I have a 99 sportsman 500, seems it's always been kinda noisey when at idle but latly it seems to almost nock, and idle super low, but when i give it a little gas the motor sounds great, and still has all the power it's always had, is this motor going or do i just need to idle it up, little worried, almost sounds like top end don't know.

 

Not real familiar with the Polaris... usually bad noises get louder with RPM.. not quieter..Id raise the idle..

But Id also wait for some one that has one to reply...

 

A low idle knock isn't uncommon, but it also doesn't mean the motor is fine.

Are you noticing any type of metal in the oil when you change it?

 

Where does the knock seem to come from?? Could also be worn front clutch. If the buttons in the clutch are worn can cause knocking that lessens as you increase throttle. Put you ear to the clutch cover and see if noise is coming from it. Have had some that sounded like a diesel when worn! Just a thought. OPT

 

could be a loose or worn timing chain. vlaves out of adjustment as well.

 

A worn front clutch will make a terrible knock at idle but the sound will completly go away when you bring the RPM up just a little.

The vast majority of the time on a Polaris this is what you are hearing.

 

do a compression check- you'll atleast have an idea how the top end is.
might need some rod bushings or a bottom end rebuild or a clutch. There's really over a hundred things that can cause what you're describing.
polaris atv's are normally noisey- but since you've been riding it for a while, you know the typical sounds...

 

my 2000 sportsman started doing the same thing yesterday, if you figure out what was wrong could you please tell me. thanks.

 

I,d up the idle and check the clutch buttons, there a cheap part that do wear over time.

 

Ok thanks guys for all the input, i changed the oil yesterday and it didn't seem abnormal, i'll put an ear to the belt cover today, it might be the clutch it didn't get to loud until I put 27's on it, also if it was the timing chain how would i check that?