I have searched the forum, and have not found 1 person who mention's the loud noise comming from the cam after the engine warms up. I took mine (sportsman) back to the dealer when it only had fifteem minutes on it. He said they all sounded that way, and started one to prove it.
It's not normal folks..
It took three trips to the dealer, and me dissasembling my own moter to prove it was a problem that needs to be addressed. The cam is suffering damage, the exaust rocker arm follower is suffering damage, and the end play thrust plate is being beat up. All three were damaged to the point that their own service manual wsaid that they need replacing.
The point I'm makeing here, is that if you have a noticable noise that starts getting louder after it warms up a few minutes, go to your dealer and complain.
I was stone walled by the dealer because it's a manufacturing defect in the engine that they buy from FUJI and they have no way to repair it (free to them). I called Polaris diret and they refused to talk with me about it and kept referring me to their dealer list.

I don't need mine fixed, figured it out myself. I even tried to give Polaris the solution and they would not accept it from me, still not admiting they have a problem.

I would like to hear from the 500 HO users here if they have the problem.

It's not a problem with the older 500s or the 400s because they have a different cam, which is part of the reason Polaris says they have had 400s (same basic engine) in the field for yars with no come backs.

Les Stotler
Newcastle OK

 

I have one but so far no unusal noise yet, I only have ten hours on it.

 

Mine is a 2002, dont know if that makes a differance.[img]i/expressions/face-icon-small-blush.gif[/img]

 

What kind of damage are the parts suffering from???


And your solution was???

FWIW
The 500HO engine is known to be a little noisy....

 

Don't you hate that ... you can see the problem .... see a solution ... and
they won't listen to you !!!

The best you can do is pass along the solution to others that they may not
have to endoure what you have [img]i/expressions/face-icon-small-sad.gif[/img]

 

My 01 Has over 3,000 miles and 300 or 400 hours on it and it still sounds the same as day one.

 

The automatic decompression device is not working as planned. It is desiged so that when at rest, a little weighed arm on the left end of the cam is held back by a spring, thus turning out a flat on the end of it to force a steel ball out inro the edge of the cam. Said ball is on the oppisite side frome the exaust lobe and is set to hold the exaust valve open a minimal amount on the compression stroke. (this allows for a smaller starter/battery combination, plus helps aleviate hard rope pulling). When the engine cranks up, centrifical force causes the weight to swing out toward the outside, thus turning the shaft out so the flat allows the ball to return back into the cam. Herein lies the problem. The HO has a wider lift cam (thus the HO part) and a design flaw in the system becomes apparant. It works fine untill the oil pressure fills the cavity where this weight resides (inside the cap on the left side of the engine under the radiator return hose. This cap is the thrust plate for end play on the cam, plus the removal hole for the cam). This is where it gets complicated. This cavity fills with oil, as the oil pressureization for the cam comes into it to get into the center of the cam. The cam is spinning around in the liquid, the open side of the weight is spinning into the oil, you would think that the force of this liquid would hold it open, but it is also spinning at a somwhat slower rate. This is not the problem, the problem is that liquid, and air, moves much slower at the surface of the outside edge, and some right on the surface hardly moves at all. The space between the swinging weight and the outside edge of the cavity is very small. The shape of the weight is somewhat like the cross section of an airplane wing, but with an exaggerated hump on the front of it. As it swings around, it acts like an oil pump, compressing the oil smaller and smaller against the surface of the outside edge. Only oil does not compress, and there is no outlet for the pressure built up, so it forces the weight back, turning the flat a little. I think this process continues untill a happy medium is reached with the spring and the oil trying to force the weight into the center and centrifugal force trying to force it out. Unfortunately the rise time on this cam comes too soon. The ball strikes the cam follower ,on one side which rocks it a little, which also pushes the cam to the side a little. which sets up an oscillation that causes the cam to strike the thrust plate, BAM.

As to the damage. Forged metal is kinda hardened in little thin layers. My cam follower is worn throught two laweres, witha groove 3/8 inches long. It is deep enough to feel as well as see. The area around where the ball protrudes from the cam is scored for about a qtr inch some what deeper. The thrust plate had a circle of hardened alluminum that came off like a washer. it was about ten thousands thick. There is no way I can measure the wear to the ball.

The cure. At first, I put grooves along the weight, like you would see on a centrifugal clutch(thats why they are there by the way) to allow the oil an escape path. This worked about 60 percent, that is the noise was reduced that much, which meant it was not the whole cure. Next, I removed the cap and cut the taper off the inside surface so that it is flat, giving a little more space between the flying weight and the wall. That took care of 99 percent of the noise. My next test will be to groove the inside of the cap, put in an ungrooved weight and see how it goes.


What is the cost of leaving it alone? Who knows. The little ball is harder than you know what, but it will eventually wear thin enough to fly out, going who knows where to do who knows what. Replacing the ball? not to be done, you have to buy a new cam $$$$$$ Starting it without the ball, not likely says the Polaris Mechanic. The little weighted arm is sixty bucks. Will the wear on the rocker arm or cam eventually lead to cracks and failure? Some day, with enough heating, pressure, and cooling cycles, but who knows when.



"I have one but so far no unusal noise yet, I only have ten hours on it." My suggestion is to listen to it when it starts, its pretty quiet, then notice it ten minutes later. It should be at its quietest after oil pressure comes up and noiser when first started.

"My 01 Has over 3,000 miles and 300 or 400 hours on it and it still sounds the same as day one. " True, the problem is built in, not a product of wear. Try the above test.

"FWIW
The 500HO engine is known to be a little noisy.... " Thats the same thing my dealer told me, when I asked him why, he didn't seem to care, the HO's were all that way was good enough for him.

If You want to fix it, there is the cure, If not, OK. But it embarassed me to be around other riders with a machine that sounds like a thrashing machine.

Les Stotler
Newcastle OK (forgive my typing, my indexx finger is in a splint

 

The cam in the H O is junk. Polaris knows it, but says they have never had a problem. We have replaced several with bad exhaust lobes. The new cams are suppose to be a upgrade. Replace the cam and exhaust rocker. Good Luck!!!!!!