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Discussion Starter #1
Hey Guys, new to this site. Nice to have finally found somewhere to look for help.
My Magnum has issues with hard starting, backfires, overheats, etc. I'm at a loss. I've gone through the carb etc. I heard that these have issues with the cams. How can I check to see if the cam is shot without pulling out the engine. Or what else should I look for. Just starting to get looking at it since its time to put the sled away.
Thanks

Jeff
 

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welcome....

my first thought was carb, but if that is all set and clean, then the hard starting my be a result of valves out of adjustment. any idea when the last valve job was at?
 

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You can inspect the cam by pulling the top valve cover off the top of the motor. Usually the exhaust lobe will wear down very badly on these models and give the troubles you are describing. Most the time if it is the cam it will only idle and will not pull any rpm. Did you check the spark plug? What other info can you give? What does it do when it overheats? When does it backfire, etc?
 

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welcome to the site!........you've come to the right place!
 

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Discussion Starter #6
I've never set the valves so I'm not sure. Picked it up a couple years ago for the kids. My 93 TrailBoss 350L is a 2 stroke with no issues, but 4 strokes are new to me in quads. Once it does start it will rev, but its boggy, no power. Plug looks fine, but I havent got into it this year yet. I can see where a valve set would help. Can I pull the valve cover off without pulling the motor? If so, what do I set the valves at? Are they solid lifters with a lash setting or are they hydraulic set at 0 lash?
Thanks Guys
Jeff
 

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Discussion Starter #7
If it is the cam, what are my options? Also when the cam gets replaced, should the lifters etc be done as well or do they last and just wear out the cam?
Thanks
 

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Discussion Starter #9
Are there any other engines where the cam is interchangable? And do they have the same problems? Whats the cause, oil or???
Thanks
 

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Any polaris 425, 500, 500ho will interchange. From what i have read the older cams had a hardness issue and the exhaust lobe would wear down very fast. Oil I'm sure is a big issue too. Off the shelf oils nowadays do not have the zinc and phosphorous additives due to new emissions regulations. Racing, or specific atv motorcycle oils should be ok. I run an additive with zinc in mine. Any cam you buy now for the 425 or 500 is the newer 500ho cam. I believe that the older part numbers has been superseded to the HO. Buy a HO cam though just be be sure if you have to.
 

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Double check the slide diaphragm in the carb the slightest hole or tear will cause bogging and slow revs. I had this happen to mine during a rebuild.
 

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Discussion Starter #13
Thanks. I'm going to start into it this weekend. Probably will end up going further than I anticipate.
What about tires. Its going to need this year, what does everyone like. I dont really have trails. Its field, bush, mud
 

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I like the ground clearance, it handles quite well for a larger machine,the awd button makes switching from 2wd to 4wd a breeze, all in all its one great machine..
 

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Discussion Starter #15
Well guys, turns out it was a coil on the stator. Dealer finally tracked it down. They were at a loss as well.
Thanks for all your help
Jeff
 
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