Polaris ATV Forum banner

1 - 4 of 4 Posts

1 Posts
Discussion Starter #1
I replaced my carburetor on a 2004 polaris predator 50cc. Like a dummy I had the fuel line running to the overflow and it ran but it would obviously flood out.. Now that I have everything connected right, it doesn't want to stay running. I have a video of what happens when it starts and dies. It is a brand new carburetor and I started fiddling with the two screws on the side air and fuel? I cannot get it running long enough to try to adjust anything any help would be appreciated... It does have good gas in it as well.

Video link

Premium Member
20,001 Posts
Welcome to the board!

2,959 Posts

NOTE: Adjusting the air screw can affect idle speed.
Always check throttle cable freeplay after adjusting
idle speed and adjust if necessary.

1. Turn carburetor air screw in (clockwise) until lightly
seated. Back screw out the specified number of

Air Screw
Air Screw Adjustment:

50 cc: 3/4 Turn Out from Lightly Seated
90 cc: 7/8 Turn Out from Lightly Seated

2. Warm up the engine to operating temperature
(about 10 minutes).
3. Set idle speed to 1200 RPM.
4. Turn the screw in (to richen) or out (to lean) the
mixture. Adjust air screw for best throttle
response and smooth idle.
5. Re-adjust idle speed to 1200 RPM if necessary

2,959 Posts

Symptoms: Hard start or no start, bog, backfire, popping through intake / exhaust, hesitation, detonation, low
power, spark plug erosion, engine runs hot, surging, high idle, idle speed erratic.

No fuel in tank
Restricted tank vent, or routed improperly
Fuel lines or fuel valve restricted
Fuel filter plugged
Carburetor vent line(s) restricted
Plugged or restricted inlet needle and seat screen or inlet passage
Clogged jets or passages
Float stuck, holding inlet needle closed or inlet needle stuck
Float level too low
Intake air leak (throttle shaft, intake ducts, airbox or air cleaner cover)
Jet needle position incorrect
Incorrect pilot screw adjustment


Symptoms: Fouls spark plugs, black, sooty exhaust smoke, rough idle, poor fuel economy, engine runs rough/
misses, poor performance, bog, engine loads up, backfire.

Air intake restricted (inspect intake duct)
Air filter dirty/plugged
Choke plunger sticking, incorrectly adjusted choke
Choke cable binding or improperly routed
Incorrect pilot air/fuel screw adjustment
Faulty inlet needle and seat
Faulty inlet needle seat O-Ring
Float level too high
Poor fuel quality (old fuel)
Loose jets
Worn jet needle/needle jet or other carburetor parts
Dirty carburetor (air bleed passages or jets)
Fouled spark plug


Symptoms: Idle too high.

Idle adjusted improperly/idle mixture screw damaged
Sticky throttle valve
Throttle cable sticking, improperly adjusted, routed incorrectly
Choke cable sticking, improperly adjusted, routed incorrectly


Choke cable incorrectly adjusted
Idle speed set incorrectly
Idle mixture screw misadjusted or damaged
Belt dragging
Ignition timing incorrect
Worn jet needle/needle jet


Choke cable bending or incorrectly adjusted
Throttle cable incorrectly adjusted
Air leaks, dirty carburetor passages (pilot circuit)
Pilot mixture screw damaged or adjusted incorrectly
Tight valves
Ignition timing incorrect
Belt dragging
Dirty air cleaner
Engine worn
Spark plug fouled
Idle speed set incorrectly (speed limiter)
Worn jet needle/needle jet
1 - 4 of 4 Posts