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I'm mowing last week and have these little dips in my lawn. The mower is having a hard time crawling up the slope, when it used to have no problems at all. Then it starts spewing white smoke out of the muffler.

I pull it into the shop and check the valve adjustment (which has been a chronic problem) - I make a small adjustment, starts right up, but more smoke.

One thing I did notice while adjusting the valves - when the valves were both closed (on the compression stroke), while I hand turn the motor to TDC, I can hear air escaping - I think from the exhaust valve.

Any suggestions how to troubleshoot this further? Then repair?

Thanks,

Nic

May check the head gaskets...leak down test will show it quickly
Darren

Might be worn piston rings. How compression do you have when using a compression tester?

I can do a compression test tomorrow - not sure what the compression should be, but I can at least report back.

Don't have what I need for a leak-down test.

Thanks for the ideas.

Finally had a chance to do the compression test. It was exactly at 50.

Not sure what it's supposed to be - just checked all the manuals I have, nothing mentioned.

Thanks!

Not enough compression. Its supposed to be 100-120.

davbell22602 said:

Not enough compression. Its supposed to be 100-120.

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Wow...I had no idea compression in a small engine was so high.

I removed the cylinder head: there seems to be a little wear/thinning right between the cylinder head and push rod chamber, but it's not broken.

Once I took the cylinder head off, the piston was down, and there was a little oil in the cylinder - I'm hoping it's because the mower is at a slight backward angle and not bad rings. My wife is going to get the gasket tomorrow, I'll button it up and we'll see what we get.

<fingers crossed>

Thank you,

Nic

Well, it's not the head gasket.

I replaced the head gasket, did another compression test - still at 50.

I don't have the resources for a leak-down test.

If the #1 diagnosis is a head gasket, what's the #2 diagnosis?

Thanks,

Nic

Compression readings are useless on these mowers, they have a compression release. Run it and see if the smoking has cleared up. If it has, keep mowing.

Fish said:

Compression readings are useless on these mowers, they have a compression release. Run it and see if the smoking has cleared up. If it has, keep mowing.

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Running out there now!!

<glimmer of hope>

hopefully you will be back in business....

First, the battery was dead and it could barely turn over. Put it on a fast charge for about 10 min and it fired right up.

I spilled a bit of oil on the muffler, so that's burning off, but it didn't belch smoke like it was. As soon as I get the tire pumped up I'll be able to give it a proper shake down cruise. So far, so good.

Thanks Fish!

Nic

Yeah, new rings is rarely the cure. Hope it works good for you.

Fish said:

Yeah, new rings is rarely the cure. Hope it works good for you.

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Unfortunately, the head gasket is not it. I finally got the tire back on, fired it up, and within minutes it started belching smoke again. Lack of power, I engaged the blades and the motor almost quit (like the governor didn't kick in fast enough)...back to the drawing board.

So, what would be next?

In the gasket set I bought, there is a valve stem guide/seal for the intake valve. I'm wondering if the valve stem or the piston rings are the next step (or something else)?

Ideas? Suggestions? (Is there a troubleshooting flow chart I could follow?)

Thanks,

Nic

nplsdvr said:

Unfortunately, the head gasket is not it. I finally got the tire back on, fired it up, and within minutes it started belching smoke again. Lack of power, I engaged the blades and the motor almost quit (like the governor didn't kick in fast enough)...back to the drawing board.

So, what would be next?

In the gasket set I bought, there is a valve stem guide/seal for the intake valve. I'm wondering if the valve stem or the piston rings are the next step (or something else)?

Ideas? Suggestions? (Is there a troubleshooting flow chart I could follow?)

Thanks,

Nic

Click to expand...

Well, the crankcase breather could be plugged, or it may be the valve seal.

Have you made sure that there is no fuel leaking into your oil, causing an overfull condition?

Are you running this with the old oil clogged air filter, if so, it would create great suction and pull oil into the intake.

Did your engine have those little caps on the end of the valves?

Fish said:

Well, the crankcase breather could be plugged, or it may be the valve seal.

Click to expand...

I'll check the breather.

Fish said:

Have you made sure that there is no fuel leaking into your oil, causing an overfull condition?

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How exactly do you "check" that? I had a problem earlier and I replaced the needle in the carb, cleaned the carb and replaced a few gaskets. I was hoping there was nothing wrong with the carb.

Fish said:

Are you running this with the old oil clogged air filter, if so, it would create great suction and pull oil into the intake.

Click to expand...

No, air filter is a little dirty, but it's definitely not clogged. Blow it off with some compressed air and it almost looks brand new.

Fish said:

Did your engine have those little caps on the end of the valves?

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Which "little caps" are you talking about? I saw the valve keepers - is that what you mean?

I'll start by cleaning the breather - it is coated in grime. Trying to figure out why all that dirt/oil/grime is in that area, too.

Thanks,

Nic

If you see dirt sticking on something like that could mean that the gasket is leaky and dirt is adhering to the oil, so the gasket should be replaced,
and while off soak the breather in some solvent or fuel and make sure it is not clogged up.

According to your model/type numbers, the valves had caps on the valve tips which happen to fall out easily and fall down into the crankcase, it is between these caps and the rocker arms that you put your feeler gauges while adjusting valves. I'll see if I can scrounge up one for a pic.

The cap is number 238.


As far as fuel in the oil, the oil will be real thin, smell like gas, etc..

Fish said:

View attachment 17679

The cap is number 238.


As far as fuel in the oil, the oil will be real thin, smell like gas, etc..

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O.k...yes, caps I got.

I think I may have solved the "belching smoke" problem. Pretty sure it was too much oil in the crankcase. I checked and rechecked the levels - and it kept coming up high. So I drained it off, and refilled to proper levels. Hasn't smoked since.

The dirt/oil mixture you're referring to is another story. That deserves some attention, so I'll be troubleshooting it next.

But for now, I'm back to mowing without fogging the entire neighborhood.

Thanks, Fish.

Nic

nplsdvr said:

O.k...yes, caps I got.

I think I may have solved the "belching smoke" problem. Pretty sure it was too much oil in the crankcase. I checked and rechecked the levels - and it kept coming up high. So I drained it off, and refilled to proper levels. Hasn't smoked since.

The dirt/oil mixture you're referring to is another story. That deserves some attention, so I'll be troubleshooting it next.

But for now, I'm back to mowing without fogging the entire neighborhood.

Thanks, Fish.

Nic

Click to expand...

These newer engine's carbs are notorious for leaking a bit while parked, so buying an inline fuel cutoff would be a good investment.