Export thread

I have an older B&S 18.5 ohv engine that had a couple of issues mainly camshft so while i was in there I decided to replace the rings because of low compression. the cylinder wall and piston were not scared up so i honed the cylinder for a few seconds cleaned everything put new rings in, new camshaft, tappets, new crankshaft seals, made sure oil slinger was good and new sump gasket. while head was off I took it apart and cleaned everything and made sure the valves closed good. Installed a new head gasket. Put it all back together and adjusted valves. Engine started and ran great but started to smoke so I went to muffler where it was coming from and could see the oil leaking out of the muffler. Took valve cover off and there was alot of oil in it. took head back off and there was not alot of oil in the cylinder. Put head back on and tried again. still pushing oil out the exhaust. Any ideas of problem? Thanks guys for any help.

(Update) (7-11) After several pieces of advice, I put everything back together and but I unhooked breather hose from the carb and started the engine. The muffler started smoking some after it ran a few seconds and began to ease off as the residue oil on it was burning off. I let it run a few minutes and idled it down every minute or so until it was at a low idle and it began to act up then cut off. Probably carb. But I checked the muffler and it was not leaking oil out of it like before. Checked oil level after a couple of minutes and it was at same mark as before it was run. So the pushing oil out of the muffler stop by pulling the breather valve hose off the carb. Question now is how to fix that so it works right? Thanks guys for the help so far. Engine---31N707-0301-B1,, MD- 090514ZA.

Most likely some oil has seeped into the muffler when you were working on the engine
Cut the grass a few times & see if it clears up
If not pull the breather tube off the air box
Problem goes away = head gasket leaking / breather valve malfunctioning .
Rocker cover should have oil in there .

Wonder if the block has a crack allowing oil into the exhaust port then into the muffler? As in never cleaned the cylinder cooling fins?? Shot in the dark.

If you just put new rings in, you need to allow them to seat. It's going to smoke a while. Shouldn't have oil running out of the muffler.

Your low compression might of been a simple valve adjustment, valve guide moved or a stuck open valve.

slomo

Thanks for the info. Valve cover does usually have some oil in it when you pull it off but this time i pulled the cover off pulling the top back then the bottom. there was about half the depth of the cover of oil in it. Never seen that much oil in the valve area before and that doesn't include that , that spilled taking it off. Also i cleaned the muffler out afetr the first leak and let it dry. Second time you could see the oil coming out of the seams of the muffler. I will check the breather tube and see what is going on there. Thanks.

slomo said:

Wonder if the block has a crack allowing oil into the exhaust port then into the muffler? As in never cleaned the cylinder cooling fins?? Shot in the dark.

If you just put new rings in, you need to allow them to seat. It's going to smoke a while. Shouldn't have oil running out of the muffler.

Your low compression might of been a simple valve adjustment, valve guide moved or a stuck open valve.

slomo

Click to expand...

I clean engine before working on it . Everything. as to not get dirt inside of engine while working on it. Once back together i adjusted valves to B&S settings.(manual). I also adjusted valves before working on engine and didn't help the compression. its smoking because of the oil in muffler not because of the rings. Thanks for your info.

Oil level exactly on the full mark? Not over or under?

Does the oil smell like gas? Smell the dipstick.

When checking the oil, screw the dipstick all the way in then remove and check level. Some engines like Kawasaki's and Honda's you park the stick on top of the threads only. Check your engine manual to be sure.

I like Bert's idea of checking the breather hose while running. Post up a video here with the breather hose off and engine on.

slomo

bertsmobile1 said:

Most likely some oil has seeped into the muffler when you were working on the engine
Cut the grass a few times & see if it clears up
If not pull the breather tube off the air box
Problem goes away = head gasket leaking / breather valve malfunctioning .
Rocker cover should have oil in there .

Click to expand...

I pulled the breather reed tube off the carb and started engine. It ran good at higher rpms and didnt push oil out of the muffler but when I run it at low speed it strated running crappy and finally shut off. I guess I need to check the breather reed chamber and clean everything replace the Reed and try it again and see if that cures it.

Being a 31 cu in series I would put odds on a blown head gasket as they are known for this happening between the cylinder and the push rod galley. If you have access to a leak down tester. Remove the valve cover and dpi stick while testing listen at the air escaping it would louder at the push rod galley if the head gasket is blown.

StarTech said:

Being a 31 cu in series I would put odds on a blown head gasket as they are known for this happening between the cylinder and the push rod galley. If you have access to a leak down tester. Remove the valve cover and dpi stick while testing listen at the air escaping it would louder at the push rod galley if the head gasket is blown.

Click to expand...

Thanks. I just put a NEW Head Gasket in it then I discontected the breather hose from the carb and started it up. It ran good at higher rpms and it stoped pushing oil out of the muffler, but when I idled it down to slow rpms it started acting up and then eventually shut off. I will do some checking of the breather reed system and see if it is clogged or reed is messed up. Thanks again.

I regularly have to dress the head & the block because they errode where the gasket is blown.
Did you check both for square & for hollows with a strait edge before you replaced the gasket.
It would not be the first time a brand new gasket failed in service.

bertsmobile1 said:

I regularly have to dress the head & the block because they errode where the gasket is blown.
Did you check both for square & for hollows with a strait edge before you replaced the gasket.
It would not be the first time a brand new gasket failed in service.

Click to expand...

Good point as the next to last head gasket replacement I found the head with a .005" warpage at the blown area.

And doing leak down before and after is just an extra non-invasive measure to verify things.

bertsmobile1 said:

I regularly have to dress the head & the block because they errode where the gasket is blown.
Did you check both for square & for hollows with a strait edge before you replaced the gasket.
It would not be the first time a brand new gasket failed in service.

Click to expand...

Thanks. I will double check that.

StarTech said:

Good point as the next to last head gasket replacement I found the head with a .005" warpage at the blown area.

And doing leak down before and after is just an extra non-invasive measure to verify things.

Click to expand...

Thanks for the info. So why would the oil stop pushing out the muffler when i disconect the breather reed hose from the carb?

slomo said:

Oil level exactly on the full mark? Not over or under?
Does the oil smell like gas? Smell the dipstick.

Click to expand...

It seems you never answered this question, but it is extremely important.

Gasoline can migrate into the oil, dilute the lubrication capability, and end up destroying your engine.

Born2Mow said:

It seems you never answered this question, but it is extremely important.

Gasoline can migrate into the oil, dilute the lubrication capability, and end up destroying your engine.

Click to expand...

There is no gas in the oil. Never was. I have had that issue before so i always smell the oil and check fuel level. The oil level never went up, as it would if fuel was going through cylinder into the the sump cover. The oil level would start at just above the halfway point and end up at the add oil bottom mark after running a few minutes. Thanks.

Bat57 said:

There is no gas in the oil. Never was. I have had that issue before so i always smell the oil and check fuel level. The oil level never went up, as it would if fuel was going through cylinder into the the sump cover. The oil level would start at just above the halfway point and end up at the add oil bottom mark after running a few minutes. Thanks.

Click to expand...

You need to get into the habit of topping off the oil exactly on the full mark prior to every mow.

No fuel in the gas, good to know.

slomo

You guys need to go to a glass shop. Get a 1/2" thick, 12" x 16" piece of plate glass. Lay some wet/dry sand paper on it. This is how I true up parts now. Let the paper do all the work. Don't try to press down to help. You will make the part uneven doing that. Great for cylinder heads and those old pulsa-jet carb flanges.

slomo

Bat57 said:

Thanks for the info. So why would the oil stop pushing out the muffler when i disconect the breather reed hose from the carb?

Click to expand...

Your oil sump slash breather system is pretty cool. The breather is a ONE WAY, pressurized air OUT of the engine pipe to the air filter. The breather keeps a small vacuum on the oil sump limiting oil pooling at the rings. This help with oil consumption. Your oil dipstick tube should have an O-ring or gasket. This is to SEAL the tube to keep the vacuum IN the oil sump. The breather should have a small restriction to limit oil flow OUT of the breather tube into the air filter box. Probably some foam in there too to catch oil vapors and return to the sump.

I would check your dipstick tube for a proper gasket. Clean the threads off. Probably a ton of oil and grit around there.

Next I would check or replace your breather system all the way to the carb. You said this was an old engine. Might have an oil/grit/dirt plug in it some where causing it to not work.

Lastly did you end gap check and set your rings? Did you measure the bore before and after the hone job? Is your cylinder even round?

So if everything above it tip top, sounds like the rings didn't seat. Must have a ton of blow-by.

slomo

Bat57 said:

Thanks for the info. So why would the oil stop pushing out the muffler when i disconect the breather reed hose from the carb?

Click to expand...

Oil gets into the engine from 3 sources
1) past the rings
2) down the intake valve guide
3) through the carb via the breather

The driving force for this excessive pressure in the crankcase .
So in your case the breather is restricting the flow of crankcase gasses and the oil is blowing out the breather then into the engine via the carb

slomo said:

Your oil sump slash breather system is pretty cool. The breather is a ONE WAY, pressurized air OUT of the engine pipe to the air filter. The breather keeps a small vacuum on the oil sump limiting oil pooling at the rings. This help with oil consumption. Your oil dipstick tube should have an O-ring or gasket. This is to SEAL the tube to keep the vacuum IN the oil sump. The breather should have a small restriction to limit oil flow OUT of the breather tube into the air filter box. Probably some foam in there too to catch oil vapors and return to the sump.

I would check your dipstick tube for a proper gasket. Clean the threads off. Probably a ton of oil and grit around there.

Next I would check or replace your breather system all the way to the carb. You said this was an old engine. Might have an oil/grit/dirt plug in it some where causing it to not work.

Lastly did you end gap check and set your rings? Did you measure the bore before and after the hone job? Is your cylinder even round?

So if everything above it tip top, sounds like the rings didn't seat. Must have a ton of blow-by.

slomo

Click to expand...

Thanks for the Information, I will check these things.

bertsmobile1 said:

Oil gets into the engine from 3 sources
1) past the rings
2) down the intake valve guide
3) through the carb via the breather

The driving force for this excessive pressure in the crankcase .
So in your case the breather is restricting the flow of crankcase gasses and the oil is blowing out the breather then into the engine via the carb

Click to expand...

Thanks I will check this out.