I have a 1997 Polaris xplorer 400 (2-stroke atv). It won't rev out all the way. It's like it hits a wall at a little over 3/4 throttle and then just won't rev out... I cleaned the carb thoroughly, jets are clear and I checked the sizes against the chart in the operator's manual, set airscrew, have a clean air filter, am getting fuel/oil... I also opened the clean outs on the exhaust pipe and ran it... they are clear. I'm not sure what else to check. Could a reed cause this? It idles perfect and works well in low to mid rpm running, but I can tell it lacks power and then it won't rev out. Please help I just got done going through it and really want to get it running right. Thanks in advance!

-Wes

 

Sounds like it could well be a clutch issue. Does it do this while in neutral if you rev it or just in gear or both? I'd jack it of the ground, pull the clutch cover and run it, check to see if the clutch is hanging up.

 

It does do it in neutral, as well as in gear. Does this rule out the clutch?

I figured fuel system or ignition, but I don't know for sure. I definetely don't know it all when it comes to diagnosing performance issues on atv's [img]i/expressions/face-icon-small-smile.gif[/img]

any other ideas? Thanks again [img]i/expressions/face-icon-small-smile.gif[/img]

 

i would get new reeds for it.it may not be causing the problem but it wont hurt either.
have you checked the spark plug?
is the gas fresh?
how about the counter balance oil and transmission oil?

 

If it's doing it neutral as well you can probably scratch the clutch idea. I'm not much on carb issues...I'm sure before long you'll get lots of good replies from these guys, they can usually pin down a problem pretty quickly. Good luck

 

sounds like your slide in your carb is not going up all the way or something along those lines.

 

not sure if yours have it.on the bottom of the thumb lever there is a slide that limits the throttle.loosen the screw and mash the thumb lever all the way. it could give you more throttle

 

It is not the throttle stop for sure. I can go past where it starts to bog on the top end with the throttle lever before it mechanically stops. If I back off of the throttle about 1/8 travel, it stops bogging. It's just at the very top of the rpm range.

The spark plug is near new, I changed out the fuel filter last night with no change. The air filter makes no difference whether it is installed or not.

I decided to see if it was a lean condition so I dropped the clip position on the needle to raise it and richen it up a little bit, but that seemed to make it worse. I will do the opposite tonight to see if maybe it's a rich condition problem.

I have to check the oil pump to see if that is correctly adjusted too. If all of that doesn't work, I'm going to drain the fuel and clean the fuel petcock screens. If those are gummed up, it would create a lean condition no matter what I do at the carb.

Any other ideas? Please keep them coming... I need to track this little gremlin down and get it running right by the weekend if possible [img]i/expressions/face-icon-small-smile.gif[/img] Thanks again [img]i/expressions/face-icon-small-smile.gif[/img]

-Wes

 

Maybe I didn't describe the problem quite right... Let me clarify. When I run the rpms up, at about 3/4 (a little bit above) throttle or so, it bogs and won't rev out. The throttle goes past that point, but the rpm's don't increase. That's why I said it was like hitting a wall. When I back out of the throttle a little but it smooths out, but I just can't get it to rev beyond that point. Whatever the problem is, it is also affecting power/throttle response slightly thoughout the entire rpm range.

Oh yeah, all of the fluids and levels are good. I just changed everything and checked levels just yesterday. Trans, counterbalance, coolant, fuel. There was a little old fuel in the tank, but I poured fresh in there and I would say that the little bit of old gas (about 7mo old) was not enough to sour the fresh I put in. If it was bad gas, I can't imagine it would run as well as it does at least up to the point where it bogs...

Also, the carb and all components are in good working order. The slide doesn't stick in the bore and I can run the throttle past the point where it bogs. It travels like it should and all jets are clean, needle is in good shape. I'm pretty sure the carb is not the issue. It is set perfect (except for my experiment last night with the needle jet, but will change back) according to the book and everything is in good shape and clean.

Please keep the ideas coming. Thanks again [img]i/expressions/face-icon-small-smile.gif[/img]

 

remove carb and reed block and cage, look at piston skirt, see if the skirt is broken. if it is, crank pressure is pushing your fuel and air charge right back out the crankcase, skirt can't close the cylinder off.