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Old 08-03-2020, 21:58   #1
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Yanmar 2gm20 Compression levers

I need clarification on the correct positions for the levers too start. My understanding is when the front lever(near the water pump) is. pushed forward towards the center of the engine, and the rear
lever is also pushed forward towards the center of the engine this is the compression scenario. However my front lever feels likke its not hooked up. I can feel no resistance or click. Also when I hand crank it immediately pops back to the other setting. The rear lever has a distinct feel with changing it and stays in place. Is all this. normal? And yeah the engine wont run.
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Old 08-03-2020, 22:27   #2
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Re: Yanmar 2gm20 Compression levers

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I need clarification on the correct positions for the levers too start. My understanding is when the front lever(near the water pump) is. pushed forward towards the center of the engine, and the rear
lever is also pushed forward towards the center of the engine this is the compression scenario. However my front lever feels likke its not hooked up. I can feel no resistance or click. Also when I hand crank it immediately pops back to the other setting. The rear lever has a distinct feel with changing it and stays in place. Is all this. normal? And yeah the engine wont run.
Welcome aboard CF, juneau kid.

Unless hand starting (with the crank handle), both levers should be left pushed aft. This is the normal position (i.e. compression).

If both levers are pushed towards the front of the engine, each cylinder is decompressed and it becomes possible to turn the engine over using the hand crank.

If you wish to start the engine with the hand crank, decompress both cylinders (i.e. moving both levers towards the front). They should stay in this position as you crank the engine over by hand. When you have it turning fast enough, have someone move one of the levers aft (i.e. compression position) while continuing to crank the engine. When it fires, move the other lever back to compression so both cylinders will fire.

It isn't easy, it takes a certain knack.

I assume the engine starts and runs OK when using the electric starter motor. If not, fix that first before attempting to learn how to hand crank.
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Old 08-03-2020, 22:37   #3
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Re: Yanmar 2gm20 Compression levers

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..... However my front lever feels likke its not hooked up. I can feel no resistance or click. Also when I hand crank it immediately pops back to the other setting. .........
The levers act on the exhaust valves - holding them down a bit.

If the exhaust valve is already fully open, you won't feel it pushing it open - nevertheless, the lever should remain in position as the exhaust valve begins to close.

Take the valve cover (AKA rocker cover or bonnet) and look inside it. The mechanism is quite simple and both should look exactly the same. If the front one is faulty, it should be very obvious.
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Old 09-03-2020, 03:07   #4
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Re: Yanmar 2gm20 Compression levers

Greetings and welcome aboard the CF, kid.
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Old 09-03-2020, 12:53   #5
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Re: Yanmar 2gm20 Compression levers

According to the YANMAR USER MANUAL, the compression release lever should be in the DOWN position, which is FORWARD towards the Front of the engine for COMPRESSSION....

Raise the levers, moving them up and toward the rear of the engine for DE COMPRESSION...
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Old 09-03-2020, 15:53   #6
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Re: Yanmar 2gm20 Compression levers

Mea Culpa - my above post about the positioning of the decompression levers was incorrect .

A big thank you to dennismenace111 for posting the correct information.
He wisely relied on the Yanmar Manual and I had foolishly relied on a faulty memory and an old photograph I had of my 2GM20 of some back. I now realise I had taken the photo while doing some maintenance and the levers were in the decompressed position at that time. I should have consulted the manual and not my memory.

One of the good things about CF, almost always someone corrects another's errors, this helps us all

For the OP, here are some extracts from the service manual and if you don't have the 2GM20 operation manual, I would encourage to get one. There is a wealth of information in it. The photo of the engine shows the levers in the decompressed position.

My apologies to juneau kid for confusing the issue.
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Old 10-03-2020, 16:13   #7
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Re: Yanmar 2gm20 Compression levers

Here I thought it was one of my Easter European ancestors ghosts messing with my memory till I checked the manual! Then I started thinking,. Maybe this is why my engine has some excessive blowby and sir pressure under the valve cover cause my decompression levers are wrong!

In any case.. no harm done!
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