# Honda GX390 : Spark plug covered in oil + no compression?



## hend1x (Sep 1, 2017)

Hello everyone,
I picked up a used snowblower and its been giving me headaches. Where it sits now is it runs good until the spark plug gets covered in oil and it runs like junk. The source of at least some of the oil is from the valve cover sending oil into the air box. I don't know if it is all of it but I definitely notice enough to be dripping out of the air box / on the carb.

I pulled out the compression tester and its is goes up to like 5 or 10 then back to 0 every stroke. Any idea how it is possible that the engine runs good when I put a clean spark plug in it? Seems like maybe my compression tester is mixed up or the gx390 pressure release system is kicking in...

I'm stumped...I would appreciate any input.


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## BeerGhost (Dec 17, 2013)

Does the oil smell like gas?


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## hend1x (Sep 1, 2017)

I just changed it this morning. No gas smell, it smelt really cooked even though I changed it about 3 hours ago.


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## orangputeh (Nov 24, 2016)

The first thing i would do is put machine and check oil level. pull stick and if it overflows it is overfilled.

compression tester may be bad. access to another?

leak down test next. ( if it runs )


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## hend1x (Sep 1, 2017)

Not overfilled. When I first got it I changed it. Just changed the oil this morning after 3 hours of use. I double checked, it looks good.

I should clarify, after I changed the oil I ran the machine for another 30 minutes and the spark plug was completely covered in fresh oil (I cleaned it because it was super crusty) before.

I assume the guy that sold this to me was a scammer...I just need to know how to handle things from here.


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## Big Ed (Feb 10, 2013)

Maybe the oil is getting in your combustion chamber through the rings or valves?


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## orangputeh (Nov 24, 2016)

sounds like needs top end rebuild at the very least. 
it must be smoking.


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## hend1x (Sep 1, 2017)

Every now and then it does a puff but not really smoking at all. I don't get it...the thing runs/sounds good when the spark plug is clean.


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## Shovel (Mar 26, 2019)

It seems like it would be visibly smoking if its smoking enough to foul the plug. 
Are you sure its oil fouling and not fuel fouling. 
How long does it take to warm the engine to be able turn off the choke?..If its not taking a minute or two to be able to run without the choke and have no surging..its rich.


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## hend1x (Sep 1, 2017)

How interesting. So you are spot on about being able to run without the choke, I instantly turn it off no problem at all. I didn't think anything of it. So maybe it fuel, I'm not sure...it looked thick like oil but maybe I was mistaken.

I was discussing with a mechanic earlier today and I learned some more information. Apparently I am suffering from blowback. The tube that connects my valve cover is pushing oil into my air box. We don't know why its happening, he said probably ring failure but isn't sure.

I'm not really sure what to make of this mess honestly. I guess I'm gonna park it until spring...pull of the head and take it from there. Maybe the thing is still salvagable. Stinks because we have more snow coming tomorrow and I bought this machine because the bolens tractor/snowblower combo I got ready for this winter could not throw snow properly (single stage) and had horrible traction (only 400 lb machine)...what a mess...can't wait for spring.


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## Shovel (Mar 26, 2019)

Sounds like your carb is overflowing with fuel..possibly some debris on the needle valve.
If you get gas in your oil...you are more apt to end up with oil spray coming out of the tube as the oil will be thinner ..as more oil ends up in the valve cover area.

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## ST1100A (Feb 7, 2015)

You could have a bad 'Breather Filter' or a bad breather check valve in your valve cover that needs to be replaced, it could be letting a lot of oil into your air filter intake tube that gets sucked into your carburetor, then into the combustion chamber, then you would have to replace the valve cover if you would have that type of breather.
Most Honda snowblowers don't use that set-up. The breather hose is vented to outside air and not into the engine air intake like the regular industrial engines would be.
It could have clogged 'Drain back' holes in the engine not allowing the oil to drain back to the crankcase, and flooding the upper head with oil if it has that type breather.
Another thing that can cause excessive oil 'Blow By' is using oil that is too thin or too low a viscosity besides having worn internal parts like valve guides or piston rings.
A bad breather valve can also cause excessive 'Blow By' contamination resulting in excess pressure build-up in the crankcase that would force oil past the rings and valve guides and into the combustion chamber.
The job of the breather is to keep air out of the crankcase so it doesn't build up pressure causing oil blow by. If the breather is not functioning properly or clogged, pressure builds up in the crankcase and you will have oil leaks somewhere, either externally or internally like you are describing.


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## ST1100A (Feb 7, 2015)

You wonder if somebody decided to 'Enlarge' the main jet by 'Reaming/Drilling' it and took out the built in 'Venturi' of it to make it '****' fuel into the carburetor so much that it is 'Wet Fouling' everything.
Once the excess gasoline combines with the carbon in the combustion chamber, it will look like oil, and if the engine runs, it will usually smoke black. 
Oil smoke is normally a greyish blueish color, not blackish.
The OP didn.t mention much about any 'Smoke' or the color, because an oil leak problem normally smokes a lot more than a 'Rich' fuel problem will.


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## orangputeh (Nov 24, 2016)

ST1100A said:


> You wonder if somebody decided to 'Enlarge' the main jet by 'Reaming/Drilling' it and took out the built in 'Venturi' of it to make it '****' fuel into the carburetor so much that it is 'Wet Fouling' everything.
> Once the excess gasoline combines with the carbon in the combustion chamber, it will look like oil, and if the engine runs, it will usually smoke black.
> Oil smoke is normally a greyish blueish color, not blackish.
> The OP didn.t mention much about any 'Smoke' or the color, because an oil leak problem normally smokes a lot more than a 'Rich' fuel problem will.


very good points. I was a little puzzled that it didnt smoke much if the plug was oil soaked. gas makes more sense.

plus the breather issue. I usually ask people to check that rubber tube for blockage. didnt think of the valve cover vent. good catch. That would explain excess crankcase pressure.

I dont know why that breather tube goes into the airbox when other HS models don't do that. on the 622 that airbox hole is plugged and sometimes that causes excess crankcase pressure and oil leaks as mentioned in previous topics.

The owner removed plug and no more oil leaks.

not sure if mentioned but would also check oil for gas smell and overflowing pointing to problem with float and/or needle valve etc.


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## ST1100A (Feb 7, 2015)

orangputeh said:


> very good points. I was a little puzzled that it didnt smoke much if the plug was oil soaked. gas makes more sense.
> 
> plus the breather issue. I usually ask people to check that rubber tube for blockage. didnt think of the valve cover vent. good catch. That would explain excess crankcase pressure.
> 
> ...


It only mentions the engine in his post, not what snowblower it is on, if it is even on a snowblower.
I read somewhere about gas smell in the oil to point out a needle and seat/ float problem, that is what happens when you forget to turn off the fuel valve when the engine is not in use.
I came across breather vent problems with a lot of Kohler engines and some Briggs, usually older ones.
The Kohler's had the 'Check Valves' go bad and the little 'Mesh' screens that separate the oil from the air deteriorate and fall apart to nothing, letting raw oil blow out. Some of the Kohlers were 'Rebuildable' with all the little parts available for replacement. Some Briggs have a spring that pushes back a reed valve disc and the spring gets weak or breaks. On those you have to replace the whole breather cover.
The OP could have a machine that was a custom build and not have the original engine, that's a good question.
On the HS622 you mentioned, if the breather hose was connected to the plugged off nipple for the hose on the air box, that will cause problems like oil leaks and smoking.


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## Big Ed (Feb 10, 2013)

ST1100A said:


> It only mentions the engine in his post, not what snowblower it is on, if it is even on a snowblower.


It is in the title?
*Honda GX390 : Spark plug covered in oil + no compression?*


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## groomerz (Feb 7, 2015)

Loose main jet?


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## ST1100A (Feb 7, 2015)

groomerz said:


> Loose main jet?
> 
> 
> Sent from my iPhone using Tapatalk


A possibility. It would usually flood itself out right away if that happened.


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## ST1100A (Feb 7, 2015)

Big Ed said:


> It is in the title?
> *Honda GX390 : Spark plug covered in oil + no compression?*


You have to wonder what it is on.
Honda does not hook the breather tube to the intake pipe of the carburetor to the air-box on snowblowers like he mentioned, so it shouldn't get oil in the air-box.
It could be a replacement engine that is not normally used on a snowblower.
Honda snowblower engines vent the pipe to outside air, like a 'Road Draft Tube' on old cars before emissions took effect on the new cars, that was before 'PCV' valves were heard of.
The only Honda that used the GX 390 was the 1300 series blowers in the USA.


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## Big Ed (Feb 10, 2013)

ST1100A said:


> You have to wonder what it is on.
> Honda does not hook the breather tube to the intake pipe of the carburetor to the air-box on snowblowers like he mentioned, so it shouldn't get oil in the air-box.
> It could be a replacement engine that is not normally used on a snowblower.
> Honda snowblower engines vent the pipe to outside air, like a 'Road Draft Tube' on old cars before emissions took effect on the new cars, that was before 'PCV' valves were heard of.
> The only Honda that used the GX 390 was the 1300 series blowers in the USA.


OK, then I guess an engine number would help?
Hend1x, do you have an engine number?

Or is GX 390 the engine number?


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## 140278 (Aug 27, 2020)

he has another thread listing a craftsman Used Craftsman II 8/25 Trac drive : Get ready for winter


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## ST1100A (Feb 7, 2015)

The 'GX 390' is the engine family, he will need the whole engine number stamped on the block, and also get the model numbers an serial numbers off of the frame of the snowblower.
Tabora can match all of the numbers and see if it is the proper engine for the snowblower.


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## ST1100A (Feb 7, 2015)

captchas said:


> he has another thread listing a craftsman Used Craftsman II 8/25 Trac drive : Get ready for winter


Wow! I saw the older post.
Maybe he isn't sure what he has, it could be something somebody 'Pieced' together.


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## orangputeh (Nov 24, 2016)

Big Ed said:


> OK, then I guess an engine number would help?
> Hend1x, do you have an engine number?
> 
> Or is GX 390 the engine number?


gx390 is a 13 horse Honda engine. seen a lot of these on pressure washers. they also have real air filter elements in them. talk about carb problems on pressure washers.........geesus meenusus.


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## Big Ed (Feb 10, 2013)

OK, I guess that I should have shut up after my post #6.


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## orangputeh (Nov 24, 2016)

Big Ed said:


> OK, I guess that I should have shut up after my post #6.


after reading my post I think you took itin the wrong way? I was just meaning there are a ton of carb problems on Honda pressure washer carbs. lots more dirt , dust , dirty water etc..

we cool?


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## Big Ed (Feb 10, 2013)

orangputeh said:


> after reading my post I think you took itin the wrong way? I was just meaning there are a ton of carb problems on Honda pressure washer carbs. lots more dirt , dust , dirty water etc..
> 
> we cool?


Yeah, I am good, that was not directed towards anyone but ME. 
I never had a Honda, I didn't even know that the GX 390 was an engine number. I thought it was a model number.
What I posted in post 6 is OK, but I should have stopped there an let the Honda guys do their thing.

I will stick with Craftsman and Snowbirds or similar machines.
Unless I get a Honda.


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## orangputeh (Nov 24, 2016)

Big Ed said:


> Yeah, I am good, that was not directed towards anyone but ME.
> I never had a Honda, I didn't even know that the GX 390 was an engine number. I thought it was a model number.
> What I posted in post 6 is OK, but I should have stopped there an let the Honda guys do their thing.
> 
> ...


boy we are on the wrong page here....

that post wasnt directed towards you ( the jeesus meneezus comment ) anyways.

gx390 is really not the engine number. its just the size. approx cc displacement.


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## Big Ed (Feb 10, 2013)

orangputeh said:


> boy we are on the wrong page here....
> 
> that post wasnt directed towards you ( the jeesus meneezus comment ) anyways.
> 
> gx390 is really not the engine number. its just the size. approx cc displacement.


Now you have confused me. 
All good here.


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## tabora (Mar 1, 2017)

ST1100A said:


> The only Honda that used the GX 390 was the 1300 series blowers in the USA.


And the EU6500 & EU7000 generators and WT40 pump...


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## ST1100A (Feb 7, 2015)

tabora said:


> And the EU6500 & EU7000 generators and WT40 pump...


And the EG, EB 6500 generators, some tillers and mowers and many other Honda products.
I just listed the Honda snowblowers it was used on since it was mentioned on the snowblower forum.


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## badbmwbrad (Jul 30, 2019)

Your engine may have a compression release mechanism which affects exhaust valve operation. Look inside the carburetor to verify proper assembly.

I recently resolved a problem inside a carburetor which had been improperly reassembled such that the main jet would fall out of its correct location and land in the bottom of the float bowl. Prior to resolution, the engine would start up but would run very rough and spew clouds of blue smoke.


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## 140278 (Aug 27, 2020)

used machine no brand listed, only that it has a honda motor, that seems to be pumping a lot of oil, he seems to grab and flip 
his last log in reads the day of the first post , so how about we take a coffee break and wait till he logs back in with more information ?


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## ST1100A (Feb 7, 2015)

On the snowblower engines the breather tube hangs loose, it just aims down from where it mounts in the valve cover.
The Honda snowblowers and most other snowblowers do not use an air filter element because they would freeze up with ice when running in cold weather, plus there isn't much dust and debris around them when in operation.
Honda air boxes have 'Swirls' built into them to help 'centrifugally' toss pieces of dirt away from the air intake going to the carburetor.
That is why the snowblower engines are 'jetted' a little bit richer than the standard industrial engines, not only because of running in colder temperatures, but from lack of restriction due to no air filter element.


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## orangputeh (Nov 24, 2016)

Rooskie said:


> I am having difficulty determining what the breather hose is supposed to be connected to on my 622. The parts diagrams don't show that.
> Does it hang loose?
> I also discovered no air filter element in the air cleaner. I was surprised to see it was supposed to have one.
> Might that cause a problem in the carburetor air/fuel mix?


you shouldnt hijack threads as this will confuse everyone. start your own thread about your topic . i'm not a mod but this is a continuing frustrating problem here. I'm guilty of this myself . It just confuses people .


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## 140278 (Aug 27, 2020)

that post has been moved into his own thread


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