1998 polaris sportsman 500 problem

[jonesin]

I have a 1998 polaris sportsman 500 that has a issue.
When I am just riding around, plowing snow, working, pulling trees, wagons, whatever, it runs fine but if I run down the road or across the field at faster speeds it will suddenly loose power and die. I can sometimes feather it and keep it running or wait a minute and start it and it will run fine at lower speeds but the same thing will happen again going faster.
A year or so ago, I cleaned out the gas tank, checked lines, replaced the fuel pump, fuel filter, put in a new needle and seat, cleaned the air filter and it seemed somewhat better but never completely left, and now it is back again.
I was pricing a new air filter system, since it is probably original and I just clean it occasionally but it doesn't look bad.
I was messing around with it last night, (chasing a pony that got out of the pasture), and I had the side cover off so I could see the fuel filter, it looks empty, only a steady "mist" when running, when shut off it will fill up half way. Is that normal? I would have thought that it would be full of fuel.
It also smelled hot last night, but there isn't any coolant leaks that I can find, could it be a cracked head or something?
Any ideas would be helpful.
Thanks.

 

[briano]

Is the fuel filter on backwards, I just bought a Suzuki quad racer that was doing the same thing and the guy before me could never get it to run right either, come to find out the filter was on the wrong way, flipped the filter and runs perfect. Or the main jet could be plugged, when just putting around you are not using the main, you are using the pilot jet, then when you get on the throttle it needs more fuel through the main jet. Check the filter and clean carb and jets and you should be good.

 

[jonesin]

I'll check, but I am pretty sure that it's right.
Does the fuel filter being empty sound right?
Thanks.

 

[booondocker]

I'll check, but I am pretty sure that it's right.
Does the fuel filter being empty sound right?
Thanks.

NO it does NOT!

That's the problem no doubt.

Is there a fine screen mesh screen in the tank at the fuel shut-off?

Is there something in the fuel shut off that could be causing this (take it out and check it)

That is a gravity feed, so it should be full all the time.

Also running at slow speed shows that you can "live with" the small amount of fuel being delivered, but at faster speeds, you are starving the engine. This is consistant with a plugged fuel filter or lack of fuel.

 

[jonesin]

As I said, I had the tank off and took apart and cleaned everything I could find on the tank and carb.
It has to be something blocking. I was going to see if there is a breather tube to the tank under the shroud and check if its plugged not allowing it to breathe.
Last night I was looking at it and it would be real easy to by-pass the fuel pump altogether. The fuel lines go from the tank to a switch for on-off-reserve. From there to the fuel pump (that I replaced last time) and from there to the fuel filter, I could run the line from the tank to the fuel filter directly and bypass the switch and pump and see if gravity alone works correctly.
Thanks for the input!

 

[booondocker]

Good plan...

It is possible that the fuel pump you put in new...isn't working right. But the fuel filter should be full or at least 1/2 full.

By-pass the fuel filter once to see if that is the issue, as well as the pump, and if the tank isn't letting fuel out fast enough, loosen the cap when it starts acting up and see if that improves the issue.

 

[jonesin]

cracking the gas cap open didn't work.
if it ever stops raining i'll try re-routing the gas line next.

 

[jonesin]

cracking the gas cap didn't work
if it ever stops raining i'll try re-routing the fuel line

 

[huntdiamondjim]

does your machine backfire at all? i have a 99 sportsman 500 and the cam shaft wore out. the camshafts in 98 and 99 were made a little soft this is a relative common problem with them. the exhaust lobe wore down on mine. machine would run but would not have any speed or power. if you go to a atv site you should be able to find some info. good luck jim

 

[rp7x]

soft cam

my 97 lost the ex lobe also

 

[ubee]

x-3

 

[snowfish]

I had the same issue with a 700 Sportsman last summer. The carb needed to be cleaned. And I mean every little frog hair jet & passage. I finally got it the third time around. (always good to do things two or three times! LOL!) Be sure to carefully push a wire through each jet & passage. Even the ones that you can see light through. Varnish can be quite transparent. Then blast carb cleaner through everything, to the point of chapped hands. Dry with compressed air, but hang on to the little jets for dear life. (kind of hard to find, when they rocket out of your fingers, across the garage floor.)

I too experience the woes of the wrong filter or backward filter. Needs to be the right one in the right direction.

I would never run on reserve, unless absolutely necessary, since it does not have an in tank filter screen. I discovered that on my third time around. The main is elevated with a screen on top. The reserve is a straight shot off the tank bottom.

Your fuel pump is probably fine. Really not much to them. My final last ditch effort was to remove, disassemble, & clean the tank. (more crud than I thought was hiding in there) Clean the fuel shut off, back flush the new filter, and really, really clean the carb for the third time. Now it takes larger nads than I to hold it WOT for any extended periods of time.

One final note...........Your carb may have a vacuum activated slide. You'll know when you tear it down. The 04 700 Sportsman did. If the slide can spin around, it's disconnected from the bellows. It will need to be replaced.

 

[jonesin]

No backfiring, its starts and runs great, plenty of power, absolutely no complaints except at higher speeds.

The lack of fuel visible in the filter is what has me curious and I would like to resolve first. I was giving my 2 yr old a ride the other night and just putting around the yard I could see the filter was basically empty, not much liquid visible, just a steady fine mist which just doesn't seem right.

Thanks for the ideas!

 

[briano]

The filter not being full is strange, but I have put inline filters on a few of my quads and that is how mine were too. It seems they should fill with gas but sometimes they don't, I tried to take the line off of the carb and let the filter fill up and then put the line back on, start the motor and the filter would be empty again. I never had a problem with the way my quads ran it was just strange that the filter wouldn't stay full

 

[jonesin]

briano,
well that is interesting...
if that is normal then i would be back to re-cleaning the tank, carb and shut off switch.
thanks for the info!