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Old 03-18-2011, 06:09 PM   #1
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accidently turned my air screw >_<

so i cleaned my carb for the first time yesterday and after i was done my bike didnt rev out rite it sputtered at the start then winded out.. so today i took it all apart again and noticed i forgot to put a spring back on near the needle, anyways i cleaned it out again and i turned my air screw by accident now i cant get my bike to start at all! Btw the bike is a 98' arctic cat 300 4x4
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Old 03-18-2011, 08:32 PM   #2
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Did you turn it in or out? Did you prime the carb?
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Old 03-18-2011, 08:38 PM   #3
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iv turned it every way now cause i took it almost fully out before i noticed it was the wrong bolt >_< and im actually not sure if its the gas or air pilot its near the 2 main jets tho under my carb >_<
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Old 03-19-2011, 07:53 AM   #4
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All screws/jets inside the bowl need to be tightened down just snug. The pilot air screw is on the outside of your carb.

Got a picture of what you're talking about?
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Old 03-19-2011, 08:07 AM   #5
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im gonna try and take a picture today, i found a thread somewhere saying the screw should be turned 3.5 to 4 turns
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Old 03-19-2011, 11:09 AM   #6
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Some of those older cats have Mikuni carburetors and the PMS screw is most likely a Air adjustment screw. On the Keihin CVT carburetors the PMS Screw is an Fuel adjustment screw.

On a Keihin Carburetor approximately 2 turns out from lightly seated would get you close enough to start the engine. Clockwise to lean, Counterclockwise to enrich the idle mixture.

On most Mikuni carburetor the PMS works opposite, Clockwise enriches the mixture and counterclockwise leans the mixture. Usually about 1 turn out from lightly seated will get you close enough to start it.

The PMS screw on both Mikuni and Keihin carburetors is adjustable for a reason because there is no particular ideal setting, Both require fine tuning one way or another to get a smooth idle and good starting characteristics in cold weather.

Idle speed adjustment and Idle mixture adjustments are always external to the carburetor float bowl for ease of adjustment and both should be adjusted to maintain smooth idle and good cold weather starting as needed.

In your case if you cannot start it at all the plug may be so badly fouled it won't start no mater what PMS setting you have it set for. I have no idea if your carburetor is a Mikuni or a Keihin either and if those base settings above and a new spark plug does not get you running you may have additional problems. Once again your engine should start and run over a wide range of PMS adjustment. It may not run smoothly until you get the PMS screw tweaked to an ideal setting open or closed from base setting maybe 1/4 turn at a time until you find the sweet spot. The sweet spot on a Keihin may be anywhere from 1 turn out to 3 turns out depending upon your engine and mods.

From what you typed I'm not sure what you adjusted was the pilot metering screw. On the attached drawing, #7 is the main jet, #8 is the Pilot Jet & #9 is the PMS adjustment screw. This is typical of all Keihin CV carburetors. Only the PMS screw and a knob for setting Idle speed is external to the carburetor. Not shown in this drawing is the Start Jet which looks identical to a main jet but has a smaller number to indicate the size. The Main jet is always located directly under the center of the slide needle where the Start jet will be off set from the center. I have no drawing on a Mikuni carburetor. Maybe another user here has an older 300 with a Mikuni that could share a picture of his carburetor and supply the base settings. If not you can probably Google it on the internet.
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accidently turned my air screw &gt;_&lt;-cv_carb_cutaway.jpg  
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Last edited by Wyo_H1_Cat; 03-19-2011 at 12:11 PM.
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Old 03-19-2011, 11:42 AM   #7
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it is a mikuni carb i just looked at the diagram and it looks like it is the gas pilot >_<

edit: i just looked at ur pic its number 9 that i turned
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Old 03-19-2011, 12:09 PM   #8
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 Quote: Originally Posted by acidburn View Post
it is a mikuni carb i just looked at the diagram and it looks like it is the gas pilot >_<

edit: i just looked at ur pic its number 9 that i turned
The picture I posted if for a Keihin carburetor not your Mikuni, For your Mikuni, Change the plug, set about 1, maybe 1-1/2 turns open from lightly seated and try it. You'll probably have to tweak the setting a little to find your ideal. You maybe able to find a service manual and default settings on the internet via your favorite search engine.

If it still doesn't start. I'd closely go over your carburetor cleaning procedure making sure it is clean as new in all ports and passageways and reassembled properly, 90% of the time failing to run properly after carburetor work is either to incomplete cleaning or improper assembly
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http://countrycat.com/ccstore/index...._Diagrams.html

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Old 03-19-2011, 06:47 PM   #9
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anyways iv turned it every what way now.. i atleast got it running but if i rev past half way it sputters like crazy then kills it..
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Old 03-20-2011, 01:31 PM   #10
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 Quote: Originally Posted by acidburn View Post
anyways iv turned it every what way now.. i at least got it running but if i rev past half way it sputters like crazy then kills it..
That would more likely be a problem with the needle or the slide not operating smoothly. Double check and recheck your reassembly of the slide and needle assembly. Make sure there is no holes in the diaphragm and is correctly sealing under the diaphragm cap. Also make sure all parts are installed in the correct orientation comparing to an exploded diagram found on one of many online vendor websites for your year and model of ATV.

The slide should operate smoothly against spring pressure when you lift it with a finger tip through the main intake throat of the carburetor and you should be able to hear the air transfer through the slides vacuum port to the diaphragm as you raise it and the closes under spring pressure.

Another possible problem is you may of swapped the Start jet with the Main jet, they look the same and they are interchangeable. The main jet will have the larger hole and the larger number stamped upon it. it is installed directly centered below the needle where the start jet is offset from center.

There is a thread called Jetting 101 in the pinned section that will increase your knowledge of carburetors and also a good cure of insomnia since it is quite long.
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Have a Problem?

Troubleshooting First Steps, An amazing number of problems are cured with just these two items.

1. Make sure your battery is FULLY Charged.
2. Try a new spark plug.

Search threads, Check Pinned Section. Pinned Topics Manual or wiring diagram? Manuals
http://countrycat.com/ccstore/index...._Diagrams.html

Improving Search.

Better results when searching for specific information. To find threads where ALL the words, instead of ANY of the words "650H1, Carb, Jetting, Needle Jet, Snorkel" were found...Open up a search window in www.google.com In the find box type without the quotes "650H1 Carb Jetting Needle Jet Snorkel site:Arcticchat.com" & Press return. Find threads, replies or topics by a specific member; just by inserting their user name into the search list; Chances are, your problem is NOT unique and it has been solved many times before.

Are you in a hurry to get an answer?
Use the Google Search Tip

Last edited by Wyo_H1_Cat; 03-20-2011 at 01:40 PM.
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