bertsmobile1
Lawn Royalty
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- Nov 29, 2014
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The only time I replace a mower carb is when the hole for the throttle butterfly pivot has flogged out so oval that the butterfly an not operate normally.
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Engine Starts Easy, & Runs, but dies after 1 to 10 minutes, or Under Load.
- Thread starter Timothy White
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Export threadTimothy White
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I have to leave soon so no time to give extended replies to the various posts, however an update and a question:
So I found a local shop that sold me a sort of "rebuild kit" (more parts than some, less than others), and I replaced the needle valve and seat and the EXACT SAME THING ONLY WORSE. This time the bowl was at even higher of an angle, and when I disassemble the carburetor AGAIN, the bowl was almost dry. Like maybe a teaspoon at the bottom of the bowl. But also fine grey powder, like a deteriorating fuel line. Didn't think to replace that, and now I'm certain I have to.
So the new valve looks exactly the same as the old, and the new seat is someone lower, but harder than the old one. The old seat is a red-orange rubber and the new one is more yellow-green and feels like it has more plastic, less rubber than the old one.
I've looked at this thing for HOURS today and I'm convinced that for some reason the needle value is forcing the bowl too high. The guy at the parts shop told me "grooved side towards the carburetor, smooth side towards the needle valve", but I've flipped it both ways and it still rides high. So here's my theory:
MY THEORY:
I wonder if someone didn't try to convert an autochoke engine without a primer bulb by changing-out the carburetor to one that has the holes/pathways for priming it. I could post pics of the carb. I'm wondering if this carburetor is not the one that came with the mower at the factory, and that's why the needle valves (both old and new) are too long.
Either that or for some reason I can't push the new seat down the bore deep enough, and so the seat is riding high, which makes the needle value ride high, which drives the bowl down and it closes off prematurely.
Or what, IDK.
Ideas?
I can post pics.
So I found a local shop that sold me a sort of "rebuild kit" (more parts than some, less than others), and I replaced the needle valve and seat and the EXACT SAME THING ONLY WORSE. This time the bowl was at even higher of an angle, and when I disassemble the carburetor AGAIN, the bowl was almost dry. Like maybe a teaspoon at the bottom of the bowl. But also fine grey powder, like a deteriorating fuel line. Didn't think to replace that, and now I'm certain I have to.
So the new valve looks exactly the same as the old, and the new seat is someone lower, but harder than the old one. The old seat is a red-orange rubber and the new one is more yellow-green and feels like it has more plastic, less rubber than the old one.
I've looked at this thing for HOURS today and I'm convinced that for some reason the needle value is forcing the bowl too high. The guy at the parts shop told me "grooved side towards the carburetor, smooth side towards the needle valve", but I've flipped it both ways and it still rides high. So here's my theory:
MY THEORY:
I wonder if someone didn't try to convert an autochoke engine without a primer bulb by changing-out the carburetor to one that has the holes/pathways for priming it. I could post pics of the carb. I'm wondering if this carburetor is not the one that came with the mower at the factory, and that's why the needle valves (both old and new) are too long.
Either that or for some reason I can't push the new seat down the bore deep enough, and so the seat is riding high, which makes the needle value ride high, which drives the bowl down and it closes off prematurely.
Or what, IDK.
Ideas?
I can post pics.
bertsmobile1
Lawn Royalty
- Joined
- Nov 29, 2014
- Threads
- 65
- Messages
- 24,995
Pictures are always good.
And yes, never any reason to assume what is on an old engine is what it left the factory with.
Regardless, the float on just about all carbs should sit flat when turned upside down.
I like to fit the carb without the bowl and check the fuel flow by moving the float by hand.
The bowl itself could be wrong.
A lot of cheap copy carburettors have shorter float bowls ( one way to make them cheaper )
Thus they have smaller floats & shorter needles.
So when an original rebuild kit is fitted into the copy carb, it runs very lean if at all.
The converse is also true with the rebuild kits for the cheap copy carbs going into an original carb.
In my case it was with Tecumseh H 30 carbs, but since being aware of this I have noticed the same thing with Loncin carbs & the Honda carbs they are copied from.
You can fit a Loncin to a Honda & fit a Honda to a Loncin as complete carbs but the rebuild kits might not transpose.
And yes, never any reason to assume what is on an old engine is what it left the factory with.
Regardless, the float on just about all carbs should sit flat when turned upside down.
I like to fit the carb without the bowl and check the fuel flow by moving the float by hand.
The bowl itself could be wrong.
A lot of cheap copy carburettors have shorter float bowls ( one way to make them cheaper )
Thus they have smaller floats & shorter needles.
So when an original rebuild kit is fitted into the copy carb, it runs very lean if at all.
The converse is also true with the rebuild kits for the cheap copy carbs going into an original carb.
In my case it was with Tecumseh H 30 carbs, but since being aware of this I have noticed the same thing with Loncin carbs & the Honda carbs they are copied from.
You can fit a Loncin to a Honda & fit a Honda to a Loncin as complete carbs but the rebuild kits might not transpose.