IH 300 Utility Carburator

pwyld

Member
I believe the needle valve on the carburetor is not the correct one. If I close it completely the engine keeps running. My
question is how do you determine if you have the right needle valve, or if the needle or orifice in the carburetor is worn? I
can make a new needle valve, or ream the orifice if I know the correct dimensions. The carburetor is 361525R2. Any
suggestions.

Thanks
a158099.jpg

a158100.jpg

a158101.jpg

a158102.jpg
 

That is not the needle valve. That is your low speed idle/air adjustment screw. If adjusting that screw either in or out makes no difference in how the engine runs, it is time to remove the carb and give it a thorough cleaning. It is not a job for someone with little experience.
 
As rusty say that is the idle jet and screwing in all the way in makes it richer but also pretty much only at an idle. At higher RPM it is running off the man jet and the idle jet will do little or nothing
 
It is idle mixture screw alright. BUT, on that tractor, it is not an air bleed like the older IH carburetors. It is a mixture screw so it is air and gasoline and screwing it out makes it richer. It is in the books. At any rate, it is to adjust for best idle and that is at low rpm's, like below maybe 600 - 800 rpm or so as from there on up the carburetor starts to operate on the high speed, nozzle, air bleed main jet etc.
 
(quoted from post at 14:37:26 04/23/17) It is idle mixture screw alright. BUT, on that tractor, it is not an air bleed like the older IH carburetors. It is a mixture screw so it is air and gasoline and screwing it out makes it richer. It is in the books. At any rate, it is to adjust for best idle and that is at low rpm's, like below maybe 600 - 800 rpm or so as from there on up the carburetor starts to operate on the high speed, nozzle, air bleed main jet etc.

Okay...thanks to everyone. Maybe I got my terminology mixed up. So it is the "idle mixture screw". But Pete, if it is mixing air and gasoline I would of thought it would starve the engine of fuel if completely closed..at idle of course. Rusty..the same if I unscrew it out...at idle. Not sure I understand that.

But what I'm understanding from the forum is that when it is completely closed or opened, the engine never starves for fuel...which I thought it would at some point. I would of thought that if you increased the air:fuel ratio too high the engine would stall out for lack of sufficient fuel mixed with too much air.
 
(quoted from post at 16:11:25 04/23/17)
(quoted from post at 14:37:26 04/23/17) It is idle mixture screw alright. BUT, on that tractor, it is not an air bleed like the older IH carburetors. It is a mixture screw so it is air and gasoline and screwing it out makes it richer. It is in the books. At any rate, it is to adjust for best idle and that is at low rpm's, like below maybe 600 - 800 rpm or so as from there on up the carburetor starts to operate on the high speed, nozzle, air bleed main jet etc.

Okay...thanks to everyone. Maybe I got my terminology mixed up. So it is the "idle mixture screw". But Pete, if it is mixing air and gasoline I would of thought it would starve the engine of fuel if completely closed..at idle of course. Rusty..the same if I unscrew it out...at idle. Not sure I understand that.

But what I'm understanding from the forum is that when it is completely closed or opened, the engine never starves for fuel...which I thought it would at some point. I would of thought that if you increased the air:fuel ratio too high the engine would stall out for lack of sufficient fuel mixed with too much air.

Turning that screw in too far, or OUT too far, SHOULD cause the engine to run very poorly, and yes, maybe even KILL the engine. If turning that screw in or out has very little effect, or NO effect at all, that is a good indication that the carburetor is dirty inside. some of the tiny passages are totally plugged up. Only way to cure it is a complete disassambley and thorough cleaning of the carburetor.
 
(quoted from post at 08:42:49 04/24/17)
(quoted from post at 16:11:25 04/23/17)
(quoted from post at 14:37:26 04/23/17) It is idle mixture screw alright. BUT, on that tractor, it is not an air bleed like the older IH carburetors. It is a mixture screw so it is air and gasoline and screwing it out makes it richer. It is in the books. At any rate, it is to adjust for best idle and that is at low rpm's, like below maybe 600 - 800 rpm or so as from there on up the carburetor starts to operate on the high speed, nozzle, air bleed main jet etc.

Okay...thanks to everyone. Maybe I got my terminology mixed up. So it is the "idle mixture screw". But Pete, if it is mixing air and gasoline I would of thought it would starve the engine of fuel if completely closed..at idle of course. Rusty..the same if I unscrew it out...at idle. Not sure I understand that.

But what I'm understanding from the forum is that when it is completely closed or opened, the engine never starves for fuel...which I thought it would at some point. I would of thought that if you increased the air:fuel ratio too high the engine would stall out for lack of sufficient fuel mixed with too much air.

Turning that screw in too far, or OUT too far, SHOULD cause the engine to run very poorly, and yes, maybe even KILL the engine. If turning that screw in or out has very little effect, or NO effect at all, that is a good indication that the carburetor is dirty inside. some of the tiny passages are totally plugged up. Only way to cure it is a complete disassambley and thorough cleaning of the carburetor.

Thanks. Yes...I do notice a difference when I adjust the idle mixture screw.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top