1999 Polaris Sportsman 500 loud and no power

[luckyhook]

I have 1999 sportsman 500 that starts fine but when you give it gas gets loud and has no power under load.. What to check?

[Ajmboy]

Sounds like you may have an exhaust leak. Or is it an engine noise?

* Added manufacturer to your thread title and full year.

[luckyhook]

It does sound like a worn out muffler, is there a way to test for this before pulling it apart?

[mat1994]

maybe your belt could be slipping...

[MUDDIE49]

Yeah i was going to say check the belt....

[luckyhook]

Pulled the exhaust sytem yesterday and do not see anything obvious, no cracks or leaks, I opened the drain on the spark arrestor and very little carbon came out. Going to change plug, Didnt put in a ngk when i changed in spring as dealer only had a A.C. replacement. So I got a ngk and will try that too.

I dont think the belt is slipping, on a limited budget so dont want to bring into a shop if I can help it.

[Ajmboy]

It does sound like a worn out muffler, is there a way to test for this before pulling it apart?

Take a rag or old towel and place it over the exhaust outlet to muffle it...backpressure will build and you should be able to hear if there is an ehxaust leak.

[DirtDemon]

I would check the valve lash, vavle timing and ignition timing. Since it is not likely that the ignition timing is just going to change, if it checks bad, it most likely is because of a sheared flywheel key.

[luckyhook]

I took off gas cap and gas did not smell good so I decided to pump out old and put in some new. Now It seems to be not so loud but is backfiring when i give it gas, i ran it for 10 to 15 minutes to see if it would clear up but sytill had no power and is now backfiring, Could this be something in carb?, Is there a additive that might clean the fuel system? I use stabil in most of my gas but i ride the atv very infrequent, was sick in Feb and did not get to go out on ice with it, so gas may well be pretty old. I thought I saw an add for smething amsoil sells that makes engines run cleaner,,, If not I will have to take it to a shop...

Thanks

[DirtDemon]

Drain the tank completely, make sure the petcock is clear, replace any fuel filters or screens in the fuel line. Last thing, take the carb COMPLETELY apart and clean everything. Use compressed air for any passages that you cannot clean manually. Make sure to blow through the jets with carb cleaner and compressed air, be careful not to blow them out of your hand, they can be hard to find.

[ZZ71]

I thought I saw an add for smething amsoil sells that makes engines run cleaner

This is probably what you are looking for AMSOIL Quickshot SE

I gave a bottle of this to my neighbor who's riding lawn mower seemed on its last legs. After mowing for about 30 min the engine started running better and now he has no excuse buy a new one.

Note-Moisture/water in the fuel can cause it to backfire.

If the fuel you use has any Ethanol in it, you should never keep that fuel more than 90 days and less in humid climates. A friend is a boat dealer and they are seeing a lot of engine problems they say is because of the E10 Ethanol and infrequent use. Boaters are breaking down out on the lake and having to spend a lot of $$ to have the fuel system cleaned out just when the want to you their boats.

Question:

How can ethanol be harmful if it is formulated into most pump fuel available in the U.S.?

Answer:

Ethanol can cause significant problems in many different applications due to the differences in properties compared to gasoline:

a. Ethanol is hygroscopic, which means it has a tendency to absorb water.

b. When ethanol absorbs water, it readily separates from gasoline and, because it is heavier, falls to the bottom of the tank.

c. The ethanol/water mixture in the bottom of the tank degrades relatively quickly.

d. Ethanol contains less energy per gallon compared to gasoline. Based on this, many new vehicles have computer systems that sense and correct for high ethanol content. Small engines and most power sports equipment are not programmed to detect this and a lean burn situation results.

e. When the ethanol rich mixture is pulled into the engine this lean burn increases combustion temperatures significantly, which can lead to severe engine damage.

f. When a mixture of water and ethanol degrades and creates gums, varnish and other insoluble debris, fuel flow passages can become narrow or plug, significantly affecting engine performance.

g. When the correct amount of fuel cannot flow to the engine, equipment becomes difficult to start and performance becomes unstable.

Edited July 16, 2010 by ZZ71

[wylde1]

that is a lot of good info. I had asked someone a while ago if the ethanol had any effects on 2 strokes since it had to mix with oil and the guy told me it wouldnt hurt anything.

[luckyhook]

thanks i will see if i can find some and give it a try.

[tdayco]

I also have the same issue with my 99 sportsman 500. I have taken the carb apart and found nothing wrong. Could it be some sort of safety mode? I'm stumped because it ran perfect the day before. When your talking louder, I noticed that the noise is coming from the air box not the exchaust. Seems to be blowing fuel/air back into the airbox.

[luckyhook]

I had a mechanic friend of mine look at it and he thought would be carb but carb was ok, he went a little further and discovered the camshaft is rounded over so valves are not opening correctly.

Now I have to figure if it is worth the up to $1000 to have this fixed as it is way past my ability. He said he talked to some Polaris repair people and they told him it was a common thing with this model year sportsman. Hope yours is something much simpler, mine seemed to start the same way as yours did and got worse fairly quickly.

Good luck

[tdayco]

I was hoping you wernt going to say that. I did suspect it. How was the mech. able to find it?

[tdayco]

I did notice that it was consuming alot of fuel on the last tank. Did yours do the same? Im going to check to see if there is fuel in the oil.

[luckyhook]

I didnt run long enough too know if i used moore fuel. the friend thought sure would be main jet but he took carb boot off and jets were ok, then he called a friend of his at polaris and they told him to check the camshaft, he took something off to try and adjust the valves but that is when he could see crank cam was rounded out. I wasnt there when he worked on it for me. He told me the crank was about 450 and valves and rockers probably should be replaced if going that far, he said looking at 5 to 6 hours labor to do the job and would run around 1000...mine started as noise and power loss then as i tried things just kept getting worse before it finally just kept backfiring when giving it gas.

[tdayco]

thanks for the info. I'm pretty certain that I am in the same boat. Guess I'll part it out. Its had a tough life. Good luck with yours. Watch ebay a craigs list for a used motor. I had good luck on ebay in the past.

[DirtDemon]

I also have the same issue with my 99 sportsman 500. I have taken the carb apart and found nothing wrong. Could it be some sort of safety mode? I'm stumped because it ran perfect the day before. When your talking louder, I noticed that the noise is coming from the air box not the exchaust. Seems to be blowing fuel/air back into the airbox.

Blowing air/fuel back into the airbox is not a problem with the cam, but valve adjustment. They intake valves aren't closing all the way, that is why you are getting the blowback. That is not to say that your cam isn't getting worn, but I would be cautious of what you are told by a dealer tech. They will quote you for everything that could possibly be wrong and more to make sure they get your problem covered, and they still miss stuff. Also, if either of you guys do elect to have a dealer fix your machine, don't buy the parts from them, you can save 30% or more by purchasing OEM parts from an online retailer. Servce Honda and Babbits online have very good prices on OEM parts. They are the exact same parts your dealer gets just without their markup.

he took something off to try and adjust the valves but that is when he could see crank cam was rounded out. I wasnt there when he worked on it for me. He told me the crank was about 450

Did he adjust the valves, or just determine that the cam was rounded? I don't know if it is your friend, or your translation of what he said to you, but there is no such thing as a crank cam, and the cam for that rig runs a tad over $200, the crank, which has no direct influence on the function of your valves, runs about $560. Do you trust that your friend really knows what he is doing? Just a question, not a knock on his abilities.

Again, a dealer is going to rape you when it comes to parts, and in most cases, labor costs too. I am shure that there are plenty of reputable machine shops around that will do the work for a much better rate, possibly better quality, and offer cheaper prices on the same OEM or aftermarket parts.

Neither of you guys are too far from PA, I would give these guys a call and see what they can do for you, they have some great prices on machine work and quality aftermarket parts for other machines, it wouln't hurt to give them a call and compare thier prices with some other places as well as a dealer. I am sure the dealer will not be the cheapest by a longshot.

http://advmachining.com/Services.html

Edited August 9, 2010 by DirtDemon

[luckyhook]

reply it was the cam shaft, my mistake, . I tried to delete the crank part and insert cam but i guess i missed, He worked for Polaris a long time ago and is just a backyard mechanic now who has worked on a few things for me at a reasonable rate and i trust what he says.

He told me prices roughly would be 245camshaft, rockerarm intake 122, rockerarm exhaust67 and gasket 15.

Her said if your going to go as far as replacing the camshaft it is probably worth it to change the rocker arms as well.

I am still undecided which route to take. I will look at the sites that you suggested to see what prices are quoted there for the parts.

Oh he did adjust the valves which made it better but still not right, no power and some backfiring.

[tdayco]

I adjusted valves and it still sounds like its in some sort of limp mode. Cam appeared to be working correctly. It got hot on me one time and went into limp mode. This feels the same way. Is there anything that I could unplug to bypass that? Again it starts and idles prefect. spark plug is golden brown. Plug cap had some black in it though.

Edited August 9, 2010 by tdayco

[tdayco]

O.K. I think my problem is in the overide curcuit. Symptoms act the same as the overide used to act. How can I disable that curcuit?

[bowzer]

what did you find to resolve this issue. contact me at [email protected] thanks

[Tinkerman]

500 are bad about warin out the exhaust lobe on the cam..... It will idle and run up to 20 25 mph then bogs out and backfires....new cam needed! pull the valve cover and spark plug kick the motor over the rockers should raise the same height if the front is less than the back its the exhaust cam. it will be obvious. good luck Todd Polarisatvrepair.com

[bowzer]

you guys hit the nail on the head!!! thanks so much replaced cam and all the rocker arms. I did notice they have two oil holes on the exhaust lobe now on the cam. must have been a not enough oil issue redesign

[tdayco]

what did you find to resolve this issue. contact me at [email protected] thanks

Bad cam lobe. Sold for parts and bought an arctic cat.