Hello y'all. I have a 17hp Briggs I/C on a Murry LT that will NOT run right. I've soaked the carb for two days in a brand new bucket of carb cleaner, put in a new kit including the needle valve seat, and today replaced the high speed jet with a new one. No matter what I do, it runs rich and yes the choke is full off. It will ALMOST runs smooth but is just short of and spews out small clouds of black smoke. Another thing is the air mixture screw will not kill it if screwed in completely. This has driven me nuts!!!! What in the H___ am I missing??? Someone suggested pulling the choke on to maybe 45 degrees. My reply was it's already running rich so why would I add choke to an already overly rich condition!!! Oh, and I've replaced the plugs too and the spark is great. ANYONE with ANY idea as to why will be GREATLY APPRECIATED!!!!!!!!!
Briggs carb runs rich!
Poot
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Hello y'all. I have a 17hp Briggs I/C on a Murry LT that will NOT run right. I've soaked the carb for two days in a brand new bucket of carb cleaner, put in a new kit including the needle valve seat, and today replaced the high speed jet with a new one. No matter what I do, it runs rich and yes the choke is full off. It will ALMOST runs smooth but is just short of and spews out small clouds of black smoke. Another thing is the air mixture screw will not kill it if screwed in completely. This has driven me nuts!!!! What in the H___ am I missing??? Someone suggested pulling the choke on to maybe 45 degrees. My reply was it's already running rich so why would I add choke to an already overly rich condition!!! Oh, and I've replaced the plugs too and the spark is great. ANYONE with ANY idea as to why will be GREATLY APPRECIATED!!!!!!!!!
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"put in a new kit including the needle valve seat"
Do you mean for the float? If so,how about the needle?
Was there an "o" ring in the seat that may or may not have been removed?
Is the float punctured/saturated with fuel so that it doesn't have the proper buoyancy?
What are the engine #'s?
That way we can tell exactly which engine/carb it is, instead of guessing.
Do you mean for the float? If so,how about the needle?
Was there an "o" ring in the seat that may or may not have been removed?
Is the float punctured/saturated with fuel so that it doesn't have the proper buoyancy?
What are the engine #'s?
That way we can tell exactly which engine/carb it is, instead of guessing.
LOL! Thanks for the replies and sorry about that fella's. Guess some numbers would've been a little helpful huh. The model is #42A707, type #2653E1.
The seat; Yes I meant the float's needle valve seat and replaced the needle valve too. There was no "O" ring in the seat either before or after. The float; it's good, no fluid inside, and is adjusted using as most everyone recommends a #4 bit at the opposite side from the hinge pin. The air filter is new/clean. As for the make of carb, assume it's a Nikki. I say this because on a Walboro I always see their name somewhere on one but this has no name anywhere but as I said, that's an assumption on my part and I could very well be wrong. I bought this mower and the seller said it hadn't been sitting up long. I knew it had because smelling the gas told me it had sat a LONG time. It ran but only if the choke just off of full on. After the rebuild it runs and runs close to right (u can tell it's almost there) with the choke full off but sputters a lot and when it does it lightly black smokes. Every once in a while it'll smooth out for a few seconds then start lightly sputtering again. It's so close to running right it ain't funny....but doesn't.
I forgot to mention this. After letting it sit for a while I can look through the carb and into the intake (straight below the carb) and there's a small puddle of gas standing. First thought was after turning it off MAYBE gas was seeping past the new needle valve seat. Then I remembered it was doing this before I rebuilt the carb, did it after the rebuild, and after taking it off/apart AGAIN and installing a new seat for the float's needle valve, it's still doing this. ARG!!!!!!!!!!!! :hammerhead:
The seat; Yes I meant the float's needle valve seat and replaced the needle valve too. There was no "O" ring in the seat either before or after. The float; it's good, no fluid inside, and is adjusted using as most everyone recommends a #4 bit at the opposite side from the hinge pin. The air filter is new/clean. As for the make of carb, assume it's a Nikki. I say this because on a Walboro I always see their name somewhere on one but this has no name anywhere but as I said, that's an assumption on my part and I could very well be wrong. I bought this mower and the seller said it hadn't been sitting up long. I knew it had because smelling the gas told me it had sat a LONG time. It ran but only if the choke just off of full on. After the rebuild it runs and runs close to right (u can tell it's almost there) with the choke full off but sputters a lot and when it does it lightly black smokes. Every once in a while it'll smooth out for a few seconds then start lightly sputtering again. It's so close to running right it ain't funny....but doesn't.
I forgot to mention this. After letting it sit for a while I can look through the carb and into the intake (straight below the carb) and there's a small puddle of gas standing. First thought was after turning it off MAYBE gas was seeping past the new needle valve seat. Then I remembered it was doing this before I rebuilt the carb, did it after the rebuild, and after taking it off/apart AGAIN and installing a new seat for the float's needle valve, it's still doing this. ARG!!!!!!!!!!!! :hammerhead:
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Did you replace the fuel pump kit at the same time? Could be a pinhole in the diaphragm allowing excess gas to be sucked in?
Is this a 3 or 4 screw fuel pump?
It might be as simple as water in the gas? Did you drain the tank completely? If you think it might be water, put a few oz. of Gas Dri in the tank.
Alcohol absorbs water. Bad thing about it, it absorbs water from the atmosphere/condensation when just sitting.
Is this a 3 or 4 screw fuel pump?
It might be as simple as water in the gas? Did you drain the tank completely? If you think it might be water, put a few oz. of Gas Dri in the tank.
Alcohol absorbs water. Bad thing about it, it absorbs water from the atmosphere/condensation when just sitting.
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Never used a drill bit to set a float before, With the upper body inverted the float should be parallel to the gasket surface, I adjust about 1/16" higher on the side away from the pin.
Check the pilot jet (the screw on the lower front of the base). There is supposed to be a small hole in the tip of this pilot jet, Use a bristle out of a hand wire brush to make sure it's open.
Also, I see you're in Tennessee. Maybe a higher altitude ?
You could try the high altitude jet part# 693499 with the smaller port and see if that solves the problem.
Check the pilot jet (the screw on the lower front of the base). There is supposed to be a small hole in the tip of this pilot jet, Use a bristle out of a hand wire brush to make sure it's open.
Also, I see you're in Tennessee. Maybe a higher altitude ?
You could try the high altitude jet part# 693499 with the smaller port and see if that solves the problem.
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What kind of exhaust[muffler]is on it? Sometimes the wrong back pressure will cause rich/lean conditions....?
When I said the filter was new/clean, I meant it is BRAND new and clean. Not one that's recently new and has been used a little. Some owners who say new can say "It was new....two months ago" but don't consider they could've used it in very dusty conditions so while "new" in their eyes, it could be dirty/clogged. So, it's new AND clean having never been used other then running it in my garage. Ooooook, the float is about 1/16 off level to the high side, inverted. When u said to check the pilot jet on the front lower base. Do you mean the air/fuel mixture screw? I've ran a thin wire through ALL the openings as far as a wire would go and yes I've done so in that opening as well. Just wanted to see if you and I were talking the same lingo here. As for the muffler, I can't SAY that it's stopped up but putting my hand in front of it it does have a LOT of exhaust pressure. I did this to another mower to compare and the pressure feels fairly equal to me. As for altitude, I live in Southwest Tennessee and it's flat here but a high altitude jet IS a thought. I just bought/installed a new jet but it didn't help so maybe your idea would work. It still doesn't ID the cause/reason for this problem which I'd like to know for future use and is a bandaid but heck, if it worked I'm all for it. This mower was bought from a local Walmart (he said) and did not come from a higher altitude area but that doesn't mean it hadn't been changed by someone at some point. However, the jet I just installed was "standard" and not the high altitude jet which was an option. And I'm not trying to poo-poo anyone's helpful idea's or thoughts, it's just that so far I've tried what's been suggested with no change in the problem which is why I've become so frustrated. But y'all please keep trying and I'll keep doing and maybe between all of us we'll hit upon the cause and a fix!!!!!
And yeah, ANY/ALL ideas are GREATLY APPRECIATED!!!!!
And yeah, ANY/ALL ideas are GREATLY APPRECIATED!!!!!
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Well, the elevation at your airport is 243', so I doubt you would be considered "high altitude"! (5000') Unless you live on a mighty steep mountain
DID you do anything to the fuel pump?
DID you do anything to the fuel pump?
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check the seat in the carb i had one that set with water in the gas during the winter froze and cracked the seat used a cheap ear canal scope from the drug store to find also check that the intake valve is seating good hope this helps m,g,
LOL. No, my yard does slope some but far from being considered a mountain!Well, the elevation at your airport is 243', so I doubt you would be considered "high altitude"! (5000') Unless you live on a mighty steep mountain
DID you do anything to the fuel pump?
And I apologize for not answering your question earlier. Yes sir, I rebuilt the fuel pump at the same time as the carb and it is a three screw pump. I am stumped and out of ideas but refuse to drop $142 plus for a new carb...... yet.
I've replaced the float needle vale seat with a new one already. As for the intake..haven't checked the valves. Whether you mean improper stem clearance or the face/seat needing to be resurfaced, how could a valve cause an overly rich condition? Remember, I'm not saying you/your idea are full of it, just asking because I don't know it all and you may teach me something here that I don't know!!!
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because if the valve is not seating un used fuel can @ will blow back into the carb
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Morning John. As for the exhaust idea, probably a good one so I took the muffler off. It didn't change at all and still black smokes just as it did. But hey, don't know til u try, it was worth a shot, and I appreciate the idea/reply.
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That's okay....the reason I asked is that sometimes less backpressure will necesitate a smaller jet. So, in your case, I'm thinking it's running too rich to "remove" [which would make it run richer]but what I really was wondering is if you're using an after market muffler or one that was designed for this application specifically.?
I understand. Nope, it's a stock muffler, the small bulky looking type that kinda resembles a little shoe box for lack of a better comparsion. I've wondered if maybe the ignition is weak. Strong in appearence using a test plug and strong enough to run almost ok but weak enough to not completely run right and fire (burn) the amount of raw gas introduced. Hum.............................
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I'm with Mike, it sounds like one of the valves is either not seating or adjusted too tight. I had a Briggs that acted similar and was also hard as HECK to start. Getting the valves right fixed both.
Also, if this is a twin you may try and start the engine and disconnect one spark plug and then the other. DON'T TOUCH ANYTHING ELSE ON THE MOWER UNLESS YOU ENJOY GETTING SHOCKED!! If it runs the same with either cylinder dead than it is most likely a carb problem. If it runs on one cylinder but not the other, than the one that does not run needs attention. I'm sorry if that's a little hard to follow, but it could help you narrow down your choices.
You gotta love weird little problems on engines that have been sitting. I spent countless hours getting an older briggs running just right after sitting. two months later it tossed a counterbalance through the crankcase. damn:drinkup:
Also, if this is a twin you may try and start the engine and disconnect one spark plug and then the other. DON'T TOUCH ANYTHING ELSE ON THE MOWER UNLESS YOU ENJOY GETTING SHOCKED!! If it runs the same with either cylinder dead than it is most likely a carb problem. If it runs on one cylinder but not the other, than the one that does not run needs attention. I'm sorry if that's a little hard to follow, but it could help you narrow down your choices.
You gotta love weird little problems on engines that have been sitting. I spent countless hours getting an older briggs running just right after sitting. two months later it tossed a counterbalance through the crankcase. damn:drinkup:
A good idea and I follow your train of thought. Ok, it starts right up no problem. I've worked on a lot of cars over 40 years and have seen valves sticking/not fully seated. In some if it were an intake, it allowed some of that cylinders compression to blow by and up/out of the carb which also sometimes carried a little raw gas with it.
Wouldn't this motor too blow compression and probably a little raw gas if an intake wasn't seating? It does neither and I'm not being a smart a__ or meaning to shoot u down, just trying to be objective and think it through before I start tearing it apart.
I did pull the wires and each made a big difference so it's back to the carb?
Hum.....ok, here I'm referring to my motor and not your experience. If a valve isn't seating correctly, how can that cause the piston to pull in MORE gas which apparently is the case since mine black smokes? An unseated valve to any degree diminishes the pistons ability to draw air/fuel and that being noticeable depends on how bad the valve doesn't seat. Whether it's seated correctly or not, whether it has the proper stem clearance or not, an incorrect valve can't cause the piston to pull in more fuel then the carb allows through. An intake with too little clearance WILL affect the running because it can't open enough to allow the required volumn of fuel/air in. If it lacks enough clearance be it either valve, it can't start because the piston can't develop compression or suction. Logical? What do u think??? As for lovin small engnes problems, yeah and I do like a challange but this one has gotten OLD!!! I can't decide whether to continue chasing this problem or run over it with my tractor. Nawwww, if I ran it I'd probably slice/ruin an expensive REAR tire while the fronts remained untouched!!! A sledgehammer would be cheaper. :drinkup:
Thanks!!!
Wouldn't this motor too blow compression and probably a little raw gas if an intake wasn't seating? It does neither and I'm not being a smart a__ or meaning to shoot u down, just trying to be objective and think it through before I start tearing it apart.
I did pull the wires and each made a big difference so it's back to the carb?
Hum.....ok, here I'm referring to my motor and not your experience. If a valve isn't seating correctly, how can that cause the piston to pull in MORE gas which apparently is the case since mine black smokes? An unseated valve to any degree diminishes the pistons ability to draw air/fuel and that being noticeable depends on how bad the valve doesn't seat. Whether it's seated correctly or not, whether it has the proper stem clearance or not, an incorrect valve can't cause the piston to pull in more fuel then the carb allows through. An intake with too little clearance WILL affect the running because it can't open enough to allow the required volumn of fuel/air in. If it lacks enough clearance be it either valve, it can't start because the piston can't develop compression or suction. Logical? What do u think??? As for lovin small engnes problems, yeah and I do like a challange but this one has gotten OLD!!! I can't decide whether to continue chasing this problem or run over it with my tractor. Nawwww, if I ran it I'd probably slice/ruin an expensive REAR tire while the fronts remained untouched!!! A sledgehammer would be cheaper. :drinkup:
Thanks!!!
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"just trying to be objective and think it through before I start tearing it apart."
I don't know that popping the valve covers off and checking the clearance counts as a big tear-down after pulling the carb off and taking it apart, maybe it's just me. :drinkup: And I'm not convinced that a ~20 cu inch cylinder on a briggs would produce as much compression blowout as one on a car.
I would hope pulling either plug wire makes a big difference. Just so we're clear, if it runs the same with the left spark plug unplugged as with the right one unplugged, that indicates that if there is any problem with the cylinder or valves, both cylinders are equally faulty. That's not very likely, so you are back to the carb.
If you're concerned that the spark is weak, pick up a briggs ignition tester. If you get a spark on it, the ignition is fine. Also, IDK about that particular engine, but I think a lot of twins have separate magnetos for each cylinder. So unless they are both weak you should have seen a difference between the two cylinders. Run a search and you'll find a test procedure for the ignition, that's easy enough.
If none of these check out, spend the money on a new carb.
Or drop it off at my place, I'll give you 10 bucks for it.
I don't know that popping the valve covers off and checking the clearance counts as a big tear-down after pulling the carb off and taking it apart, maybe it's just me. :drinkup: And I'm not convinced that a ~20 cu inch cylinder on a briggs would produce as much compression blowout as one on a car.
I would hope pulling either plug wire makes a big difference. Just so we're clear, if it runs the same with the left spark plug unplugged as with the right one unplugged, that indicates that if there is any problem with the cylinder or valves, both cylinders are equally faulty. That's not very likely, so you are back to the carb.
If you're concerned that the spark is weak, pick up a briggs ignition tester. If you get a spark on it, the ignition is fine. Also, IDK about that particular engine, but I think a lot of twins have separate magnetos for each cylinder. So unless they are both weak you should have seen a difference between the two cylinders. Run a search and you'll find a test procedure for the ignition, that's easy enough.
If none of these check out, spend the money on a new carb.
Or drop it off at my place, I'll give you 10 bucks for it.
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