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Discussion Starter · #1 ·
Idles fine, runs great up to full throttle.....as soon as I put the boot on the back of the carb it bogs from 1/2 throttle and up.....no air box, no air filter, just the rubber boot. I'm trying to get it to run with the air filter....any ideas?
 

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Ball Automotive lighting Vehicle registration plate Font Gas
 

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Please let us know just what we are working on??? Car, Chainsaw, Outboard motor or what year and model of ATV....
Gas Font Heat Pattern Event
 

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Discussion Starter · #4 ·
First time here, sorry. It's a 1999 polaris magnum 500. I Think it may be running too rich, can I lean it out with the pilot screw or do I need to change the main jet, or mabie lower the needle?
 

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Your question has now been logged into the queue and the next available forum member will answer you shortly. Welcome!
 

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2004 Sportsman 700, 2004 Scrambler 500, Various Others.
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Use the air/fuel adjustment screw and needle first and when they are maxed out you change jetting and get your adjustability back.
 

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Thanks, will start with the pilot screw first
The pilot screw is for idle only - it is for all intents and purposes not functioning above 1/8 throttle - the slide needle is for 1/4 to 3/4 throttle and the main jet is for wipe open top end only - I kinda agree with Oldhunter1 that the slide may not be moving as designed with increase in throttle opening, but if it doesn't bog with the air cox connected, it's too rich anyway.

What size jets are in it now?
 

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Discussion Starter · #11 ·
I believe most of the problem is with the diaphragm, I took it apart, didnt see anything that jumped out but after I put it back together I noticed the slide wouldn't even move until it was at full throttle. I could only get full throttle without the air intake boot still.So at the end of the day, I made it worse, now it has no power until it is wide open....I have a carb kit ordered, cant wait until it arrives. I made sure the diaphragm was seated correctly when I put it back together, I don't understand why it is acting worse.....lol
 

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Thanks again for your thoughts
Had a similar issue with my son-in-laws 335. Even though I know them top to bottom, I opted for an aftermarket, and made sure the pilot jet and the main were correct. Good luck, make sure the cutout is toward the air box.
 

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2004 Sportsman 700, 2004 Scrambler 500, Various Others.
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None. Rebuild what you got. Chinese junk is all you’re gonna get from sites like eBay and Amazon.
 

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If the slide is a problem, you will find a tear or pin hole in the diaphragm - having the carburetor cleaned and rebuilt by a competent mechanic may be all that is needed to solve the problem. The internal vacuum passage that causes the slide to rise may be clogged or there may be a restriction to free movement due to a worn slide or jet block, but rebuilding the quality Mikuni is preferable to installation of a Chinese counterfeit. Avoid all Chinese carbs, but if a Chinese carb is your choice get a KunFu, Standard of Japan or CVK.
 
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