ATV Carburetor Help - Kawasaki ZX-10R.net
 
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post #1 of 6 Old 09-20-2010, 08:37 AM Thread Starter
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ATV Carburetor Help

It's been a while since I posted here but I figure that there has to be some experts here on vintage 2 strokes. I have recently become the proud owner of perhaps the most aesthetically pleasing ATV model of all time, the 1987Polaris Cyclone 250. I'm not completely ignorant of the ways of the carburetor, but I don't know where to go from here with this one. It is a Mikuni but there are no numbers on it, it just has MIC on each side. The engine will start and run if you hold the throttle at about 1/4. It will rev up with some slight bogging. When you rev it up, a mist of gas blows out the carburetor (obviously I have the airbox off). It will not idle unless you hold the throttle. I have cleaned it including all the circuits and lowered the float level to no avail. the only adjustments are what looks like an air screw on the carb and the notches on the needle, bot hof which I have messed with. I would love to hear any Ideas as to what might cause this behavior and how to fix it.
I forgot to add that when I shut off the fuel, It revs way up just before running out of fuel in the line/bowl.

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Last edited by BrockLanders; 09-20-2010 at 08:53 AM. Reason: Additional info
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post #2 of 6 Old 09-20-2010, 08:57 AM
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Maybe a clogged pilot jet? I'm not familar with your ATV so I'm not sure if your carb has one. Since you didn't specifically mention it, I'm pointing it out.
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post #3 of 6 Old 09-20-2010, 09:35 AM
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Quote:
Originally Posted by Colinr_69 View Post
Maybe a clogged pilot jet? I'm not familar with your ATV so I'm not sure if your carb has one. Since you didn't specifically mention it, I'm pointing it out.
:iamwithst maybe a low speed jet??? becuase you say it runs better with the throttle crack the high speed jet can be trying to take over at that point feeding fuel. You might also wanna check your reed valves??????

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post #4 of 6 Old 09-20-2010, 09:45 AM Thread Starter
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Thanks for the suggestions. I will re-check the pilot jet. I thought it was clear but who knows? The engine is a piston-port type so there are no reeds. It would make sense that the mid range circuit is taking over and the pilot circuit is not functioning at all.

But I have done a thousand dreadful things,
As willingly as one would kill a fly,
And nothing grieves me heartily indeed,
But that I cannot do ten thousand more.
-Titus Andronicus
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post #5 of 6 Old 09-23-2010, 07:48 PM
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take the bowl off the carb, pull out every jet, remove the float, pull out the rubber tipped needle, and use a straw with carb cleaner and spray every vessel u see. If i remember right, mikuni uses round jets apposed to kehin hex jets. you should be bale to see through the jet when its clean. also, check the end of the rubber needle and make sure it isnt dry rotted torn up, it should be pretty pointy. if still no luck, it may just be jetted wrong. Look around online and see what the stock jeetin it came with. temperature, humidity, and elevation will all play a roll in your jetting. should just be a main and pilot jet, and i doubt it has an adjustable needle.

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post #6 of 6 Old 09-27-2010, 12:44 PM Thread Starter
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Thanks for the replies! After thoroughly cleaning and inspecting everything for the umpteenth time it still didn't run right. I found a used carb locally for $50 and now it runs great.

But I have done a thousand dreadful things,
As willingly as one would kill a fly,
And nothing grieves me heartily indeed,
But that I cannot do ten thousand more.
-Titus Andronicus
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