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Discussion Starter #1 (Edited)
I have a polaris sportsman 500 H.O. While accelerating the motor starts to break up past 5500 rpm. I changed the fuel filter. It idles and accelerates fine up to that point.
 

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have you changed the spark plug

sometimes they will break down under a load
 

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Welcome to the board!:med:
 

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I have a 2005 Polaris sportsman 400. Mine seems to develope an engine miss while accelerating also. Seems not too bad when cold and gets worse as it warms up. Idles fine. Breaks up under acceleration. Seems like ignition problem. I've changed the plug and tried another coil as the resistance was out of spec according to the manual. Just for the heck of it, I dissasembled the carb and cleaned it. No difference. I'm leaning to a stator problem or the igniter/trigger. Either that or the cdi box. The engine doesn't bogg out, it breaks up like it is misfiring. Any thoughts?
 

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Rev limiter ???

not sure what they normaly turn mine dont have a tach
 

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In the stock CDI boxes there is a rev-limiter. And as they get older the limiter is the thing that starts to go. At least it did on mine. I replaced my CDI with an aftermarket one that has a better advance curve and a higher rev limit. Almost 2,500 more than before. Plus it runs out much better and cooler also.
 

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I'm almost embarassed to admit this. I initially looked at the air filter. It looked marginal, but I could see light through it so I thought it was okay. I put on a new air filter and its a totally different bike. Here I was looking for more complicated problems and it was right under my nose. The strange thing is the bike seemed to act like the ignition was breaking down. Had me fooled, but problem is solved
 

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Had the same problem on my brothers 500. Cleaned the carb and has been fine since
 

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Glad you found it. But just to be aware, there is a rev limiter that will cause the machine to stutter and miss a litle when you get up to a certain RPM. Not sure exactly what it is set at in each machine but I can't push my 700 past 67 MPH, around 6000 RPM because it starts cutting out.
 

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I have a 2005 Polaris sportsman 400. Mine seems to develope an engine miss while accelerating also. Seems not too bad when cold and gets worse as it warms up. Idles fine. Breaks up under acceleration. Seems like ignition problem. I've changed the plug and tried another coil as the resistance was out of spec according to the manual. Just for the heck of it, I dissasembled the carb and cleaned it. No difference. I'm leaning to a stator problem or the igniter/trigger. Either that or the cdi box. The engine doesn't bogg out, it breaks up like it is misfiring. Any thoughts?
 
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