The Case of the Bouncing Quitting Go Kart: Carburetor Grief

You may have run into this or you may run into this where you are riding your go kart on a bumpy, gravely driveway and suddenly the go kart stops running properly. It just up and quits.

“Why would the go kart suddenly quit?” Is the question in your mind and “What would cause the go kart engine to stop running, since obviously nothing touched it?”

What you will run into is that when you are riding a go kart on a rough surface the engine will be bounced up and down and in this ” bouncing up and down” the carburetor is jostled up and down. The carburetor inside has a bowl, and inside the bowl is a float that floats literally on gasoline. When the go kart is bounced up and down the float can be bounced up or down and typically will jammed in the needle valve in its seat. It literally jams the needle valve into its seat and the only way to get it released is to jostle it again.

The jostling effect usually comes when you start up the engine in choke it because that’s all that will that will cause the engine to run. It will run almost indefinitely and that’s a symptom that you jammed needle valve. Typically we will frantically start adjusting needle jets trying to get things to work better, just so we can limp home. We will discover however that it is probably the float inside the carburetor causing all the grief.

If this continues to be a problem you have an alternative plan, and that is to buy a new diaphragm carburetor, or find a new carburetor that has no float in it. You see the float is designed to regulate the gas requirements for the engine. A “floated” carburetor is designed to run on a level surface not a surface that is a hill or surface that is constantly being bumped. The diaphragm carburetor however is used on things that are bounced around a lot and change angle positions a lot. For instance they are found in weed wackers and chainsaws. The best way to find a diaphragm carburetor is to go to a local small engine repair store and purchase yourself a diaphragm carburetor that will meet the CFM requirements for your engine. Also you can shop on eBay and find some second-hand used diaphragm carburetors. You need to make sure that you get the right size carburetor otherwise you will be starving your engine for its gas requirement.

And finally the engines that are most susceptible to this particular ailment are engines I have bowl-float combinations. Some of the manufacturers have come up with rubber tipped needle valves which help solve this problem, however you will discover that even going up hills can be an issue so in case you’re wondering why your go kart is quitting after you’ve been running it over bumps and or going up hills, it is because of this float needle jamming issue.

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  1. I bought a gokart at a garage sale. It ran fine the first day but started to die. I don.t have a float valve carb setup so that cant be the problem. I changed the spark plug and it did not help. The compression seems fine when I start it. It will start relatively easy and idle but when its time to go it stalls. The spark plug i changed had alot of carbon black powder on it Just FYI. Any suggestions?

    • Mike, after looking at your previous comment about a black wire, I am guessing that might be part of it. See the following article on ignition systems for more info: Click Here; Otherwise if the ignition is sound, then the real problem is more than likely in the following areas:

      – Fuel Administration: Carb
      – Combustion Chamber Sealing

      What typically will happen on a poor sealing combustion chamber is that the engine will start and run but will quit after the engine is warmed up. Typically this is cause by a poor seating valve which is leaking back into the carb causing vapor lock. Additionally you could have a worn out exhaust valve that leaks more as the engine heats up causing the engine to have less power as it heats up, eventually just quitting.

      Always start at the simplest however, and that is to take that carb apart and clean everything with carb cleaner. Every hole and orifice must be free of gunk. Also all the seals (rubber gaskets) must be in good flexible condition, especially those on diaphragm carbs.


  2. OK… before I read the responses I took apart the fuel system on my gokart and cleaned the Carb the best I could. I also flushed out the gas tank the best I could with the knowledge I have. There is a long tube and a short tube coming out of the carb. The long tube goes to the bottom of the tank and the short tube sits in a shallow pan at the top of the tank but there is no float in there. When I was done cleaning it out it ran like a top… better than I could have imagined. Low idle and quick pickup… it was awesome. It seems when the tank is full of gas it runs great. When in goes down about an inch or so it dies and when I fill it again it runs great and so on. There is a problem (I think) with the gas tank and a sponge like thing in there starting to deteriorate leaving a debris all over the bottom of the tank. Is the sponge necessary in the operation of the fuel system. I am certain that it is clogging the long tube coming from the carb. Can I take out that sponge like thing in there and will it be ok to drive without it?

  3. BTW I don’t see a diaphragm on this carb. I have changed diaphragms on lawn mowers before but this one does not have one nor does it have a float valve.

    • Here is a great example of running in circles and trying to evaluate an engine problem. Number one thing about engines is identify the make and model.

      I am guessing from the description that it is a 5 hp Briggs, based on your description of the carb. The carb on a Briggs does have a long tube that goes into the tank, and typically has a screen at the end of the sucker tube.

      The second area, with the short tube, is short because that is the resevoir pool, or reserve area (equivalent to the bowl/float on the standard carb) this too has a screen at the end of the sucker tube.

      The diaphragm is on the left side, or the side closest to the exhaust port. It works as a pump pulling the gas up into the resevoir pool. The actual carb action takes place in the secondary pool area and is connected to a jet metering port on the right side or the side of the recoil.

      Again if this carb has been totally dismantled it should function properly. You are probably right that the foam material is getting sucked in and clogging the carb up.

      The best thing you can do is go to a small engine shop and get the replacement tube, or a screen filter attachment for the end of the tube.

      Additionally, the tank needs to be cleaned thoroughly. This can be accomplished by putting ball bearings in the tank and then shaking the tank around to rattle an rust loose. Be sure to make sure it doesnt rust anymore.


  4. Last thing… can I take the sponge out of the carb so it does not deteriorate any more causing the same problem? Will it run properly without the sponge.

  5. There is a seal between the tank and carb that must be sealed! If the tank is rusty or the seal is bad the carb will suck air instead of gas. That may show at idle and may not, it depends on how bad the leak is. It will starve the carb of fuel causing the engine to die… I was able to put pressure on the tank and and rev it up to confirm. My tank was rotting so I had to replace it. I went ahead and replaced the diaphram while I had better access (tank off). Ran like top…

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