yanmar GM10 wont start

[RichardS]

And I don't go along with Richard's comment of the oil being added to help starting acting as easy start. It needs to be atomised, unlikely with a bit of 20 40 squirted in the intake. That works to seal worn rings/bore.

Where has anyone suggested engine oil?

I merely evinced a suspicion that the oil might be acting as fuel. Unless I saw it myself, it remains conjecture because I'm assuming that the engine in question is a standard GM10. Putting oil into the intake and expecting it to seal the bore is not easily envisaged and would require a lot of oil and a lot of cranking if the oil was ever going to find it's way through to, and then past, the intake valve in sufficient quantity to increase compression before being combusted. If the engine starts with a normal period of cranking then the oil is probably acting as fuel.

Either way, that's all irrelevant. I am responding to post #34 and the point I am making is that it would be madness to simply rush in and remove the cylinder head without checking whether a valve is stuck once one has access to the valve gear.

Richard

 

[earlybird]

[QUOTE="RichardS, post: 7708279, member: 38107"
it would be madness to simply rush in and remove the cylinder head without checking whether a valve is stuck once one has access to the valve gear.
Richard
[/QUOTE]
Whether or not a valve is sticking seems irrelevant. Either way I'd take the head off, some of the suggested approaches to unstick a valve might result in the valve in question becoming bent by being hit by the piston. (I'm unsure of GM head clearances).
A new gasket is <£25 and gives the opportunity to, at least grind in the valves from which, on the face of it, this engine would benefit.

 

[RichardS]

Whether or not a valve is sticking seems irrelevant.

We have hereby formally agreed to disagree about whether a sticking valve is relevant or not.

Richard

 

[179580]

I suspect that the oil might be functioning as "easy start" to start the engine rather than sealing the bore but, either way, I would still check for a stuck valve before rushing to remove the head as it's part way through the same process.

Richard

Let me explain my reasoning.
The engine, historically, needs assistance to start. Even before this perceived valve problem.
Be it bore sealant or "easy start" ? Since time imemorial the technique has been used by skilled engineers to assess compression loss.
Freeing a sticky valve is not going to solve the historical problems.
Not to address the underlying problems is a short time botch.

 

[RichardS]

Let me explain my reasoning.
The engine, historically, needs assistance to start. Even before this perceived valve problem.
Be it bore sealant or "easy start" ? Since time imemorial the technique has been used by skilled engineers to assess compression loss.
Freeing a sticky valve is not going to solve the historical problems.
Not to address the underlying problems is a short time botch.

I am focussing on the actual question that the OP is asking.

The owner of the engine seemed to be happy with the fact that the engine needed "easy start" for the first start of the day and apparently wishes to restore the situation to the one that prevailed before the period of non-use.

As a half a century of experience engineer, I'm perfectly well aware that the engine obviously had pre-existing compression/combustion issues. However the issue being raised by the OP is why the previous starting procedure is not longer doing the trick and why oil is now being ejected from the air inlet and that is the issue that I and several others are addressing.

If it were my engine would I have taken off the head? Yes, probably years ago ..... but there may be many reasons why the owner of the engine does not wish to do the same and we are providing the potentially simplest solution to his current predicament, as expressed in the OP.

Richard

 

[kieronriley]

Hope I can get a photo on but if not I’ll explain first then try and download a photo. A previous owner has made an air filter with some sort of mesh wrapped around the old conical metal frame . When I took the head off I was staggered to find two fairly big pieces of black crap under the inlet valve holding it open , I removed the valve and cleaned the stuff away then then cleaned the valve ( I will lap it in just in case) it’s now spotless, and I’m sure that when reassembled it will start and run perfect.(I did also remove the exhaust valve and found that to be spotless as well bus as with the inlet valve I will lap it in just to be sure ) so thanks for all the comments and help . And the lesson is
DONT MAKE A MAKE SHIFT AIR FILTER

 

[black mercury]

While the head is off you could check for a bent con rod. With the piston at the top of it's stroke the piston crown should be slightly above the level of the block face.

 

[179580]

Hope I can get a photo on but if not I’ll explain first then try and download a photo. A previous owner has made an air filter with some sort of mesh wrapped around the old conical metal frame . When I took the head off I was staggered to find two fairly big pieces of black crap under the inlet valve holding it open , I removed the valve and cleaned the stuff away then then cleaned the valve ( I will lap it in just in case) it’s now spotless, and I’m sure that when reassembled it will start and run perfect.(I did also remove the exhaust valve and found that to be spotless as well bus as with the inlet valve I will lap it in just to be sure ) so thanks for all the comments and help . And the lesson is
DONT MAKE A MAKE SHIFT AIR FILTER

Don't blame the previous owner. Yanmar 128171-12540 fit the bill? Notorious for disintegrating.

 

[vas]

I'd never have thought of such a thing happening tbh!
as Tamarside says, that looks like bits that fell off the stock yanmar filter inner metal mesh. IIRC it's around 20euro, a new one and you're good to go...

V.

 

[JumbleDuck]

While the head is off you could check for a bent con rod. With the piston at the top of it's stroke the piston crown should be slightly above the level of the block face.

You could also look for the crack across the exhaust valve seat.

 

[andsarkit]

Don't blame the previous owner. Yanmar 128171-12540 fit the bill? Notorious for disintegrating.

I was quite surprised to find that my air filter has also completely disintegrated and had presumably passed though the engine. Another GM10 I looked at was exactly the same. I was unwilling to pay Yanmar prices for another one which would fail again, so got some air filter material from a motorsport place on ebay. It was easy enough to make a suitable cone shape using a ruler and compasses and glue the join. I am hoping that this will last much longer and not cause further ingestion of the foam.

 

[179580]

I was quite surprised to find that my air filter has also completely disintegrated and had presumably passed though the engine. Another GM10 I looked at was exactly the same. I was unwilling to pay Yanmar prices for another one which would fail again, so got some air filter material from a motorsport place on ebay. It was easy enough to make a suitable cone shape using a ruler and compasses and glue the join. I am hoping that this will last much longer and not cause further ingestion of the foam.

Or buy a suitable sized K&N.

 

[Buck Turgidson]

Or buy a suitable sized K&N.

In bubblegum pink anodised. You can then claim a 5hp increase in power with immunity