zmotorsports
ALLIANCE MEMBER
I have attached a few pics of a camshaft that I just removed from a clients Polaris Sportsman 500 ATV. He brought it to me complaining that it didn't have any power and two other shops had already worked on it, one found nothing wrong with it and the other replaced most of the ignition system because it was backfiring and they said it was due to bad ignition. After spending over $500.00 dollars on ignition parts they still could not get it to run and said they couldn't afford to spend any more time on it. He was referred to me after complaining at the local NAPA store.
What kills me is he asks me to keep the price down due to the fact that he already spent $500.00 on it and didn't fix the problem. I love it when I am asked to work for nothing because some crook took advantage of someone and made off with their money. Anyway that is whole other subject.
Upon troubleshooting I noticed it would fire and idle beautifully, however, upon applying very little throttle it would sputter and backfire as per the owners complaint. I removed the airbox and noticed it was backfiring through the intake not the exhaust. Generally when backfiring through the intake it is not ignition related so this was suspicious why the first shop changed all of the ignition components. I did a compression test and cylinder leakage test and saw nothing out of the ordinary other than maybe a little low on compression. I thought to myselft I wonder if the exhaust rocker is damaged or something with the camshaft not letting the exhaust escape the engine. I removed the body, fuel tank and rocker cover and bingo, camshaft is trashed. I have attached a couple pictures of the camshaft. The first pic is of the camshaft and exhaust rocker, the second pic is of the camshaft looking at an angle towards the exhaust lobe which is pretty much missing and the third pic is of the exhaust rocker which is damaged as well. After a little research I discovered that early Polaris 500 engines were notorious for this due to the extra wide camshaft lobe and poor oiling capabilities. It looks like a new camshaft is available which will fix the problem. Polaris evidently replaced quite a few under warranty, but the warranty is long gone on this quad. Thanks for looking, Mike.
What kills me is he asks me to keep the price down due to the fact that he already spent $500.00 on it and didn't fix the problem. I love it when I am asked to work for nothing because some crook took advantage of someone and made off with their money. Anyway that is whole other subject.
Upon troubleshooting I noticed it would fire and idle beautifully, however, upon applying very little throttle it would sputter and backfire as per the owners complaint. I removed the airbox and noticed it was backfiring through the intake not the exhaust. Generally when backfiring through the intake it is not ignition related so this was suspicious why the first shop changed all of the ignition components. I did a compression test and cylinder leakage test and saw nothing out of the ordinary other than maybe a little low on compression. I thought to myselft I wonder if the exhaust rocker is damaged or something with the camshaft not letting the exhaust escape the engine. I removed the body, fuel tank and rocker cover and bingo, camshaft is trashed. I have attached a couple pictures of the camshaft. The first pic is of the camshaft and exhaust rocker, the second pic is of the camshaft looking at an angle towards the exhaust lobe which is pretty much missing and the third pic is of the exhaust rocker which is damaged as well. After a little research I discovered that early Polaris 500 engines were notorious for this due to the extra wide camshaft lobe and poor oiling capabilities. It looks like a new camshaft is available which will fix the problem. Polaris evidently replaced quite a few under warranty, but the warranty is long gone on this quad. Thanks for looking, Mike.
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Lack of funds and time usualy keeps me from going more. I ride a 07 Honda TRX450.
