CV461s 16 HP. New aftermarket carb, won't run correctly?
- Thread starter joea99
- Start date
Post a pic of the fuel solenoid. May have a suggestion. It sounds like the replacement carbs are running too lean. Not enough gas getting through them. Check\replace everything from the carb to the fuel tank and run without cap on the tank. If rthat doesn't help, check the valve lash. If all this fails, you can try boring out the main jet a bit at a time till it gets enough gas.
This is a classic example of why I say it's almost always better to keep the carburetor you have, the original one, has opposed to what so many people do in jumping the gun and buying some aftermarket cheap one or even going and buying an oem one because carburetors typically don't wear out. They usually just get clogged up.
Even with OEM stuff, since the quality is much lower today than many of the older machines were working on, you were off and putting on a poorer quality carburetor then you are taking off.
It sounds like there is either an intake air leak somewhere or it is still running lean. My gas is the car is still running late, both of them you've tried.
Even though it's not as common on these, it sounds a little bit like the secondary or what you can call idle speed circuit is also clogged up.
Many of the original carbs had only one mixture screw on them because the other screw was just an idle stop screw..
This mixture screw had little to no effect on the full throttle running but certainly had an effect on the low idle speed.
However if this is passage is totally clogged up it will affect before running speed typically causing a surge.
I have seen people try to make the main jet whole larger to compensate for this when all they really need to do is clean out that secondary idle circuit.
There is also often a little hole or several little holes drilled into the throat / bore of the carburetor closer to the engine side near the main throttle plate.
This is where that passage is drilled to take air to where the screw moves to adjust how much can go through but if that passage gets clogged up it's basically doing nothing.
I run a wire through the inside part of this and on some carburetors like Hondas a wire through the part underneath the screw too but I always blast the whole out and passage out with carb cleaner spray and strong compressed air.
If that doesn't fix it and you don't find an intake leak by spraying carb cleaner around the intake and all other connections to the engine, then you could buy a mini drill kit and enlarge the main jet just a bit.
You have to be very careful because a little bit ends up being too much if you're not.
You basically want to use the bottom sides of the drills to find the one that does go through the current hole size and then go up just to the next one and then put it back together and try it. You hardly ever have to go over two drill sizes otherwise you'll end up in a situation where it runs rich all the time and has low power.
Even with OEM stuff, since the quality is much lower today than many of the older machines were working on, you were off and putting on a poorer quality carburetor then you are taking off.
It sounds like there is either an intake air leak somewhere or it is still running lean. My gas is the car is still running late, both of them you've tried.
Even though it's not as common on these, it sounds a little bit like the secondary or what you can call idle speed circuit is also clogged up.
Many of the original carbs had only one mixture screw on them because the other screw was just an idle stop screw..
This mixture screw had little to no effect on the full throttle running but certainly had an effect on the low idle speed.
However if this is passage is totally clogged up it will affect before running speed typically causing a surge.
I have seen people try to make the main jet whole larger to compensate for this when all they really need to do is clean out that secondary idle circuit.
There is also often a little hole or several little holes drilled into the throat / bore of the carburetor closer to the engine side near the main throttle plate.
This is where that passage is drilled to take air to where the screw moves to adjust how much can go through but if that passage gets clogged up it's basically doing nothing.
I run a wire through the inside part of this and on some carburetors like Hondas a wire through the part underneath the screw too but I always blast the whole out and passage out with carb cleaner spray and strong compressed air.
If that doesn't fix it and you don't find an intake leak by spraying carb cleaner around the intake and all other connections to the engine, then you could buy a mini drill kit and enlarge the main jet just a bit.
You have to be very careful because a little bit ends up being too much if you're not.
You basically want to use the bottom sides of the drills to find the one that does go through the current hole size and then go up just to the next one and then put it back together and try it. You hardly ever have to go over two drill sizes otherwise you'll end up in a situation where it runs rich all the time and has low power.
grumpyunk
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I may have missed it, but am under the impression that the carburetor is a Nikki. I have one so equipped and the ABF solenoid is unique, to say the least. It holds the main jet inside the part that screws into the bottom of the float bowl.
The jet is almost like a coin with a hole drilled.
The aftermarket likely is the more common probe that blocks the fuel to the main jet.
The hunting can be caused by two things in many cases. Loose linkage that has so much slop the governor is always 'chasing' the throttle position, and never 'gets it right'. Solution may be to add a spring to tension the link between the governor arm and the throttle plate bellcrank. Second thing is the holes in the venturi right behind the throttle plate. They allow a smidge of extra fuel when the throttle opens due to load increase and the governor letting the throttle spring pull it more open. If blocked, a 'lean surge' can be caused as the air moves quickly, but the fuel takes a bit more time to get going to catch up to the increased airflow. Make sure the tiny pinholes are open.
A third cause is difference in linkage between the original and the aftermarket. The bellcrank on the throttle shaft will move more or less than the original depending on the radius (distance it is from the shaft center) of the hole the governor link is plopped into. If the hole is closer to the throttle shaft, the governor will move the throttle plate a bit less than the OEM did. If the hole is further away from the throttle shaft, it will move the throttle plate MORE than the OEM. You may have to measure, and select a different hole in the governor arm to get the same amount of motion of the throttle plate for a given motion of the governor arm. Or,you may not have to do anything and it will work out-of-the-box as-is.
I'd check the governor linkage for slop, check the holes in the sidewall of the venturi, and as a last resort get out the tiny drill bits, and work my way up in size in the main jet until it ran well, given everything else is good.
Finally, the idle mixture is used when the engine is running at all speeds. It is not a huge factor, but if it feeds the venturi holes, opening the idle mixture screw a bit may help enrich the fuel mixture and remove the surge.
I personally would not buy a new Nikki, especially for a couple hundred for a mower that is worth maybe $500-600. I would look for a used Walbro from another Kohler/AYP mower, and just plop that on.
tom
The jet is almost like a coin with a hole drilled.
The aftermarket likely is the more common probe that blocks the fuel to the main jet.
The hunting can be caused by two things in many cases. Loose linkage that has so much slop the governor is always 'chasing' the throttle position, and never 'gets it right'. Solution may be to add a spring to tension the link between the governor arm and the throttle plate bellcrank. Second thing is the holes in the venturi right behind the throttle plate. They allow a smidge of extra fuel when the throttle opens due to load increase and the governor letting the throttle spring pull it more open. If blocked, a 'lean surge' can be caused as the air moves quickly, but the fuel takes a bit more time to get going to catch up to the increased airflow. Make sure the tiny pinholes are open.
A third cause is difference in linkage between the original and the aftermarket. The bellcrank on the throttle shaft will move more or less than the original depending on the radius (distance it is from the shaft center) of the hole the governor link is plopped into. If the hole is closer to the throttle shaft, the governor will move the throttle plate a bit less than the OEM did. If the hole is further away from the throttle shaft, it will move the throttle plate MORE than the OEM. You may have to measure, and select a different hole in the governor arm to get the same amount of motion of the throttle plate for a given motion of the governor arm. Or,you may not have to do anything and it will work out-of-the-box as-is.
I'd check the governor linkage for slop, check the holes in the sidewall of the venturi, and as a last resort get out the tiny drill bits, and work my way up in size in the main jet until it ran well, given everything else is good.
Finally, the idle mixture is used when the engine is running at all speeds. It is not a huge factor, but if it feeds the venturi holes, opening the idle mixture screw a bit may help enrich the fuel mixture and remove the surge.
I personally would not buy a new Nikki, especially for a couple hundred for a mower that is worth maybe $500-600. I would look for a used Walbro from another Kohler/AYP mower, and just plop that on.
tom
That is pretty much what mine looks like, but it has two leads coming out of it.
Measures about 20 ohms, but does not actuate when putting a battery to it. Sadly the battery has seen better days and only puts out 10 VDC.
I'm gonna soak the solenoid, threads down, in some vinegar and salt solution overnight, maybe that will clean up the corrosion.
I wondered about some of those points. Now that snow has covered the ground, I looked over the carbs and am having difficulty determining which jets should be looked at and maybe drilled. The throttle link I will examine.
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No Jets should be drilled at all!
98 times out of 100 if somebody drills the jet or even attempts to enlarge it at all, they will go too large and the carb will now be too rich forever.
Running a soft wire like a couple strands of copper wire twisted together with the end it snipped off cleanly and chamfered is an ideal way or I use some of the very cheap multi-pack assortment of springs that I unwind until I find one just the right thickness to run through the hole a few times.
I'm guessing that carburetor is aftermarket and I have no desire to mess with any of those because many of them are wrong from the get-go.
I've ended up with a few of them and use them for parts to Frankenstein other things back together before but I don't see removable Jets like should be present in the style carburetor.
The brass jet in the side of the aluminum tube going down into the bowl should stick out more and be removable from a slot in it for a flathead screwdriver.
Regardless, this is where you would run a wire through and blow it out with carb cleaner and compressed air to make sure it's clean.
Many of these style carbs that don't have the jet there will have it up inside of this middle tube and that flat brass looking land up in there won't be visible but rather it will have a brass screw in jet with the slot for a flat head screwdriver again so you can unscrew it and remove it and the emulsion tube above it and clean everything out well with carb cleaner and compressed air.
On this one it looks like you can run your wire up through the bottom there but once it's back on you're going to have to determine whether the engine is running rich or lean.
I haven't read back through the entire thread to see if this was mentioned before but it's usually pretty easy to determine by adding a little bit of choke or my preference is to use my finger or thumb or just a folded over shop cloth to slightly block the throat of the carb to see if that makes it stop surging and smooth out and speed up or if it makes it continue to burble and run even worse which means it's rich.
I tell people to never take off the original carburetor or try to replace it because nine times out of 10 you're putting a worse quality carburetor on than the one you're taking off.
Most carburetors do not wear out or fail, they simply get clogged up.