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Discussion Starter · #1 ·
So I've noticed the last few times that I've gone to the dunes that my carburetor is just covered in sand and is stuck there with gas, and I used some brake clean to hose it off and when I spray the accelerator pump the engine craps out. So I'm sure that the accelerator pump is leaking, but do I need a new accelerator pump, or just the seal? And if I do just need a seal does that mean that sand could have gotten in and wore out the accelerator pump, and I should get a new one anyway? Also is there anything I can do to the accelerator pump, or an aftermarket kit that I can get to make it squirt more? Thanks
 

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So I've noticed the last few times that I've gone to the dunes that my carburetor is just covered in sand and is stuck there with gas, and I used some brake clean to hose it off and when I spray the accelerator pump the engine craps out. So I'm sure that the accelerator pump is leaking, but do I need a new accelerator pump, or just the seal? And if I do just need a seal does that mean that sand could have gotten in and wore out the accelerator pump, and I should get a new one anyway? Also is there anything I can do to the accelerator pump, or an aftermarket kit that I can get to make it squirt more? Thanks
I'm going out on a limb here, but my first guess is that you bought the quad used and basically know nothing about it.

If the accelerator pump is leaking, the entire carb need to be checked and serviced by a qualified mechanic.

Simply put, the accelerator pump diaphragm has most likely been damaged by alcohol in the fuel. Simply installing a new pump diaphragm (part number 16021-HM3-L00 @ $72 from Honda) and I do not know anyone who produces a larger volume pump. Why would you want a larger volume pump? If the original pump is functioning and adjusted properly, the off idle bog caused by vacuum drop when the throttle is opened suddenly is adequately over come by the current volume pump. I guess I just don't understand what you hope to accomplish with a large volume accelerator pump?
 

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Discussion Starter · #3 ·
I'm going out on a limb here, but my first guess is that you bought the quad used and basically know nothing about it.

If the accelerator pump is leaking, the entire carb need to be checked and serviced by a qualified mechanic.

Simply put, the accelerator pump diaphragm has most likely been damaged by alcohol in the fuel. Simply installing a new pump diaphragm (part number 16021-HM3-L00 @ $72 from Honda) and I do not know anyone who produces a larger volume pump. Why would you want a larger volume pump? If the original pump is functioning and adjusted properly, the off idle bog caused by vacuum drop when the throttle is opened suddenly is adequately over come by the current volume pump. I guess I just don't understand what you hope to accomplish with a large volume accelerator pump?
Well it doesnt bog off the line it runs great, but I figured if there was an aftermarket one that squirted more fuel, then more fuel equals more power 🤷‍♂️ but I wought it almost 3 years ago from the original owner (that my dad knew) and its 100 percent stock and in immaculate condition. It just started getting sand on the carburetor very recently and by spraying it off I figured out that it idled slower when I sprayed the accelerator pump, which I assumed meant the accelerator pump was leaking fuel and getting gas on the carb, making sand stick to it
 

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Well it doesnt bog off the line it runs great, but I figured if there was an aftermarket one that squirted more fuel, then more fuel equals more power 🤷‍♂️ but I wought it almost 3 years ago from the original owner (that my dad knew) and its 100 percent stock and in immaculate condition. It just started getting sand on the carburetor very recently and by spraying it off I figured out that it idled slower when I sprayed the accelerator pump, which I assumed meant the accelerator pump was leaking fuel and getting gas on the carb, making sand stick to it
Well, you know what assuming does don't you?

There might be a carb problem since it slowed the engine down when spraying off, it may indicate a vacuum leak and this is where you get to start learning fuel systems.

It slowed down because the vacuum leak was momentarily sealed with the cleaner that you sprayed on and the air leaking in was replaced with fuel (any flammable liquid and brake cleaner is highly flammable). So when you shut off the air and replaced it with fuel is slowed down because MORE FUEL IS LESS POWER! More air means more power. The fuel mixed with the air creates a combustible mixture and air (oxygen) supports combustion. The less fuel you can mix with the air the hotter the mixture will burn and the power comes from the heat of the burn. You lean the mixture to increase the heat of the burn, but too lean will burn up the motor, so enough fuel needs to be mixed with the air to cool the burn to the point it burns with adequate heat, but cool enough not to melt the piston. You will discover this when you get into jetting carbs and find out too rich will slow acceleration and limit top speed.

Engine/carb tuning 101 - MORE FUEL IS LESS POWER and MORE AIR IS MORE POWER, but it has to have the correct amount of combustible vapor mixed with the air to burn. OH! and liquid does not burn - only the vapor. They usually teach you this in high school chemistry or high school motor mechanics class.

Have fun.
 

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Start the engine and let it idle... spray a shot of something flammable at various spots where it could leak. If you hear rpm change, that's a spot its leaking. This is a must-do quick test when buying a used snowmobile. Fire it up and give it a shot of ether on the sides of the crank, fast way to find bad crank seals... which are usually always on the mag side /boggle.

-DallanC
 

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Discussion Starter · #7 ·
Start the engine and let it idle... spray a shot of something flammable at various spots where it could leak. If you hear rpm change, that's a spot its leaking. This is a must-do quick test when buying a used snowmobile. Fire it up and give it a shot of ether on the sides of the crank, fast way to find bad crank seals... which are usually always on the mag side /boggle.

-DallanC
Well that's exactly what I did the other day, and spraying the accelerator pump made the idle slow down, and I did it again today and nothing, but it wasn't warmed up, and I'm not sure if I had it warmed up the other day, would that make a difference?
 

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Well that's exactly what I did the other day, and spraying the accelerator pump made the idle slow down, and I did it again today and nothing, but it wasn't warmed up, and I'm not sure if I had it warmed up the other day, would that make a difference?
Depending on where and how much you sprayed, the vapor may have entered the air filter inlet and just inhaling the vapor would change the engine speed.
 

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Discussion Starter · #9 ·
Depending on where and how much you sprayed, the vapor may have entered the air filter inlet and just inhaling the vapor would change the engine speed.
Well then even if I didnt have a vacuum leak, then why is the carb always covered in sand and dust
 

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Well then even if I didnt have a vacuum leak, then why is the carb always covered in sand and dust
I dont understand how a vacuum leak causes buildup on the outside of a carb. Usually fluids leaking from inside out, cause sand/ dust and whatnot to stick.

I find I get sand and dirt build up everywhere ... it sticks to alot of stuff. I dont run in water or muddy conditions (usually, I live in the high elevation desert), but with humidity things are more or less "sticky". Its interesting just how much humidity affects sand. Sand Dunes are distinctly different in size and shape depending on humidity conditions.

But, as long as its not getting inside the engine, and not affecting cooling (caked cooling fins etc) or affecting linkage, I dont care what sticks to the outside of my carb. I spray them down from time to time at home with a hose. I do check inside my intake boots for dust... thats one of the reasons I loathe the KN filters, I've SEEN what gets past them.

But, back to your supposed leaking pump... again spray it with some ether... use a nozzle with a straw to focus the spray to specific points. use very short bursts in specific locations, then wait 10 seconds at least to listen for changes in rpm (and to let the spray dissipate before testing the next spot). You can try it with the throttle in different positions to actuate the pump linkage, its always possible there is a worn spot on the rod somewhere that leaks in one position but not others (unlikely though imo).

Worst case, find a friend with a carb and try swapping for a test.

-DallanC
 

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Discussion Starter · #11 ·
I dont understand how a vacuum leak causes buildup on the outside of a carb. Usually fluids leaking from inside out, cause sand/ dust and whatnot to stick.

I find I get sand and dirt build up everywhere ... it sticks to alot of stuff. I dont run in water or muddy conditions (usually, I live in the high elevation desert), but with humidity things are more or less "sticky". Its interesting just how much humidity affects sand. Sand Dunes are distinctly different in size and shape depending on humidity conditions.

But, as long as its not getting inside the engine, and not affecting cooling (caked cooling fins etc) or affecting linkage, I dont care what sticks to the outside of my carb. I spray them down from time to time at home with a hose. I do check inside my intake boots for dust... thats one of the reasons I loathe the KN filters, I've SEEN what gets past them.

But, back to your supposed leaking pump... again spray it with some ether... use a nozzle with a straw to focus the spray to specific points. use very short bursts in specific locations, then wait 10 seconds at least to listen for changes in rpm (and to let the spray dissipate before testing the next spot). You can try it with the throttle in different positions to actuate the pump linkage, its always possible there is a worn spot on the rod somewhere that leaks in one position but not others (unlikely though imo).

Worst case, find a friend with a carb and try swapping for a test.

-DallanC
Ya, I wouldnt think much of it, but my brothers 400 that is IDENTICAL to mine never has anything stick to it, so that got me wondering, maybe I have a really really small fuel leak??
 
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