polaris sportsman 500 timing

04sportsman · #1 (**permalink**) 01-21-2012, 06:44 AM

The last 2 times I have tried to start it, it will turn for a split second, then lock up. I try pulling the pull cord and nothing. Eventually ther eletric start will turn it, then after that, it turns over fine and starts right up. Motor runs good and no abnormal noises coming from it. I seem to think it maybe the compression release, cause it locks, will turn slow, then seems once the piston is on the decompression stoke, its turns freely. Anyone got any ideas? Is this a common problem?

Kevcules · #2 (**permalink**) 01-21-2012, 07:45 AM

They do have a lot of compression and that's why it's hard to turn over. If the electric start doesn't turn it over ,then your battery isn't charged well enough or you need a new one. Maybe your starter is going bad also.I have a 2001 and haven't had to use my pull start much but when I do, if you catch it at a certain spot , it does pull hard. Once by that spot , it's easier... Fairly common I think...

Kevin

04sportsman · #3 (**permalink**) 01-24-2012, 03:27 PM

I had my battery on charge for a few days. Went to start it today after sitting for a few days, and again, turned for a split second, then locked up. Pull cord would not budge. After turning the key a few times it finally broke loose and turned over and started fine. I got to think its a compression release issue? Can you work on the compression release without tearing the motor apart?

4getful2 · #4 (**permalink**) 01-25-2012, 01:20 AM

Try using jumper cables with a known good battery. if that doesn't help ,then yes you can work on it without taking the motor apart. Just remove the valve cover and you're there. hopefully there is room to work on it.
There's not much to the decompressoe, a spring and a lil ball, so it may be time for a cam, try adjusting the valves first --set all at .006" at top dead center. inspect cam lobes too.

04sportsman · #5 (**permalink**) 01-25-2012, 01:45 PM

So I tried something different today. I tried pull starting it first rather than using the electric start. It pulled 3 times fine with no lock up. I then hit the electric start and it fired up fine. Maybe it is just something in the starter drive, but we will see if I'm that lucky.

Russ C · #6 (**permalink**) 01-25-2012, 04:01 PM

maybe bad brushes in starter, try hiitin the starter with a bar or hammer next time it does it, if it starts, starter going bad

sportsman 500 H.O · #7 (**permalink**) 01-28-2012, 03:56 PM

I too have the same problem with my 2009 500, i had the starter rebuilt, new battery, checked all the grounds and ignition wires and have just replaced the spring in the compression lock, went to start it and it still locks up. The engine runs fine and even with this problem the engine always starts but it really bothers me and Polaris isn't doing anything to help me.

Russ C · #8 (**permalink**) 01-28-2012, 04:35 PM

I have one with 11to one compression and it does it occasionally, let go of starter button and try again and it fires up, have learned to live with it, if it comes up on compression just right, starter wont turn it

john luttrell · #9 (**permalink**) 01-29-2012, 02:45 PM

Quote:

Originally Posted by sportsman 500 H.O

I too have the same problem with my 2009 500, i had the starter rebuilt, new battery, checked all the grounds and ignition wires and have just replaced the spring in the compression lock, went to start it and it still locks up. The engine runs fine and even with this problem the engine always starts but it really bothers me and Polaris isn't doing anything to help me.

Hello, it looks like you have covered most of what could cause the slow cranking, but have you checked the valve clearance? If the valve clearance is too loose, the check ball that the compression release cam holds in place, to momentarily release the compression will not contact the rocker arm for the exhaust valve; it has to make contact in order to bump the exhaust valve off it's seat momentarily in order to release the compression. If the valve adjustment is correct and it still does not release the compression, there is a chance that the check ball has fallen out, I have heard of this happening, but have never seen it myself. The check ball is on the back side of the center cam lobe and you should be able to see it with the valve cover off; you may need a small mirror to get a visual, but you should be able to see if it's missing.

The bad thing is, that you can not, to my knowledge buy a new check ball and keeper, which means you would need to buy a new cam shaft to get it. That would be a question to ask a good parts man though. As far as adding an extra wrap on the release spring, I'd advise against it, as the spring needs to be light enough to allow the release check ball to completely disengage the rocker arm when centrifugal force over comes the spring at around 300 rpm, or you could possibly burn a valve. The valve clearance on both the intake and exhaust valves is .006" and here is the page from the manual on how to adjust them, in case you don't have the manual for it. Hope this helps, don't hesitate to get back with me, I'm sure we can get it figured out. I also attached a good pic of how the spring should be installed, it will not operate correctly if installed wrong.

sportsman 500 H.O · #10 (**permalink**) 01-30-2012, 01:30 PM

I did a valve adjustment in the spring and the valves were at .006. The other day when i was replacing the spring in the compression lock, i had the valve cover off and did check to see if the ball in the cam was still there and could see that it was. I spun the clutch and did see that the ball was opening and closing the exhaust valve properly. I just keep thinking that the spring i ordered doesn't have enough tension to operate the decompression lever. The engine does not do it all the time, it starts fine some times and starts slow other times.