Mower engine - issue found?

[Lee Nowell]

Hi all,

Further to my earlier posts on my mower engine troubles.... I have now stripped the engine back down and removed the snapped head bolt.

When I fired her up after the previous "fix", it gave out a blast of black smoke at initial start up otherwise run fine but with the odd "cough" and now visible smoke. I let the engine run for around 1 min maybe 2.

Looking at the internals now... I have...

1. a little soot on the plug (was cleaned before fitting before)
2. Black soot on the inlet valve (exhaust valve is clean)
3. A bit of black soot on the piston top (maybe a little oil but difficult to tell)
4. A little oil on the cylinder sides
5. having cleaned the cylinder with a cloth then manually turned the engine over a could of times, there is a little oil again on the cylinder.
6. Checking the oil level, it has been over filled
7. I have removed all sections from fuel tank to inlet valve and all are clean.

So.... a couple of questions.

1. Could the over fill be causing the oil to get past the piston rings or is a little oil normal. I don't think it can be using oil as I haven't added any oil for around 5 years and have been having the issues for at least a year.
2. If the piston ring has gone wouldn't I be seeing a constant flow of black smoke?
3. Could the initial blast of black smoke be crap in the exhaust?

thanks all for your help on this.

Lee.

[Tim]

Overfilling is bad, deal with it. If you didn't overfill it it's remotely possible that diesel has leaked through a split diaphragm in the carb and has diluted the oil.

Whatever, an oil change and refilling to the right level would be a good idea.

Tim

[The Natural Philosopher]

Since when has any lawnmower been diesel or any stock diesel used a carb?

[Tim]

Go back and read the thread from the start. The problems started when the mower was misfueled.

Tim

[Gazz]

"The Natural Philosopher" stood up and shat forth the following:

hey, save those kinds of replies for the resident plonker,

Remember this particular lawnmower had treid to run on diesel, and we all know what diesel does to rubber parts not designed for it.

[The Natural Philosopher]

But any diesel in the fuel would cause smoking throughout the run

[Tim]

Oh for f*ck's sake, do keep up! This was ages ago. There's no diesel in the fuel now.

Tim

[The Natural Philosopher]

Exactly.

[Tim]

Um, meaning I suppose that you still haven't read the thread and haven't a clue?

Tim

[The Natural Philosopher]

No Tim meaning I have read it and the diesel issue was over about 130 posts ago, so I concluded you had simply missed the last 130 posts and actually thought it was a diesel engine.

[Tim+]

Nice try but it's clear that *you* had missed or forgotten the post about diesel misfuelling.

Tim

[robgraham]

's >>> remotely

Sorry NP, but having followed the original thread and this one with interest as my mower engine is misbehaving, I have to come down on Tim's side and say that his 'nice try' comment would seem to be the correct one.

Don't splutter and protest - we all know you just had a brain-fart ! Don't we all on occasions ?

Rob

[Lee Nowell]

tripped the engine back down and removed the snapped head bolt.

st of black smoke at initial start up otherwise run fine but with the odd &= quot;cough" and now visible smoke. I let the engine run for around 1 = min maybe 2.

ne over a could of times, there is a little oil again on the cylinder.

is a little oil normal. I don't think it can be using oil as I haven&#=

39;t added any oil for around 5 years and have been having the issues for a= t least a year.

f black smoke?

To be honest, it could do with an oil change anyway... I guess as NP ment= ions though, even if the oil is thinner and is therefore able to get past t= he piston ring, wouldn't I see black smoke throughout as it would continual= ly burn the thinned oil during operation?

Funnily enough, I was over my brother in-law's yesterday and he has the sam= e engine with the same set of problems....

[Tim+]

Burning oil usually produces white smoke whilst unburnt fuel produces black smoke. They also smell very different.

Tim

[Muddymike]

Hi all,

Not added oil for 5 years!!! You mean you haven't changed it for 5 years!!! Give the poor machine a chance, change the oil.

Mike

[Lee Nowell]

Ah... that is interesting... So the black smoke on initial start is unburn= t fuel which would explain why it is black on initial start post priming. = It still produces a plume of black smoke when started without priming (when= hot) though. After the initial plume, engine runs with no smoke.

thanks

Lee.

[The Natural Philosopher]

black smoke?

More or less exactly wrong. oil is black: over rich is whitish grey.diesel oil also blackish.

[Gary]

fuel which would explain why it is black on initial start post priming. It still produces a plume of black smoke when started without priming (when hot) though. After the initial plume, engine runs with no smoke.

It sounds to me like the engine is not really doing badly now. Black smoke on starting is normal and on a cheap engine, oil smoke is normal until it is warm, expecially with knacked old oil and that could be up to 10 mins. The emissions and regulations and luxury of car engines give a false expectation. Listen to a B reg micra when it is cold and hear it piston slap. The Sunny of the same age will not slap, it is built not to.

In my experience around where I live all small motors take a while to settle down. and you can normally smell them from a couple of gardens away.

The vital question is, can you now use it to mow the grass?

Gary

[Tim+]

??? Never in my experience. Are you still sore about forgetting the diesel misfuelling? ;-)

Seriously though, I'd be interested to read other comments on this. I'll grant you that oil smoke leans towards a bluey grey rather than white but I think you've got it wrong (again).

Tim

[Tim+]

Unless you're still thinking that this is a diesel mower. ;-)

Tim