FG110 GX25 - too much oil out of breather!

[mr.farmall]

Honda tiller FG1100K1AT with GX25 engine. 4 cycle miniature tiller on the line of a mantis tiller, a very good machine! The problem is that oil comes out of breather tube into carburetor intake while engine is running. It saturates the breather element and drips out the bottom onto the tiller shroud.
After taking the valve cover off and finding it with a lot of oil in it, I cleaned it out to determine the flow of the oil and why it puts a couple drops out the breather tube every minute.
It appears that oil is pumped up to the valves and enters a plastic distributor of some sort found in the valve cover. The distributor has 5 exit holes that I found; one on each end out of the distributor and three hard plastic tubes incorporated into the distributor with exit holes. One pointing toward the engine and the other two pointing the opposite direction. It appears that the sealed chamber this distributor sits in fills with oil for lubrication of the valves and then returns the oil to the engine through a square shaped hole near the top of the chamber. The problem I see is that the breather hole is lower than the return port to the engine body.
There is a maze the oil must travel through and a metal filter that can pass oil into or out of the chamber on the path to reach the breather port leading to the carburetor. It seems that with the return port higher than the breather port, the oil finds it's way out of the breather exit hole into the carburetor.
This must be confusing to some one not familiar with this engine, and I must certainly be missing something, but could some one please explain how this is to work and why I am getting so much oil into the carburetor via the breather?
The engine starts well and seems to run OK, but with only holding about 2 1/2 oz of oil, it won't take long to remove this small amount of oil through the breather hole! Resulting, of course, with a constant need to check and fill the oil and the tiller getting coated with oil and dirt grime because of this.
The oil is checked on a dipstick after the engine has been rotated 90 degrees from it's normal working stance to it's storage stance (sort of on it's face). Too much oil will just run out the filler hole when sitting this way. not allowing it to be over filled.
Could it be that blow by pressure is forcing the oil out of the engine due to wear? this unit hasn't been used very much.
Any help would certainly be very much appreciated.
Rex

 

[mr.farmall]

Honda tiller FG1100K1AT with GX25 engine.

Could it be that blow by pressure is forcing the oil out of the engine due to wear? this unit hasn't been used very much.
QUOTE]
This morning I tried a leak down test but I had no fittings that will fit the extremely small hole of the spark plug. ( about 1/4 inch or so) But I was able to get a rubber tipped pressure gauge over the plug hole and check the compression. It is very low, about 20psi. I don't know this engine enough to know if it has compression release built into it or not, nor do I know what the compression pressure should be. If their is anyone out there that could help or had any theories of what is happening here , I would certainly appreciate it.
Rex
I found some specs on Honda's website. This engine does have an exhaust compression release on it

 

[robert@honda]

Sure reads like "dirt ingestion / rapid cylinder wear" to me.

Could be carbon build-up on the valves, but unlikely. Same goes for the timing belt being a tooth or two off. Could, and has happened, but rare.

On the GX25, in a tiller application, the air filter must be kept up carefully. You can pull the carburetor and shine a flashlight down into the engine, and look for traces of dirt. That, and a genuine compression test, will pretty much confirm you've got a worn-out cylinder. The compression spec is 131-159 psi @ 2,000 rpm.

A leak-down test would also pretty much confirm too.

 

[mr.farmall]

Sure reads like "dirt ingestion / rapid cylinder wear" to me.

Could be carbon build-up on the valves, but unlikely. Same goes for the timing belt being a tooth or two off. Could, and has happened, but rare.

I'm glad you replied, I've read a lot of your post and thought you might be the one that would have some good info.

A leak-down test would also pretty much confirm too.

I made a threaded tube to fit the spark plug hole and the leak down tester. with this, the leak down test showed we have 70 % leak down losses at the best location. I can hear pressure on the intake coming out of the intake side.
[/QUOTE]

a genuine compression test, will pretty much confirm you've got a worn-out cylinder. The compression spec is 131-159 psi @ 2,000 rpm.

Using a compression gauge, I can only get 18 PSI. this is by bulling the pull rope as rapidly as I can, not at the 2000 rpm you have stated.
I am surprise with the very pour results that it will even run, but it seems to run well. It both runs at high speed and at idle. It takes priming and choking both to get it started and then a minute to get it warmed up before you can remove the choke. After that, it runs pretty good, but the air filter just fills right back up with oil coming from the breather after only about 1/2 hour.
What are your thoughts?
Rex

 

[robert@honda]

I'm glad you replied, I've read a lot of your post and thought you might be the one that would have some good info.
I made a threaded tube to fit the spark plug hole and the leak down tester. with this, the leak down test showed we have 70 % leak down losses at the best location. I can hear pressure on the intake coming out of the intake side.

Using a compression gauge, I can only get 18 PSI. this is by bulling the pull rope as rapidly as I can, not at the 2000 rpm you have stated.
I am surprise with the very pour results that it will even run, but it seems to run well. It both runs at high speed and at idle. It takes priming and choking both to get it started and then a minute to get it warmed up before you can remove the choke. After that, it runs pretty good, but the air filter just fills right back up with oil coming from the breather after only about 1/2 hour.
What are your thoughts?
Rex

Are you getting any smoke from the exhaust?

When you rev up the engine and let the tines dig in, is there a loss of power/guts?

A quick yank on the recoil should get you about 2,000 rpm (briefly). Our tech guys tell me that's why it is spec'ed at that number in the shop manual.

The engine is an easy tear-down for inspection, but for the time and cost of parts, usually not economical to repair or rebuild. A brand new engine is about $275, while an entire tiller (Honda's FG110) is $349, with a new warranty, etc.

FYI, the oil distribution is quite clever; oil is churned into a mist by a twin-bladed oil slinger on the end of the crankshaft, and the atomized oil/air mixture is then "pumped" to all parts of the engine. The first application for the engine was on string trimmer, so there had to be a way to insure lubrication regardless of the engine position and the effects of gravity on the oil. While more complex and heavier than a 2-stroke, the 4-stroke Honda is smoother, can deliver torque at lower speeds, doesn't smoke, and uses regular unleaded.

Here's a page from an older model, the GX22, but I think the GX25 is the same design:

 

[mr.farmall]

A quick yank on the recoil should get you about 2,000 rpm (briefly). Our tech guys tell me that's why it is spec'ed at that number in the shop manual.

The engine is an easy tear-down for inspection, but for the time and cost of parts, usually not economical to repair or rebuild. A brand new engine is about $275, while an entire tiller (Honda's FG110) is $349, with a new warranty, etc.

FYI, the oil distribution is quite clever; oil is churned into a mist by a twin-bladed oil slinger on the end of the crankshaft, and the atomized oil/air mixture is then "pumped" to all parts of the engine. The first application for the engine was on string trimmer, so there had to be a way to insure lubrication regardless of the engine position and the effects of gravity on the oil. While more complex and heavier than a 2-stroke, the 4-stroke Honda is smoother, can deliver torque at lower speeds, doesn't smoke, and uses regular unleaded.

Thanks soooo much for all the info. It bothers me to have a question that I can't answer and you description of the oil flow makes a confusing system very logical, thus answering the question. I had everything flowing backwards as and oil instead of flowing the correct direction first as a mist and then returning as an oil. What I thought was a port that delivered the oil to the rocker shafts is actually the return port! How clever? That's why it's lower than the breather tube.
It's too late and dark to give the tiller a try under load, but I will report back once I cat get it done.
As I think about your comments of the reed check valve stopping the vacuum from reaching the valve area, I wonder if that could possibly be allowing a pressure difference that forces the oil out of the breather tube? Just a thought!
Thanks again
Rex

 

[clay45]

A dirty filter will cause oil to be pulled into it. Install new filters and see if problem persists.

 

[mr.farmall]

A dirty filter will cause oil to be pulled into it. Install new filters and see if problem persists.

As you probably already know, the filter on this little gem is an oil foam filter. it cleans up nicely and then is re oiled and re-positioned on the engine. It's after the engine starts that the trouble also starts, the engine continues to re oil it with copious amounts of oil (a drop or two every minute), coming from the breather. after a half hour, it can output a table spoon or so! It only holds 2.5 oz.-- at 3 tablespoons per oz = it holds about 8 table spoons. using 1 tablespoon in 1/2 hour, can totally deplete the oil in 4 hours use. Of coarse the engine would seize sooner than that from lack of oil.
This is the dilemma.
Thanks for your reply.

 

[bertsmobile1]

Thanks soooo much for all the info. It bothers me to have a question that I can't answer and you description of the oil flow makes a confusing system very logical, thus answering the question. I had everything flowing backwards as and oil instead of flowing the correct direction first as a mist and then returning as an oil. What I thought was a port that delivered the oil to the rocker shafts is actually the return port! How clever? That's why it's lower than the breather tube.
It's too late and dark to give the tiller a try under load, but I will report back once I cat get it done.
As I think about your comments of the reed check valve stopping the vacuum from reaching the valve area, I wonder if that could possibly be allowing a pressure difference that forces the oil out of the breather tube? Just a thought!
Thanks again
Rex

Yes,
A faulty reed valve will allow the crank case to fill during the up stroke then there will be too much gas in there on the down stroke.
Worn rings will do the same thing
Cracks or holes in the piston will do the same.
Blown head gasket can do the same thing
wear in the exhaust valve guide can do the same but to a lesser degree.

 

[mr.farmall]

Are you getting any smoke from the exhaust?

No , thier doesn't seem to be any exhasut smoke

When you rev up the engine and let the tines dig in, is there a loss of power/guts?

Surprisingly, it has quite a bit of spunk!

A quick yank on the recoil should get you about 2,000 rpm (briefly). Our tech guys tell me that's why it is spec'ed at that number in the shop manual.

If thats the case, 2000 rpm,s I am really low on compression.
the tiller runs pretty good and tills fairly good. for the price of a new one, I'll just let this one run untill it won't do the job any more and keep my eye on the oil.
thanks for everyones help.