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lawn boy 8237 rpm adjustment

#1

impalass

impalass

I noticed that the rpm increased on the the engine and i tried to reduce the rpm by the collar and nothing happened. One odd thing is when i remove the air filter element the rpm dropped about 400 rpm. When i move the throttle from high to low nothing happens. The carb has a main jet adjustment for the fuel. this is a f-engine.


#2

robinb66

robinb66

On the F series engines there is no throttle rpm adjustment, there is a small set screw on the side of the body called an atmosphere adjustment screw. According to the manual to adjust turn all the way in then open a half turn start it up and let it run till it's warm, if not running right turn another half turn and wait five minutes. Do this till she runs right or until she runs at the speed you need. Also you say she drops in RPM's when you remove the filter. it sounds like you might need to clean your carb, seeing as how she has higher rpm's with the filter then it sounds like she's starving for gas, just my opinion. Hope this helps!!:thumbsup:


#3

WhyZed

WhyZed

Depends on the model of carburetor if it has altitude adjustment or not.
My F models carb, I have a main jet adjustment and no adjuster for altitude.
On my D409, I have an altitude adjuster and no main jet adjuster.
These adjusters are for fine tuning and not rpm control.

On my F, the RPM adjustment is the wind vain governor. There is a white plastic wheel adjuster on top of the carb, under the flywheel.
On this model, I turn this white wheel counter-clockwise and my RPM increases, clock-wise decreases (or the other way - doesn't matter) 50rpm per click and it works good.

I have my D409 apart right now and can see the governor system it is totally different, I don't see an adjuster but haven't looked to had yet.

There is a round metal flap in the air venturi in the carb. The lever or mechanism that moves that flap is your rpm/speed/throttle.


#4

WhyZed

WhyZed

impalass said:
Last edited by impalass; Today at 01:08 PM.
Click to expand...

When you re-word your entire post and ask a different question then the original posts question was, it's hard for others that might have the same question find the answer they are seeking. :thumbsup:

The reason engines increase in rpm is do to more air (more air in the air to fuel mixture) entering the combustion chamber, period. An engine will run it's fastest just before it seizes.
The main jet should be adjusted a bit richer than serging for highest power. The man jet should be adjusted for optimum performance only after the engine, including the air/fuel/spark/exhaust are optimal. The main jet adjustment is not a bandage adjuster, it is a fine adjustment for a healthy engine.

Temperature is a big tuning 'if'. If the motor was running perfect in hot sticky weather and suddenly it is cold outside, the motor could be now running lean.

There is a chance a spec of dirt has clogged an orifice in the carb. Clean it first.

Take the cowling off and make sure the wind vain is free.


#5

impalass

impalass

WhyZed said:
When you re-word your entire post and ask a different question then the original posts question was, it's hard for others that might have the same question find the answer they are seeking. :thumbsup:

The reason engines increase in rpm is do to more air (more air in the air to fuel mixture) entering the combustion chamber, period. An engine will run it's fastest just before it seizes.
The main jet should be adjusted a bit richer than serging for highest power. The man jet should be adjusted for optimum performance only after the engine, including the air/fuel/spark/exhaust are optimal. The main jet adjustment is not a bandage adjuster, it is a fine adjustment for a healthy engine.

Temperature is a big tuning 'if'. If the motor was running perfect in hot sticky weather and suddenly it is cold outside, the motor could be now running lean.

There is a chance a spec of dirt has clogged an orifice in the carb. Clean it first.

Take the cowling off and make sure the wind vain is free.
Click to expand...

I said when i remove the air filter element the rpm drops not increases. I had the carb apart and it is clean and when i reinstall the carb the vane is free to move.


#6

WhyZed

WhyZed

Ya, I read that..

Is it consistent? Can you put the filter back in and raise the rpm? Can you remove it again & recreate the change?

Knowing this and we will try to help you get your mower fixed up. :thumbsup:


#7

impalass

impalass

WhyZed said:
Ya, I read that..

Is it consistent? Can you put the filter back in and raise the rpm? Can you remove it again & recreate the change?

Knowing this and we will try to help you get your mower fixed up. :thumbsup:
Click to expand...

Yes it is consistent. Even with the filter removed the rpms do not change when i move the throttle lever back and forth.


#8

WhyZed

WhyZed

Morning,

Can you see the butterfly in the carb venturi?
Can you move the lever that the butterfly is attached to and change the rpm?


#9

impalass

impalass

WhyZed said:
Morning,

Can you see the butterfly in the carb venturi?
Can you move the lever that the butterfly is attached to and change the rpm?
Click to expand...

That is the lever i am referring to. One end of the spring is attached to the lever and the other end of the spring is attached to the round collar.


#10

WhyZed

WhyZed

Can you open & close the butterfly and change the rpm?
Did this problem start after you took the carb off?

There is a Dude on youtube named jon3800, I think you are having the same problem he was having. He found the lever that's links the carb to the governor was flipped over and locked fwo (full wide open).

As much detail as possible. The air filter scenario is pretty strange, if the filter is touching (opening) the butterfly when you put it in could be what is raising the rpm when installed.


#11

impalass

impalass

WhyZed said:
Can you open & close the butterfly and change the rpm?
Did this problem start after you took the carb off?

There is a Dude on youtube named jon3800, I think you are having the same problem he was having. He found the lever that's links the carb to the governor was flipped over and locked fwo (full wide open).

As much detail as possible. The air filter scenario is pretty strange, if the filter is touching (opening) the butterfly when you put it in could be what is raising the rpm when installed.
Click to expand...
This problem started when i was cutting the grass and the butterfly is to far back for the filter to touch it. Like what i said before i can move to lever from normal to high and nothing happens.


#12

O

oldboys

impalass said:
I noticed that the rpm increased on the the engine and i tried to reduce the rpm by the collar and nothing happened. One odd thing is when i remove the air filter element the rpm dropped about 400 rpm. When i move the throttle from high to low nothing happens. The carb has a main jet adjustment for the fuel. this is a f-engine.
Click to expand...

I have read all the replies, and they are all valid possibilities. The places I would look, make sure throttle plate is not partially dislodged from the plastic throttle shaft, governor spring intact? Dirt inside carb? Also, is throttle shaft worn and pulling air? Crankshaft seals? Another possibility, pto shaft seal.


#13

impalass

impalass

oldboys said:
I have read all the replies, and they are all valid possibilities. The places I would look, make sure throttle plate is not partially dislodged from the plastic throttle shaft, governor spring intact? Dirt inside carb? Also, is throttle shaft worn and pulling air? Crankshaft seals? Another possibility, pto shaft seal.
Click to expand...

Carb is in very good shape as i had it apart and when the engine is hot it starts very goods so i presume that the seals are in good shape. The engine still has lots of power and the compression is 110 PSI.


#14

WhyZed

WhyZed

Hey impalass, sorry we couldn't get this solved for you so far..

Ok, we can assume the carb is tip-top an the governor is fine.
The problem began while you were mowing, so, the next step in the process is the reed valve. Possible a blade of grass or spec of dirt is holding the valve open.

That is all I can think of.


#15

impalass

impalass

WhyZed said:
Hey impalass, sorry we couldn't get this solved for you so far..

Ok, we can assume the carb is tip-top an the governor is fine.
The problem began while you were mowing, so, the next step in the process is the reed valve. Possible a blade of grass or spec of dirt is holding the valve open.

That is all I can think of.
Click to expand...

I found the problem. The spring for the governor was kinked and i was the person who caused the problem. It happen when i was cutting the grass under the spruce tree and the branch hit the lever for the fuel and shut it off. A couple minutes later the mower stopped and i notice that the fuel lever was in the off position so the branch must have hit the spring and causing a kink.
I fixed the kink and the lawn boy is running good again. I will buy a spare spring.


#16

WhyZed

WhyZed

I'm so happy you found the problem, I was sad & thought you gave up & went to a dealer who charged you hundreds of $.

It is very hard to help with the problem when we are not there to see the problem..


#17

S

spanky63

I have an 8237 and the idle is so low that it des when we try to cut grass. The mower ran good for a while but now is bogging down. I know I need a new blade but that shouldn't affect the mower running with some consistency. My mower smokes a lot too even though I mix one bottle of oil with a gallon of gas.


#18

FuzzyDriver

FuzzyDriver

You should start a new thread rather than necromancing this one. : )


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