No power


  #1  
Old 02-04-09, 05:59 AM
R
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No power

I have a 1999 Polaris Sportsman 500 ,Last summer I went on an ATV run of about a hundred miles, Towards the end of the ride I noticed the motor was starting to knock and it did not seem to have much power,especially upon acceleration. When I got the machine home I had the cam replaced which cured the knocking but when I test drove it at the shop the power still was not right...actually not any better than before the repair. I told the mechanic about it and he messed around with it for a few minutes and determined that the air box was not sealed properly and put a new gasket in. The problem seemed to be solved but since I got it home the problem has resurfaced. I tested the compression ,It's fine and,replaced the plug and fuel filter to no avail..The problem is not constant ,sometimes it runs great. What do you think is the problem ?????.


Thanks,

Randy
 
  #2  
Old 02-05-09, 05:48 AM
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The on then off problems are really tough to diagnose even if the machine is right in front of you.

Is the problem associated with a particular throttle opening or are there specific circumstances it surfaces - for instance under load or at a certain rpm level? Is the engine idling properly and accelerating well?

I'm not sure an airbox gasket would be guilty of a performance problem on a carburetor fed engine, although the airfilter can affect the fuel air mix. It really depends how much of a loss we're talking about.

Certainly if you had a cam with flat lobes replaced, you should be able to tell the difference in the before and after performance of the engine. That alone will kill engine power.

My first guess, in light of the erratic nature of the problem would have to be the carburetor. A kit may cure everything.

My second guess would be the CDI or possibly the coil on its way out. If you had a spurt of the low power and you checked the plugs during it you may have blackened plugs. If so that would indicate poor ignition and possibly a bad coil.
 

Last edited by marbobj; 02-05-09 at 07:43 AM.
  #3  
Old 02-15-09, 05:48 PM
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I just put the carb back together after a good teardown cleaning and it runs like a new machine!!!
 
 

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