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Discussion Starter #1
I recently picked up a 2003 Polaris Sportsman 700 Twin 4x4. It starts and runs decent, but around 40ish mph it starts to hesitate. Also, when slowing down, it sounds like it is backfiring however I hear it at the from of the engine. I have a new set of exhaust gaskets and springs coming this week. What should I check as far as the hesitation? I figure the hesitation and backfire are linked to a carburetor fuel issue. I did replace the spark plugs with two new ones, did not change anything.
Thanks in advance,

Kyle
 

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What fuel are you using? Brand, octane, % of ethanol?

I believe you are on the right track - it's a fuel, carb or air filter issue.
 

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Discussion Starter #3
What fuel are you using? Brand, octane, % of ethanol?

I believe you are on the right track - it's a fuel, carb or air filter issue.
I am running 87 octane, not sure of the exact brand or % of ethanol. However, I have used fuel from this station(Murphy Express) for all of my machines (including my old 2002 700) and never had issues.

I am wondering if I need to move up a main jet size. Previous owner had fuel screw (or whatever it is called) to 3 turns out. I really don’t want to turn it out more than that. I have no idea what jet size is in there now as I have not been into the carburetor yet
 

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Polaris calls for 87 octane (89 if 10% ethanol) - I just run 91 octane non-ethanol in my vehicles

Fuel screw is for idle only - it will not affect running over 1/4 throttle

Some brands of fuel may contain more or less than 10% ethanol - ethanol absorbs water so buying ethanol blended fuels equates to buying a certain amount of water - water will cause ethanol to fall out of the gasoline (phase separation) - in vehicles not used daily the separation is more prevalent - alcohol blended fuels have a shelf life of 100 days in closed containers and about 25 days in open containers (a fuel tank is an open container) - ethanol fuel should be disposed of every three weeks
 

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Discussion Starter #5
Polaris calls for 87 octane (89 if 10% ethanol) - I just run 91 octane non-ethanol in my vehicles

Fuel screw is for idle only - it will not affect running over 1/4 throttle
I’d like to be able to run ethanol free fuel but there isn’t a station anywhere close to me unfortunately.

My point with the fuel mixture screw is generally, turning out makes it richer and in makes it leaner, and on every other machine I have had if it pops on decel it is a lean condition and should be fine tuned by backing that screw out a little at a time. My concern is that it is already 3 turns out, so wouldn’t that be time to go to the next size main? and then retune the screw when the new jet is in place to try to eliminate the popping on decel?
 

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Discussion Starter #6
Well, found the problem causing the backfire!
The front exhaust donut seal (or whatever it is called) was completely gone. Replaced all exhaust seals, now way quieter as you can imagine and no more backfiring.

However, it is still hesitating around 45 mph (GPS speed). Is this the normal top speed of Sportsman 700's?
 

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Well, found the problem causing the backfire!
The front exhaust donut seal (or whatever it is called) was completely gone. Replaced all exhaust seals, now way quieter as you can imagine and no more backfiring.

However, it is still hesitating around 45 mph (GPS speed). Is this the normal top speed of Sportsman 700's?
Nah, it should run about 60+
Worn belt and tired clutches will cut top speed as will some clutch kits.
You may have carb or other issues if the engine is falling off on top end and limiting speed.
 

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Discussion Starter #8
Well, found the problem causing the backfire!
The front exhaust donut seal (or whatever it is called) was completely gone. Replaced all exhaust seals, now way quieter as you can imagine and no more backfiring.

However, it is still hesitating around 45 mph (GPS speed). Is this the normal top speed of Sportsman 700's?
Nah, it should run about 60+
Worn belt and tired clutches will cut top speed as will some clutch kits.
You may have carb or other issues if the engine is falling off on top end and limiting speed.
That's what I figured.
The more I ride it, the more it reminds me of hitting a rev limiter. Did a little reading and read how sometimes a nut backs off the clutch and causes this same issue, with about the same top speed. Will pull it apart this weekend and take a look, I hope it is that simple.
 

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Discussion Starter #9
Solved! The nut had backed off the clutch. Snugged it back up and it is hitting 55ish before I run out of road and still climbing.
 
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