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This is my first post here. I bought a 2005 sportsman 90 for my son. It wasn't running very well when i got it. I replaced the top end, reed valve and intake tube. I also replaced the secondary jet (at least that's what i think its called, the smaller one). After that it now runs amazingly,,, for about 10 minutes, then it doesn't. I haven't been very close when it dies, but my son says that it doesn't seem to lose power before it dies, it just shuts off. It'll start right back up, either by the starter or kicking. It'll run just enough to get out of the woods and into my driveway most of the time, about 300 yards, then it usually quits again. Sometimes it'll restart after that. Sometimes it has to sit for a bit. Regardless it won't continuously run. I disconnected the oiler tube and have been running a 40:1 premix. That being said I didn't plug the oiler port on the carb, actually just thought of that, but can't imagine that would be doing this. And thoughts or trouble shooting ideas would be greatly appreciated.
 

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This is my first post here. I bought a 2005 sportsman 90 for my son. It wasn't running very well when i got it. I replaced the top end, reed valve and intake tube. I also replaced the secondary jet (at least that's what i think its called, the smaller one). After that it now runs amazingly,,, for about 10 minutes, then it doesn't. I haven't been very close when it dies, but my son says that it doesn't seem to lose power before it dies, it just shuts off. It'll start right back up, either by the starter or kicking. It'll run just enough to get out of the woods and into my driveway most of the time, about 300 yards, then it usually quits again. Sometimes it'll restart after that. Sometimes it has to sit for a bit. Regardless it won't continuously run. I disconnected the oiler tube and have been running a 40:1 premix. That being said I didn't plug the oiler port on the carb, actually just thought of that, but can't imagine that would be doing this. And thoughts or trouble shooting ideas would be greatly appreciated.
Not plugging the oil port could cause the engine to run lean and overheat especially with a 40:1 mix - you should run 20:1 mix on a cast iron cylinder - also, if the oil pump is run dry, it can seize possibly killing the engine, but more likely just stripping the drive gears and possibly having metal bits migrate through the engine.

If none of the aforementioned problems are the culprit, then fuel tank venting and ignition faults are the next likely suspects.
 

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Discussion Starter · #4 ·
Not plugging the oil port could cause the engine to run lean and overheat especially with a 40:1 mix - you should run 20:1 mix on a cast iron cylinder - also, if the oil pump is run dry, it can seize possibly killing the engine, but more likely just stripping the drive gears and possibly having metal bits migrate through the engine.

If none of the aforementioned problems are the culprit, then fuel tank venting and ignition faults are the next likely suspects.
Dang, ok thanks for the input. Since we've only run 1/2 to 3/4 of a tank hopefully that didn't screw anything up. I'll drain and remix.

What can I do about the oil pump? I will say that it does pump oil, but I feel like I shouldn't trust it?.?.? 1) should I trust it? 2) if I decide not to trust it what's the correct way to delete it and not screw anything up?

I've heard about the venting problems before and then totally ignored or forgot about it.

Thanks for the heads up! I'll plug the port, remix and hopefully someone will chime in about the oil pump delete.

Hoping it's not an ignition thing, electricity is magic to me and would have a much harder time figuring out magic as opposed to mechanical stuffs
 

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What can I do about the oil pump? I will say that it does pump oil, but I feel like I shouldn't trust it?.?.? 1) should I trust it? 2) if I decide not to trust it what's the correct way to delete it and not screw anything up?
Do you trust the oil pump in your car or truck? If you want to 'delete' the oil pump, Remove it and block off the drive (may require fashioning of a block off plate and gasket) or to leave it in place without running it dry, connect the output to the input and assure the line is filled with oil so it just recirculates.

I assure you, the oil pump is more reliable than premix as most oils will not mix with ethanol, premix must be done with non-ethanol fuel. If ethanol fuel is mixed with oil, it will cause the ethanol to separate from the gasoline within about a week and you risk running the engine on pure ethanol contaminated with water and no oil.

I've heard about the venting problems before and then totally ignored or forgot about it.
It the easiest to overlook and so simple to fix, but less obvious to observe as a problem - many times it a carb venting problem created by a ignorant previous owner. (Ignorant meaning uneducated about the construction and configuration of the vehicle).

But regardless - get the oil port capped off or plug the oil pump back into it and try to determine if it's a fuel or spark problem.
 

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Discussion Starter · #6 ·
Do you trust the oil pump in your car or truck? If you want to 'delete' the oil pump, Remove it and block off the drive (may require fashioning of a block off plate and gasket) or to leave it in place without running it dry, connect the output to the input and assure the line is filled with oil so it just recirculates.

I assure you, the oil pump is more reliable than premix as most oils will not mix with ethanol, premix must be done with non-ethanol fuel. If ethanol fuel is mixed with oil, it will cause the ethanol to separate from the gasoline within about a week and you risk running the engine on pure ethanol contaminated with water and no oil.



It the easiest to overlook and so simple to fix, but less obvious to observe as a problem - many times it a carb venting problem created by a ignorant previous owner. (Ignorant meaning uneducated about the construction and configuration of the vehicle).

But regardless - get the oil port capped off or plug the oil pump back into it and try to determine if it's a fuel or spark problem.

i have no idea how to set up different lines of quotes..

the "Do you trust your truck, thing?". Honestly never thought about it that way. All the info you shared about what happens with a pre mix i was completely unaware of. Not to mention correctly getting rid of the thing is so much more work than i was expecting to hear. So back to the oil pump it is.

So between air venting into the tank and possibly running lean because the oil port is open I've got a few good culprits to trouble shoot and hopefully fixes the issue.

Seriously thanks for the advise. Really helpful and hopefully I'll get this thing running correctly for my kid.
 

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I have a degree in electronics and was writing computer programs back it the 70's - there are some things I can manipulate that others can't, but my grandsons can show me things I don't know - they are no longer programming in Cobol, Fortran and Basic - it's now done in packets and each packet may be written by a different person then the whole thing compiled and debunked - it's all Greek to me, but they are baffled by DOS
 
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