MMO Piston Soak ?

[Quest]

Originally Posted By: Vikas
Restricted exhaust probably sounds most plausible. What is the best way to clean the muffler? I was thinking car cleaner first followed by brake cleaner. Or I would just dunk it overnight in laundry detergent first.

Mechanical problem such as broken valve etc would manifest itself as horrendous noise and/or starting problem, right??

No visible smoke but there are few oil leaks that I have been trying to find. One is the o-ring at the oil filler tube. I tried couple of hardware store o-rings but I might have to bite the bullet and order replacement o-ring from internet.

I have been suspecting lean condition for years and that is why I have dumped really strong dosage of Techron (and similar cleaners) through the gas tank. I would think the internals of that carb would be clean as whistle but I would not know until I take it apart. I would need to order new gaskets etc before going there.


a few suggesitons:

(1)when replacing the O'ring, seals, etc. on these engines, consider getting either proper aftermarket O-rings (viton varieties) or OE Honda.

(2) a proper wet/dry compression test should be able to reveal your compression (wet/dry), your ring sealing conditions, whether you also suffer from significant intake/exhaust valve leaks,etc.

(3) always check the carb (intake) and exhaust muffler (exhaust) gaskets and proper mating conditions. If you have doubt, always consider servicing it properly by pulling carb/muffler out and check mating surfaces, replace with fresh intake/exhaust gaskets and o-rings, etc.

(4) if you suspect that your exhaust has become restrictive due to carbon accumulation, consider dunking it in hot water with detergent, or some kind of solvent bath. Also: if you have a spark-arrest mesh, scrub it with toothbrush or wirebrush to clean it.

Q.

 

[Vikas]

Update:-

The piston soak made no difference. Actually, for some unknown reasons, the clutch started slipping. This Honda has clutch mechanism between the engine and the blade. The blade after running for about 30 seconds started not spinning anymore. In desperation, I put another spark plug. I have no idea why but afterwards I did not have the slippage. Unfortunately, the only way to avoid engine bogging down was to go few feet and let mower catch up its breath.

Later, I took the the muffler off. The hole for the missing stud has stripped threads. However, that is a through hole; so if I can get a larger 6mmx1.0 bolt (at least 120mm) I should be able to put two bolts to secure the muffler. The largest bolt that I found at local hardware or Lowes was limited to 90mm. PLEASE, if anybody know where to find 6mmx1.0-120mm long bolt, let me know.

The exhaust port is oily. What does that mean?

I finally measured the compression. The spec is 58-85. Mine was at 60 :-( The wet compression jumped to 80. Both were taken cold. I also noticed few cracks on the composite deck. Has anybody tried to JB-weld the plastic decks?

There was no spark-arrest mesh. Right now I have the muffler being soaked the Tide detergent and the cylinder with Kreen. I jacked up the front of the mower via a small 2x4 that way, the Kreen should stay inside. I will add more Kreen tomorrow morning and soak for another 8 hours.

I see leaking oil around the deck but can not see the origin. I wonder if the main seal is leaking and is contaminating the clutch disc causing it to slip. I am not able to figure out if there is a way to increase the pressure on the clutch but I doubt that cable adjustment would allow that. I do have the service manual but I do not understand how the clutch mechanism is implemented.

I started to use free after rebate Valvoline Racing Synthetic oil and I suspect that has caused lot more leaks than before. I am going to try ATP-205 and see if that makes a difference. If not, I might have to "buy" some High Mileage oil with real money.

 

[Vikas]

Kreen soak made no difference either :-( Quantitatively, the compression reading remained still the same. Looks like time to try snake remedies such as Restore in the oil.

 

[OVERKILL]

Wet compression at 80, and spec is a max of 85 is FINE. That's not your problem.

The oil in the muffler is from the MMO. You put oil in the cylinder, it is going to end up in the exhaust.

Do you have a propane torch? If so, while it is bogging down, put the (on but unlit) torch to the intake of the carb and see if it speeds up. If it does, she's lean.

 

[JTK]

Originally Posted By: OVERK1LL

Do you have a propane torch? If so, while it is bogging down, put the (on but unlit) torch to the intake of the carb and see if it speeds up. If it does, she's lean.


Isn't it going to rev-up that way regardless of the situation?

I've heard of using propane gas around gasket/sealing areas to see if it revs at some point indicating a leak, but near the carb throat, it's going to perk up every time I'd think.

Joel

 

[OVERKILL]

Originally Posted By: JTK
Originally Posted By: OVERK1LL

Do you have a propane torch? If so, while it is bogging down, put the (on but unlit) torch to the intake of the carb and see if it speeds up. If it does, she's lean.


Isn't it going to rev-up that way regardless of the situation?

I've heard of using propane gas around gasket/sealing areas to see if it revs at some point indicating a leak, but near the carb throat, it's going to perk up every time I'd think.

Joel


Nope. Remember, it is governed to a specific RPM and should be running at or near that RPM during use. This engine is bogging down and NOT operating within that range from what is being described.

If this engine is running at the proper A/F, adding more fuel is going to either:

A) Do nothing of significance
B) Slow the engine down even further because it is excessively rich.

However, if the engine is running too lean, it will respond positively to the added fuel and RPM's will come up.

 

[Vikas]

Is 60psi ok? It is at the low end of the spec. I have to fight out how to spray while it is bogging. If you guys believe compression is good enough I will hold on before going for snake oil. What parts I need to order before taking off the carb on this engine? I think I should be able to handle this

 

[OVERKILL]

Originally Posted By: Vikas
Is 60psi ok? It is at the low end of the spec. I have to fight out how to spray while it is bogging. If you guys believe compression is good enough I will hold on before going for snake oil. What parts I need to order before taking off the carb on this engine? I think I should be able to handle this


60 was dry right? 80 wet? The 80 is the one that matters. Wet readings are the relevant ones.

If you can't figure out how to spray it, maybe rig up some way of delivering an extra zip of fuel into the carb from the controls, like with a squirt bottle, syringe.....etc attached to a piece of clear gas line or the like. The key here is to just add some more fuel and see what it does.

 

[Vikas]

60 dry, 80 weight with the spec being 58-85psi @ 600rpm. I always thought that it is the dry compression that is the relevant one. And large difference between wet and dry signifies weak or worn rings. Am I wrong?

I will rig something to spray the carb cleaner in the throat while it is bogging and see if it recovers. That should confirm the lean running condition, right? I have tried the choke but that only seems to cut the air rather than adding fuel.

 

[OVERKILL]

Originally Posted By: Vikas
60 dry, 80 weight with the spec being 58-85psi @ 600rpm. I always thought that it is the dry compression that is the relevant one. And large difference between wet and dry signifies weak or worn rings. Am I wrong?

I will rig something to spray the carb cleaner in the throat while it is bogging and see if it recovers. That should confirm the lean running condition, right? I have tried the choke but that only seems to cut the air rather than adding fuel.


Dry is useless, wet is the useful reading. The lower dry reading means nothing other than the bore was dry. You are WELL within acceptable at 80, if the spec tops out at 85.

Carb cleaner SHOULD work, though I'd rather use gas or propane.

Yes, choking it cuts off air too, which isn't what you want.

 

[Trav]

Quote:
I finally measured the compression. The spec is 58-85. Mine was at 60 :-( The wet compression jumped to 80. Both were taken cold

Was the throttle wide open, choke off?

 

[JTK]

Originally Posted By: OVERK1LL

If this engine is running at the proper A/F, adding more fuel is going to either:

A) Do nothing of significance
B) Slow the engine down even further because it is excessively rich.


Gotcha.

That does make sense.

Thanks.

 

[OVERKILL]

Originally Posted By: JTK
Originally Posted By: OVERK1LL

If this engine is running at the proper A/F, adding more fuel is going to either:

A) Do nothing of significance
B) Slow the engine down even further because it is excessively rich.


Gotcha.

That does make sense.

Thanks.


You are welcome. It is nice with these little engines because they have easy to control variables which makes troubleshooting them pretty darn simple most of the time

 

[Vikas]

To answer Trav's question, the throttle was wide open and the choke was off. The engine was cold (may be slightly warm but definitely NOT hot, I can remove the plug by hand).

Overkill's assertion that dry is useless is something which I am hearing first time! I am certainly not challenging it but I would like to have more discussion on it.

Dry compression is what engine will see during the running. Wet compression is used to determine if valves or rings is causing the loss in compression.

 

[Vikas]

It should also be noted that I am losing/burning some oil as the level goes down every time I cut the grass. I lose about two cross-hatches on the dipstick for about 2 hour running. There are four cross-hatches between add and full mark.

 

[OVERKILL]

Originally Posted By: Vikas
To answer Trav's question, the throttle was wide open and the choke was off. The engine was cold (may be slightly warm but definitely NOT hot, I can remove the plug by hand).

Overkill's assertion that dry is useless is something which I am hearing first time! I am certainly not challenging it but I would like to have more discussion on it.

Dry compression is what engine will see during the running. Wet compression is used to determine if valves or rings is causing the loss in compression.


To clarify, I define wet and dry as follows:

Dry: The engine has sat overnight, you run a compression test on a cold engine with what is a "dry" cylinder, since the oil will have, for the most part, drained off the walls.

Wet: The engine has been running for a while until warmed up a bit. Compression test is performed at this point. It is assumed the cylinder is "wet" at this point, since the oil has had a chance to be distributed on the bore and piston and things have expanded to represent the operating conditions of the engine.

"Wet" is oft replicated with some lube tossed into a cold (dry) cylinder to get an idea of what I've defined above.

That's how I was taught to do wet and dry tests.

It was made clear that dry was pretty much just to determine if there wan't a serious mechanical defect. If you were trying to contrast compression against a spec, you used the wet method.

If wet showed OK compression, the next step was a leak-down test.

 

[Trav]

Quote:
Wet: The engine has been running for a while until warmed up a bit. Compression test is performed at this point. It is assumed the cylinder is "wet" at this point, since the oil has had a chance to be distributed on the bore and piston and things have expanded to represent the operating conditions of the engine.

"Wet" is oft replicated with some lube tossed into a cold (dry) cylinder to get an idea of what I've defined above.



I was following until this point. Engine oil should never get above the compression ring causing the "wet condition" under normal operating conditions in a good engine.
If it did you would have an oil burner.

While its true that compression will probably be higher in a warm engine good rings can expand enough cold to at least provide good enough compression for the engine to run properly.
A diesel is a good example, worn rings or bore in a diesel will cause hard/no starting because it cant build enough compression.

The way i was taught is warn engine, WOT, no oil should give an accurate reading.
Wet: a little oil oil down the cylinder.
If compression increases its rings or bore issues if it doesn't its valves.

Apologies if i am misunderstanding something.

 

[OVERKILL]

Originally Posted By: Trav
Quote:
Wet: The engine has been running for a while until warmed up a bit. Compression test is performed at this point. It is assumed the cylinder is "wet" at this point, since the oil has had a chance to be distributed on the bore and piston and things have expanded to represent the operating conditions of the engine.

"Wet" is oft replicated with some lube tossed into a cold (dry) cylinder to get an idea of what I've defined above.



I was following until this point. Engine oil should never get above the compression ring causing the "wet condition" under normal operating conditions in a good engine.
If it did you would have an oil burner.

While its true that compression will probably be higher in a warm engine good rings can expand enough cold to at least provide good enough compression for the engine to run properly.
A diesel is a good example, worn rings or bore in a diesel will cause hard/no starting because it cant build enough compression.

The way i was taught is warn engine, WOT, no oil should give an accurate reading.
Wet: a little oil oil down the cylinder.
If compression increases its rings or bore issues if it doesn't its valves.

Apologies if i am misunderstanding something.



I'm saying that the at-temp readings should be the in-line with or the same as the wet readings (oil down the bore). Where dry readings (cold engine) are often significantly lower and of much less value when trying to compare against a spec, which is IIRC, given wet or @ temp.

When the engine has run, you have a "wet" bore (think ring pack area, not oil in the actual cylinder above the crown of the piston). I'm not saying you have an oil burning setup, but a wet bore defined as one that has had lubricant applied to it (which a bore of an engine that has just run does) which aides in ring seal, regardless of how good a job the oil control rings are doing. If they stopped all lubrication, the engine would of course seize. I think we can agree on that

So the warm reading is the one he should be using to compare against the spec given by the manufacturer. If he cannot get a warm reading, then wet should give a comparable reading. Dry will always be low. If the reading is within spec (and in this case, it is) then a leak-down test would be next on my list

I don't recall ever coming across a manual for any of the gear I've worked on listing a dry compression spec. It was always wet or warm. And I was taught that dry was pretty useless for anything other than "yep it has compression" or "no it has really bad compression", neither of which required a gauge

 

[Trav]

I guess the problem i am having is with the word "dry".
I never thought of cold bores being dry but of course you wouldn't do a compression test on a cold engine and expect meaningful results other than it does have adequate compression to start which is a common test on no start diesels.

Vikas did say he performed a warm test and while not up to full operating temp which should have gotten plenty of oil on the bore and IMO a decent reading.
I'm going to have to reread this whole thread again, something is not fitting together for me.

It has always been my understanding that oil down the plug hole will create a temporary seal in a cylinder with worn rings or a worn bore.
This is honestly the first time in 40 yrs i have heard differently.

Check out page 46&47 this is what i was taught when i first started, course this is more modern

http://people.cpcc.edu/~fse2680e/AUT%20116A%20%20General%20Engine%20Diagnosis%20(Student%20Workbook).pdf

 

[demarpaint]

Wet vs. dry compression testing can be confusing I think. The way I was taught was to have the engine at operating temps then check compression. Wet compression referred to squirting oil into the cylinder/cylinders that were low and see if it comes up. This is also done on a warmed up engine.

Then as Trav stated: Wet: a little oil oil down the cylinder.
If compression increases its rings or bore issues if it doesn't its valves.