16.5 Hp Lawn Tractor runs only on (nearly) full choke
I have an MTD lawn tractor (pretty old) with a B & S Model: 42A707
Type: 123801 engine (Opposed L Head Twin Cylinder).
It was running poorly, so I pulled the carburetor and did a complete rebuild;
I replaced all the part that were included in the rebuild kit except for the Welsh Plug,
which seemed tricky and I didn't see what replacing it would do.
I cleaned out all of the passages with aerosol carb cleaner and everything seemed in great shape.
I reinstalled the carb and fired up the engine.
It started right up and ran great, unless I tried to open the choke.
It seemed to me that it must be either starved for fuel on the carburetor intake,
or was leaking air into the cylinders downstream of the carburetor.
The carburetor rebuild went so well you would have a hard time convincing me (though it wouldn't be impossible)
that there was a clogged fuel passage somewhere in it.
On the other hand, I sprayed starter fluid around the carb, intake manifold connection points, etc while it was running
to see if it caused the engine to sputter, but it had no effect.
I considered that the head gaskets might be leaking air, so I tightened those bolts.
They were "not particularly tight" (pardon my technical language) when I got to them. Some were looser than others.
I tightened them all. I did not use a torque wrench. I didn't know what the proper torque would be.
I let the engine run for about ten minutes and it sounded great the whole time (with the choke on almost full).
It was not, however, under load operating the blades or the wheel drive.
I am pretty much at a loss now for what to do.
I suppose I can re-assemble the tractor and just (try to) use it while leaving the choke mostly on full.
That somehow seems wrong to me.
Anyone have some advice?
I have an MTD lawn tractor (pretty old) with a B & S Model: 42A707
Type: 123801 engine (Opposed L Head Twin Cylinder).
It was running poorly, so I pulled the carburetor and did a complete rebuild;
I replaced all the part that were included in the rebuild kit except for the Welsh Plug,
which seemed tricky and I didn't see what replacing it would do.
I cleaned out all of the passages with aerosol carb cleaner and everything seemed in great shape.
I reinstalled the carb and fired up the engine.
It started right up and ran great, unless I tried to open the choke.
It seemed to me that it must be either starved for fuel on the carburetor intake,
or was leaking air into the cylinders downstream of the carburetor.
The carburetor rebuild went so well you would have a hard time convincing me (though it wouldn't be impossible)
that there was a clogged fuel passage somewhere in it.
On the other hand, I sprayed starter fluid around the carb, intake manifold connection points, etc while it was running
to see if it caused the engine to sputter, but it had no effect.
I considered that the head gaskets might be leaking air, so I tightened those bolts.
They were "not particularly tight" (pardon my technical language) when I got to them. Some were looser than others.
I tightened them all. I did not use a torque wrench. I didn't know what the proper torque would be.
I let the engine run for about ten minutes and it sounded great the whole time (with the choke on almost full).
It was not, however, under load operating the blades or the wheel drive.
I am pretty much at a loss now for what to do.
I suppose I can re-assemble the tractor and just (try to) use it while leaving the choke mostly on full.
That somehow seems wrong to me.
Anyone have some advice?