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Discussion Starter · #1 ·
Hello I have a ZR120 that suddenly is having a starting problem.

Usually if it sits for a while it will start then die within 20-40 seconds and will not refire until it sits again for a while.

Acts like it runs out of fuel, if I pull the plug plenty of spark but it is dry.

There is plenty of fuel in the tank and it "seems" like the carb bowl has at least some fuel in it after it dies. The filter is not the issue as the line to carb is full of fuel. Vent line is open and I have tried without the cap on the tank. If I disconnect the fuel line from the carb fuel flows well.

Assuming this is a carb issue I have taken the carb apart and cleaned, if I had to guess it would an issue with the float valve, based on my inspection it looks okay but no improvement after cleaning the carb.

Any ideas on this one?
 

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Check the float level and make sure it is set properly. If that is ok then check the flow through the needle and seat with the bowl off the carb. If that all seems ok. Then you may have some dirt in the idle or high speed circuit. I have seen where a small flake of crap will make its way to a jet, needle, or restriction in a circuit and completely plug it. After some time, it settles back down and the engine runs until it gets sucked back up. You said it runs for 20 to 40 seconds which is more likely that it is a fuel delivery problem with getting the fuel into the float bowl. Soak the carb in cleaner over night and blow out all the passages. Make sure the two small holes in the throat of carb body on either side of the butterfly are clear and clean. Those are the idle circuits.
 

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Discussion Starter · #3 ·
Thanks for the notes, I will recheck the carb again with the float bowl off to make sure the flow through the needle is correct and redo the cleaning if necessary.

thanks again
 

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My carb was so crudded, had to take it apart and clean it 3 times so all the sh__ was out...# pulls and she purrssss!!!! :super_happy:
 

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Discussion Starter · #5 ·
Well I had it running fairly well for a while on Saturday, I went back to try on Sunday and the same old issue. Starts and runs for a while then dies, will not refire until I let it set for a while. I am starting to think it is the needle valve on the float? Maybe worn and is sliding in more than it should based on spring pressure when it should actually be open to allow more fuel into the bowl?
 

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Drain the fuel and clean out the tank. Clean the carb again and blow out all the passages in reverse flow with carb cleaner and air. I once saw where a car would run fine and then for no reason run out of fuel and it did it randomly. The carb was clean the fuel pump and filter were new. We pulled the gas tank and found that some one (kids) had put leaves in the fuel tank. The leaves all had circles on them where they would get sucked up to the fuel pickup. I think you have some piece of dirt that blocking a passage and settles back out after some time. Here is a little trick that may help. It will clean the carb and engine (inside). Get a can of Berrymans Chemtool B-12 at an auto parts store or Walmart. Mix it straigh with 2-cycle oil 50:1. With the tank empty, run the kitty on it straight. It won't hurt the engine but it cleans everything, even the carbon on the piston. A college auto shop teacher taught me this one for those people don't want to pay big $$$ for those quadrajet carb rebuilds. This will clean the carb and its passages but will not get rid of a big chuck that may be block a fuel passage. Good luck and let us know what you find.
 

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<div class='quotetop'>QUOTE (Enginerd @ Jan 9 2007, 12:54 PM) <{POST_SNAPBACK}></div>
Drain the fuel and clean out the tank. Clean the carb again and blow out all the passages in reverse flow with carb cleaner and air. I once saw where a car would run fine and then for no reason run out of fuel and it did it randomly. The carb was clean the fuel pump and filter were new. We pulled the gas tank and found that some one (kids) had put leaves in the fuel tank. The leaves all had circles on them where they would get sucked up to the fuel pickup. I think you have some piece of dirt that blocking a passage and settles back out after some time. Here is a little trick that may help. It will clean the carb and engine (inside). Get a can of Berrymans Chemtool B-12 at an auto parts store or Walmart. Mix it straigh with 2-cycle oil 50:1. With the tank empty, run the kitty on it straight. It won't hurt the engine but it cleans everything, even the carbon on the piston. A college auto shop teacher taught me this one for those people don't want to pay big $$$ for those quadrajet carb rebuilds. This will clean the carb and its passages but will not get rid of a big chuck that may be block a fuel passage. Good luck and let us know what you find.[/b]

Not a good idea to mix oil in the gas for a 4 cycle (ZR120).
 

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quenther

Thanks for correcting me.

I was thinking it was a 2-cycle my daughters Kitty Cat. On a 4 cycle just run it straight on the Chemtool B-12.
 

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I had the same problem. I found that the issue was in the fuel filter. Water had gotten into it and it had gone to the bowl. I cleaned the bowl and the sled ran fine for a while. Then it would die. This was when I pulled the fuel filter and found water in it also. Changed filters and haven't had a problem since.
 

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Discussion Starter · #10 ·
Well I did get it running last week after cleaning the carb numerous times, in the end I was fighting a spark plug that would fire outside the cylinder but apparently not under pressure in the cylinder. I swapped it in and out several times to verify and even with a warm motor the sled would not start with this plug in the cylinder even though it showed good spark outside.

Thanks all for all your help with this.
 

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My son's 120 was cutting out while he was riding it and it turned out to be that big tether plug. It wouldn't stay snapped on properly and kept causing it to spit and sputter and then die. I unplugged it and it runs like a top. I am going to get one of the regular red tether plugs instead of what it on there.
 
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