Yanmar low RPM under load

[casual]

ADJust the valves . If not WAY out of adjustment , bite the bullet pull the head . Carbon build up will not cause your problem.

[Compass790]

Originally Posted by jmurray109

Attachment 174990

So I forgot to mention that a chunk of the air filter was missing. It is unknown if this was new damage or has been like this for a while. That leads me to the next question. I have removed the air intake manifold and did not find anything. I have tried to dig out any debris from the intake and did not find anything that lead me to believe that I found all the missing pieces. I have tried compressed air to blow it out and also a vacuum. So it is still possible there is a large chunk down deep. What are my next options? This is the only thing that I have not ruled out as a possibility as a blockage. Someone also mentioned if not air intake that it could be something wrong with fuel governor. I am really tried to find something else wrong before saying that the #2 cylinder is dead. Any other suggestions would be appreciated. Thanks again.

Dont know what part of yr aircleaner has come off but I have seen a case where a bit of the mesh got jammed under a valve thereby causing loss of compression. Do the valves on the problem cylinder move up & down normally? Do they end up at the same height when they have clearance from the tappets?

[jmurray109]

I removed the head and checked the valve seals. The exhaust valves did not show any signs of leaks. The intake valves had leaks. The number one intake valve had a leak and the number 3 valve had a slight leak. The number 2 just had a sign of moisture around the edges.

https://m.youtube.com/watch?v=knz6CmfcV9c

[jmurray109]

https://m.youtube.com/watch?v=FMEhQnxU1xc

[jmurray109]

[jmurray109]

Does anyone see anything that stands out.

[Compass790]

Originally Posted by jmurray109

Does anyone see anything that stands out.

The leak is bad, you have to grind valves, Unusual for intake to go before exhaust. What are the seats like?

[jmurray109]

Originally Posted by Compass790

The leak is bad, you have to grind valves, Unusual for intake to go before exhaust. What are the seats like?

I am taking to machine shop to have new values installed. Hopefully this was the cause of the original problem.

[Compass790]

Originally Posted by jmurray109

I am taking to machine shop to have new values installed. Hopefully this was the cause of the original problem.

Good chance that is your smoking gun but check everything whilst you have it apart. Good luck

[MikeFergie]

From your picture of the block with the pistons it looks like no 3 piston is carboned up bad (or is this loose dirt from taking the head off ?)
Yet from your head picture you have leaks through your no 1 cylinder valves but the no 1 and 2 pistons are clean.

A piston gets carboned up when it does not combust. This could be valves or the injector !

[Compass790]

Originally Posted by MikeFergie

From your picture of the block with the pistons it looks like no 3 piston is carboned up bad (or is this loose dirt from taking the head off ?)
Yet from your head picture you have leaks through your no 1 cylinder valves but the no 1 and 2 pistons are clean.

A piston gets carboned up when it does not combust. This could be valves or the injector !

I think you are lookn at it the other way frm the vid. orientation is different frm pic. I thought carboned piston was No 1 but maybe its my orientation!

[MikeFergie]

I was looking at the orientation of the head to the block. This show the leaking valves at the opposite side of gummed piston.

Yes opening my 3ym30 manual it shows pushrods on the right oil filter on the left so it’s the front piston not looking like it’s firing well. But if you match the head it’s the rear cylinder valves leaking

[Compass790]

Originally Posted by MikeFergie

I was looking at the orientation of the head to the block. This show the leaking valves at the opposite side of gummed piston.

Yes opening my 3ym30 manual it shows pushrods on the right oil filter on the left so it’s the front piston not looking like it’s firing well. But if you match the head it’s the rear cylinder valves leaking

I do believe you are right! I apologise for questioning your orientation. I can only say in my defence that i was drinking beer whilst posting. However, as you pointed out, that means more problems for the OP sadly.

[MikeFergie]

Carboned piston caused by poor or no combustion
Causes - leaking valves
- rings not sealing
- injector not putting in enough fuel or not atomized fuel

[a64pilot]

It’s been my experience that carbon comes from burning oil. Especially if it’s greasy at all.