I just took the air filter off of it and it runs wide open great - I don't get it ? not getting enough air ? Geesh I'm not real knowledgeable about this but I love working on it ! Retired and have all the time in the world !

 

Too much fuel - a 145 main jet is correct - your experience is just why I don't buy "kits" - I take the carbs apart and just get the parts that are needed. Put the 145 main jet in and it will probably run right with the air box lid on.

 

Thanks for the reply latebird !
I did actually put the new 145 main jet from the kit in it but didn't replace the old jet needle, I just cleaned it up real good and put that back in.
Do you think my problem revolves around that main jet (high speed jet)? How else can I get more air to the carb? air/fuel mixture screw ? I know these are dumb questions for most of you. Live and learn :grin

 

For the record there is no air/fuel mixture screw. The one in the front of the carb is an air bleed screw. Set it to the factory spec and leave it alone. Where is your jet needle set and what pilot jet is in it? You are obviously over fueled now just have to figure out why.

 

Thanks for the reply Stave 7119 and thanks for the correction on air/fuel mixture screw - that is set at 2-1/2 turns.
The jet needle was set at the 2nd groove from the top so that's where I left it. The new pilot jet I installed from the kit is a 50. Hope that helps ?

 

The pilot jet and fuel screw are to set the idle mixture - the initial setting on the pilot screw is 2 turns out from lightly seated - with the engine at normal operating temp - adjust the fuel screw for the smoothest idle.

The mid-range (1/4 to 3/4 throttle) is controlled by the slide needle - run the machine at about 1/2 throttle - if it blubbers (too rich) drop the needle (raise the clip) one groove - if it surges or just seems to loose power (too lean) raise the needle (lower the clip) one groove. Run again and adjust again if necessary.

Once the idle and mid-range are set, run at full throttle (air filter in, lid on, snorkel on - whatever the normal operating configuration is going to be) - it should accelerate cleanly all the way to the rev limiter - if it blubbers (too rich) use a smaller main jet - if it never gets to the rev limiter or just looses power and won't accelerate any more (too lean) go bigger on the main jet.

Each change may affect the other circuits slightly, so adjustment of idle and mid-range may be necessary for changes in the main jet or other circuits.

 

The only thing I will add to that is to check the jet needle style/model. The size and shape of the pointed end can make a difference so you want to make sure you have the right one for your carb. It should be marked (really teeny letters)

 

MODEL: . . . . . . . . . . MAGNUM 325

CARBURETION
Type . . . . . . . . . . . . . . . . BST 31 Mikuni
Main Jet . . . . . . . . . . . . 145
Pilot Jet . . . . . . . . . . . . . 50
Jet Needle . . . . . . . . . . . 5F14-3
Needle Jet . . . . . . . . . . . P-2(829)
Throttle Valve . . . . . . . . #120
Pilot Screw . . . . . . . . . . 2 Turns Out
Pilot Air Jet . . . . . . . . . . 175
Valve Seat . . . . . . . . . . . 1.5
Fuel Octane (R+M/2) . 87 Non-Oxygenated or
89 Oxygenated

 

I most certainly appreciate you guys expertise ! That's alot of great info. !
I wondered about the needle sizing because I put the new main jet 145 in it then cleaned and left the original needle that fit to the original 120 jet that was in it before rebuild? hmmmm ? cause'n problems there ?
It idles fantastic and can rev it to about 1/4 then it chatters with air filter on so looks like I'll be taking the carb back off and use this info and get it figured out. I like a good challenge !
Latebird - Thanks for the spec.'s - I've seen 2 different spec.'s on carburetors for 2002 325 Magnum. The one below is from my 2002 Polaris Magnum 325-500 Service Manual and looks like there are some minor differences ? main jet, jet needle, turns
MODEL: 2002 MAGNUM 325 ..........
MODEL NUMBER: (2x4’s) A02CB32AA/FC - (4x4’s) A02CD32AA/AB/FB . ENGINE MODEL: ES32PFE08 ..
CARBURETION Type BST 31 Mikuni.......................
Main Jet 120 ...................
Pilot Jet 50 ....................
Jet Needle 5F14-2 ..................
Needle Jet P-2M(829) ..................
Pilot Screw 2-1/2 Turns Out .................
Pilot Air Jet 175 .................
Valve Seat 1.5 ..................
Fuel Octane (R+M/2) 87 Non-Oxygenated or ........
89 Oxygenated

 

I was using a manual that covered multiple models - I did not know which of the 6 models offered that year you are working on. I just selected one and offered information based on what I read. Use the information you have in your manual. It is probably more correct than what I offered.

 

Ok sounds good - thanks again for your help - I'll keep ya posted as I go.

Uncle Dave

 

Ok.....All the 325 machines used the BST31 carb. Pilot jet will be the same but the main jet is different as is the main jet needle. So you have 2 choices, you can change the main jet back to the 120 with the same jet needle, or change the jet needle to the one from the kit that should mate up with the 145 main jet.

 

You just confirmed what I was thinking of doing Stave - greatly appreciate that info. I'll be putting the original jet 120 back in, it's all cleaned up.
I'm going to get started on it tomorrow morning after my grandson and I get my deer stand up and will give the lowdown tomorrow afternoon on how it runs. Thanks again !

 

I put the old 120 main jet back in, attached gas tank & air filter. It fired right up - idles great. It opens up well to about 7/8 throttle and when I gun it wide open it chatters. When I remove the air filter it opens wide open no problems.
I use this ATV for hauling deer, decoys & checking traps and never run it more than 1/2 throttle anyway so to me it's good to go. If I wanted to figure out the full throttle chatter problem, I'm guessing I would change the needle clip groove placement?
Thanks for all of the help !

Uncle Dave

 

Smaller main jet or new air filter - the slide needle is for about 1/4 to 3/4 throttle settings when the throttle is held at a steady state

 

Air filter is brand new so smaller main jet would be my next move - Thanks latebird !
I'm going to put it back together knowing it will work well for what I need it for and maybe late winter dig into it again.
I really enjoy working on it so it's all fun for me ! ! It will be a lot nicer if I can get a deer and some waterfowl in my freezer.
Thanks again !

Uncle Dave

 

OK everybody can use a good laugh for the day - I have a left over part - big rubber gasket for ? flange is 3-3/4" O.D. and I.D. is 2-7/8". There's about a 3/4" lip that a hose clamp fits on. Thought it came out of the air-box ? Looked all over for it on parts diagrams. It says R0070 and 3-20-11 on the rubber flange. My old memory is shot ta pieces !:| I don't know how to down load jpegs.

Uncle Dave

 

It was the rubber end off my old air filter - HAAAAA ! I gotta laugh or I'd go crazy-er !

 

Taking the filter off and runs fine means too much fuel not enough air id say ur main pilot is too big once vacuum is created