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Discussion Starter #1
Hello,

I have an arctic cat 300 4x4 red ATV, which starts fine and can stay idle for hours, but when I push the throttle (giving gas...) it dies...

First I tried to adjust my valves - no change.

Then I opened my carb, found out the diaphragm was worn, replaced it along with the main jet, pilot jet, pilot air screw, and valve seat, all genuine new parts.

After cleaning and reassembling the carb I tried to tune the pilot air screw, finally set it back to the the recommended 2.75 turns, but still has the same problem...

Any ideas what else can cause it?

Thanks,
Omer.
 

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Any difference if you apply some choke while applying throttle? If that helps, you need to richen it through the needle by raising it either by lowering the e-clip or adding a shim.
 

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Discussion Starter #3
Sometimes it helps, sometimes it doesn't... anyway I don't think I need to richen it because black smoke is coming out of the exhaust at about 1/2 throttle...
 

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The factory setting for the fuel screw (North America anyway) is 2 1/4 turns out. Try turning yours in to that setting, or a bit more to 2.
I don't like suggesting this, but for a quick test, remove the air box lid, remove the (I'm assuming clean) air filter and re-install the lid. Better or worse?
 

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Does it die instantly when you hit the throttle? Can you go into a little more detail about how it goes about dying when you give it throttle? Will it start right back up?
 

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Discussion Starter #6
The factory setting for the fuel screw (North America anyway) is 2 1/4 turns out. Try turning yours in to that setting, or a bit more to 2.
I don't like suggesting this, but for a quick test, remove the air box lid, remove the (I'm assuming clean) air filter and re-install the lid. Better or worse?
You mean the air screw? I couldn't find a fuel screw in my carb... I tried tuning the pilot air screw from about 2 turns to 3 1/2, and the best results was in about 2 3/4.

the air filter is also new, though removing it did not change anything..

Thanks anyway

CumminsDriver said:
Does it die instantly when you hit the throttle? Can you go into a little more detail about how it goes about dying when you give it throttle? Will it start right back up?
Yes, it dies instantly when I hit the throttle, sounds like it is choking at some point, but as I mentioned sometimes it passes this point and then it can run on high rpm until I leave the throttle, and then it dies again.. usually it starts right back up after that happens.

Also if I may I have another question about the carb - after I assembled it again it started leaking a little from the float chamber - seems like it is leaking from the gasket. from what I understand there should be no fuel at that level as the valve should stop the flow, so it doesn't matter what the gasket condition is while the ATV is standing. the valve seat and needle are new, and the float seems to move freely, what can cause this leak?

Thanks for the help meanwhile I dunno
 

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OK, the engine issue might possibly be the rectifier/regulator causing the problem.

For the leaking fuel, be sure the carb's bowl is seated tightly, screws are good and snug. Be sure the fuel tank vents freely and is not pressurizing.
 

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Discussion Starter #8
Is there any way of checking the regulator without replacing it? it seems ok, and there is a good spark...

about the carb - the bowl o ring is dry, I ordered a new one, hope it will help.

Thanks.
 

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Sounds like a choke issue to me. Have you looked at that yet?
 

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Discussion Starter #10
When I disassembled the carb I tried to understand what exactly the choke cable does to actualy choke, with no succes, so I really don't know if the choke is ok or not...

Anyway I think I will disassemble the carb again to make sure everything is ok there - I will be very happy if someone will explain me about the choke.
 

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Discussion Starter #11
Solved.

Carb was re-cleaned and almost all the inside parts was replaced (most of them looked terrible), now works like new.

Thanks for all the help.
 

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When I disassembled the carb I tried to understand what exactly the choke cable does to actualy choke, with no succes, so I really don't know if the choke is ok or not...

Anyway I think I will disassemble the carb again to make sure everything is ok there - I will be very happy if someone will explain me about the choke.
This should explain how it works for you. Also some additional info concerning the jetting for either you or others

The choke on arctic cats comes in two flavors. Either automatic electric or cable actuated. The choke does not choke off air flow as your common choke does. It is an enrichener. It is a electrical or cable controlled valve that dumps in extra fuel into the engine through the "start jet". one of the three jets screwed into the underside carburetor body. The start jet is the jet that looks just like the "main jet" and will interchange with the main jet if the carburetor is assembled wrong during assembly. The start jet has a smaller orifice than the main jet though. To identify the main jet location it is directly below the needle. the start jet is the jet that looks like a main jet and off to the side. The third jet is the slow jet or sometimes called the pilot jet that is smaller in diameter and down in the hole.
 

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So I have the same problem except it wont pass a certain rpm and run. It just dies instantly. I tried rebuilding the carb and that didnt chance anything. So I installed a brand new one ?. Still no change. Please help.
 

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I’m having the same problem starts idles fine as soon as I give it gas it shuts off I cleaned the carburetor put a new coil and wire set my valves and still the same thing checked my fuses and took the wiring harness appart everything looked fine so I put silt back together and tried it again still the same problem any help at all would be appreciated thanks
 
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