre chamber deal on these not sure you will see the compression number that’s real like on most other engines, be interesting to hear what others think on this🍿

My book shows the compression ratio in diesel mode as 2 1/2 times that in gas mode and compression as above 400 psi @ 1000 rpm.  I assume that's in diesel mode.  I guess that seeing some kind of pressure in gas mode would indicate to me that all three valves are at least partially working.

Vic

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At least you could compare the reading to other cylinders 

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18 minutes ago, hardtail said:

At least you could compare the reading to other cylinders 

Thanks---I had thought of that.  If the cylinder isn't completely dead of pressure, I'll do it.  First, I've got to come up with a compression tester setup.

Vic

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17 minutes ago, mmi said:

you should have no pressure on diesel,lest the valve is warped

I understand---I don't intend to check for pressure out of the spark plug hole in diesel mode.

Vic

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9 hours ago, thebunns said:

I understand---I don't intend to check for pressure out of the spark plug hole in diesel mode.

Vic

I assume that you are talking about checking for pressure in the spark plug hole when in diesel mode.  That would tell if the decompression valve is working properly or not.  I've already done that check by sticking my finger in the spark plug hole & turning the motor over in diesel mode.  It's working fine after I unstuck it.  Right now I'm going after the other two valves because the #1 cylinder won't fire in either mode.  I'm slowly working my way to pulling the hood & valve cover to check for clearances (broken spring?).  Everything is tough when it comes to working with the cylinders as I can't crank the motor.  The hydraulic pump is in the way.

Vic

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12 hours ago, thebunns said:

I understand---I don't intend to check for pressure out of the spark plug hole in diesel mode.

Vic

test both ways with GOOD batteries.

others reading may not know or confirm function,as in past have ,some been closed, read 25 psi and  tossed project due to a little carbon on valve.

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in diesel mode compression is zero and thats what you want. you can even remove the plugs in diesel mode when running and must be absolutly no pressure. in gas mode its just the standard compression check , still should have 90-100 lbs  those small ags valves are know for warping by being left open on a shout down when hot. shutting down in diesel mode after a 15 minute idle is the ticket, after a warm work out.

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51 minutes ago, rustred said:

in diesel mode compression is zero and thats what you want. you can even remove the plugs in diesel mode when running and must be absolutly no pressure. in gas mode its just the standard compression check , still should have 90-100 lbs  those small ags valves are know for warping by being left open on a shout down when hot. shutting down in diesel mode after a 15 minute idle is the ticket, after a warm work out.

Exactly!!!  I've always shut both tractors down in diesel mode after cleaning the dirt (mud) from the top rollers & backing them into the barn.  That takes several minutes.

Vic

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  • 2 weeks later...

OK folks, here it is---the adapter for checking compression.  It's a metric nut welded onto the gutted out spark plug.  The compression gage hose screws into it.  Testing is next & I'll have some numbers to share.

Vic

6.JPG

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I now have an adapter for the compression tester, have tested all cylinders & got 80-100 lb. pressure.  The problem is that I forgot to install the mag with the new coil so don't know where the timing is.  I punched the starter until I got air out of the #1 plug hole and set the mag accordingly and installed it.  Nothing!  I pulled the mag & rotated the rotor one position, and another and another but no pop.  The #1 spark plug is getting a good spark.  I pulled the plug, turned the engine over with my finger in the plug hole.  It was dry.  Question---shouldn't I have gas spraying on my finger?

Vic

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