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GX240 carb issues
#1
A
alabama pat
A
alabama pat
I am working on a 8 hp GX240 honda motor for a friend.He claims that the motor kept quitting and he thought the carb needed to be cleaned out.When he attempted to buy a kit to rebuild the carb, they talked him into buying a new carb as it was almost the same price.
He replaced the carb and now according to him the crankcase is always full of both gas and oil.He let this thing sit for almost three years until he asked me to take a look.
I found the crankcase full of both gas and oil as he had stated,and the motor was missing a spark plug,so I am aware that someone has been here before me.I also attempted to get a rebuild kit to no avail,and I also bought a new carb and a new plug.I put the new carb on and replaced the plug and attempted to start the motor.After much pulling or the recoil rope I reviewed a few things.The carb was getting gas and the fuel line was clear.There was spark to the plug.
I sprayed a quick burst of starting fluid in the intake and the motor fired right up,but only ran for a few seconds,or until the starting fluid ran out.It did that a few times and never did pick up any gas from the carb.
I took a compression check and it is on the low side at approx 70 -80 pounds.
Does anyone have any ideas as to the cause,and if there is something else I can try?
He replaced the carb and now according to him the crankcase is always full of both gas and oil.He let this thing sit for almost three years until he asked me to take a look.
I found the crankcase full of both gas and oil as he had stated,and the motor was missing a spark plug,so I am aware that someone has been here before me.I also attempted to get a rebuild kit to no avail,and I also bought a new carb and a new plug.I put the new carb on and replaced the plug and attempted to start the motor.After much pulling or the recoil rope I reviewed a few things.The carb was getting gas and the fuel line was clear.There was spark to the plug.
I sprayed a quick burst of starting fluid in the intake and the motor fired right up,but only ran for a few seconds,or until the starting fluid ran out.It did that a few times and never did pick up any gas from the carb.
I took a compression check and it is on the low side at approx 70 -80 pounds.
Does anyone have any ideas as to the cause,and if there is something else I can try?
#2
I
ILENGINE
I
ILENGINE
Compression is suppose to be 85-121 according to the honda engine shop manual. So that could be part of the problem. the other thing to check would be the low oil sensor. Try unplugging it temporarily to see what happens.
#3
A
alabama pat
ILENGINE,
I removed the low oil sensor wire and there was no difference.I rechecked the compression today in the hope that I had made a mistake in the poor light conditions of last evening.The compression did not improve with the sunlight,and in fact it appeared to be lower today.The compression that I took several times today was right around 70 pounds.I took it before and after I had run it using the starting fluid.It made no difference,both time around 70 pounds.
Could the low compression cause the motor to fail to pick up the fuel into the carb?
A
alabama pat
Compression is suppose to be 85-121 according to the honda engine shop manual. So that could be part of the problem. the other thing to check would be the low oil sensor. Try unplugging it temporarily to see what happens.
ILENGINE,
I removed the low oil sensor wire and there was no difference.I rechecked the compression today in the hope that I had made a mistake in the poor light conditions of last evening.The compression did not improve with the sunlight,and in fact it appeared to be lower today.The compression that I took several times today was right around 70 pounds.I took it before and after I had run it using the starting fluid.It made no difference,both time around 70 pounds.
Could the low compression cause the motor to fail to pick up the fuel into the carb?
#4
B
bertsmobile1
Yes.
However the starter fluid can also strip oil off the bore walls.
Usually your symptoms are those of a blocked carb main jet.
Squirt a little oil down the plug hole and turn the engine over slowly a few time to distribute the oil.
If the compression is 10% or more higher then it needs rings at a minimum.
I never get fussed about compression numbers as there are a lot of things that can affect the actual number.'
What is important is the difference between the wet & dry readings using the same procedure.
B
bertsmobile1
ILENGINE,
I removed the low oil sensor wire and there was no difference.I rechecked the compression today in the hope that I had made a mistake in the poor light conditions of last evening.The compression did not improve with the sunlight,and in fact it appeared to be lower today.The compression that I took several times today was right around 70 pounds.I took it before and after I had run it using the starting fluid.It made no difference,both time around 70 pounds.
Could the low compression cause the motor to fail to pick up the fuel into the carb?
Yes.
However the starter fluid can also strip oil off the bore walls.
Usually your symptoms are those of a blocked carb main jet.
Squirt a little oil down the plug hole and turn the engine over slowly a few time to distribute the oil.
If the compression is 10% or more higher then it needs rings at a minimum.
I never get fussed about compression numbers as there are a lot of things that can affect the actual number.'
What is important is the difference between the wet & dry readings using the same procedure.
#5
A
alabama pat
I did as you suggested and sprayed some oil in the cylinder as I slowly pulled the recoil.There was no difference in the compression numbers,with the oil or without.A steady 70-75 pounds.That should have some indication that the rings are not entirely the main issue.Correct?Could a burnt valve cause the poor compression?I did remove the valve cover and there does not seem to be any issue there.Both valve appear to be working correctly,and the inside of the head and valve cover were very clean and did not appear to be discolored as they were burned.Where to now?
A
alabama pat
Yes.
However the starter fluid can also strip oil off the bore walls.
Usually your symptoms are those of a blocked carb main jet.
Squirt a little oil down the plug hole and turn the engine over slowly a few time to distribute the oil.
If the compression is 10% or more higher then it needs rings at a minimum.
I never get fussed about compression numbers as there are a lot of things that can affect the actual number.'
What is important is the difference between the wet & dry readings using the same procedure.
I did as you suggested and sprayed some oil in the cylinder as I slowly pulled the recoil.There was no difference in the compression numbers,with the oil or without.A steady 70-75 pounds.That should have some indication that the rings are not entirely the main issue.Correct?Could a burnt valve cause the poor compression?I did remove the valve cover and there does not seem to be any issue there.Both valve appear to be working correctly,and the inside of the head and valve cover were very clean and did not appear to be discolored as they were burned.Where to now?
#6
B
bertsmobile1
To get real compression figures for these engines you need to open up the valve last till the mower jerks hard against the pull cord at tdc.
This overirdees the auto decompression.
Then you need to open the throttle fully and pull the cord till the compression meter stops going up.
This is as close to a true compression reading as you can get with a modern small engine.
Generally 70 would be considered marginal.
Now going back to the OP are you sure that the choke is closing off properly when you were trying to start the engine ?
I see there has been 2 carb changes so there aare 2 chances for incorrect linkage adjustments
B
bertsmobile1
I did as you suggested and sprayed some oil in the cylinder as I slowly pulled the recoil.There was no difference in the compression numbers,with the oil or without.A steady 70-75 pounds.That should have some indication that the rings are not entirely the main issue.Correct?Could a burnt valve cause the poor compression?I did remove the valve cover and there does not seem to be any issue there.Both valve appear to be working correctly,and the inside of the head and valve cover were very clean and did not appear to be discolored as they were burned.Where to now?
To get real compression figures for these engines you need to open up the valve last till the mower jerks hard against the pull cord at tdc.
This overirdees the auto decompression.
Then you need to open the throttle fully and pull the cord till the compression meter stops going up.
This is as close to a true compression reading as you can get with a modern small engine.
Generally 70 would be considered marginal.
Now going back to the OP are you sure that the choke is closing off properly when you were trying to start the engine ?
I see there has been 2 carb changes so there aare 2 chances for incorrect linkage adjustments
#7
A
alabama pat
Bertsmobile,
I am not sure just what valve you are refering to when you state that I have to open the valve last.
I have on several attempts spun the motor over five to six times and all attempts have resulted in the same compression readings.It is very difficult to find TDC as the motor has very little compression.Pulling the recoil slowly,or quickly makes no difference.
As far as the choke goes,the butterfly valve closes completely but even when completely shut there is a small gap on the right hand side of the carb body where the the butterfly is squared off about 1/8 of an inch. it can never seal completely.There is no choke linkage as the choke is operated by a lever on the carb body.It is either open or closed.
A
alabama pat
To get real compression figures for these engines you need to open up the valve last till the mower jerks hard against the pull cord at tdc.
This overirdees the auto decompression.
Then you need to open the throttle fully and pull the cord till the compression meter stops going up.
This is as close to a true compression reading as you can get with a modern small engine.
Generally 70 would be considered marginal.
Now going back to the OP are you sure that the choke is closing off properly when you were trying to start the engine ?
I see there has been 2 carb changes so there aare 2 chances for incorrect linkage adjustments
Bertsmobile,
I am not sure just what valve you are refering to when you state that I have to open the valve last.
I have on several attempts spun the motor over five to six times and all attempts have resulted in the same compression readings.It is very difficult to find TDC as the motor has very little compression.Pulling the recoil slowly,or quickly makes no difference.
As far as the choke goes,the butterfly valve closes completely but even when completely shut there is a small gap on the right hand side of the carb body where the the butterfly is squared off about 1/8 of an inch. it can never seal completely.There is no choke linkage as the choke is operated by a lever on the carb body.It is either open or closed.
#8
S
shiftsuper175607
S
shiftsuper175607
The fuel shut off valve is closed?
Does fuel come out the plug on the bowl when you remove the plug?
I put an after market carb on mine and it has a fuel shut off valve.
Does fuel come out the plug on the bowl when you remove the plug?
I put an after market carb on mine and it has a fuel shut off valve.
#9
A
alabama pat
Yes,the fuel shutoff is open.When the plug is removed there is a good flow of gas that comes out of the bowl.
A
alabama pat
The fuel shut off valve is closed?
Does fuel come out the plug on the bowl when you remove the plug?
Yes,the fuel shutoff is open.When the plug is removed there is a good flow of gas that comes out of the bowl.
#10
A
alabama pat
A
alabama pat
Upon doing some research on a few websites looking for parts ,I found a few mentions of an automatic decompression release that is on this model.There appears to be a spring that fails at times,or the cam lever perhaps seizes at times.I am unsure if either one of those failures could cause the issues that I am having,but I am sure neither failure can be good.The motor did run fairly good at low speed using the starting fluid,but that does not mean too much as pretty mush everything will run on starting fluid,just not for long.This motor only ran until the starting fluid ran through it.Anybody have any ideas regarding the decompression possibility?
#11
B
bertsmobile1
They fail the other way.
The decompressor is very somilar to a mechanical govenor in principles and the spring works agains a bob weight to activate the valve lifter at low revs.
Time to pretend you are the queen of spades and "Off with its Head" "off with it's Head"
B
bertsmobile1
Upon doing some research on a few websites looking for parts ,I found a few mentions of an automatic decompression release that is on this model.There appears to be a spring that fails at times,or the cam lever perhaps seizes at times.I am unsure if either one of those failures could cause the issues that I am having,but I am sure neither failure can be good.The motor did run fairly good at low speed using the starting fluid,but that does not mean too much as pretty mush everything will run on starting fluid,just not for long.This motor only ran until the starting fluid ran through it.Anybody have any ideas regarding the decompression possibility?
They fail the other way.
The decompressor is very somilar to a mechanical govenor in principles and the spring works agains a bob weight to activate the valve lifter at low revs.
Time to pretend you are the queen of spades and "Off with its Head" "off with it's Head"