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xracer390

2004.5 400 Sportsman

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Father in law dropped it off to see if I could fix. Says last time it ran it had a grinding/gear type of noise when it started but he rode it anyway. Acted like the belt slipping that day and died out in the woods.

     Its at my house now and there is has little to no oil in it, leaking fairly bad someplace, and gas in the airbox but it seems to turn over OK (wont fire)  Did it jump time?

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I'd suggest inspecting the cam itself. The 500 Polaris engines often had faulty camshafts that rounded off. Possibly the 400 had similar issues.

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2 hours ago, doug the slug said:

I'd suggest inspecting the cam itself. The 500 Polaris engines often had faulty camshafts that rounded off. Possibly the 400 had similar issues.

Wouldnt it still have good compression? Just poor valve lift?

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I'm sure that they're related, depends on how worn the cam is. Even with a decompresser, 30psi sounds pretty low.

Have you been able to check cam timing?

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On 10/7/2020 at 3:33 PM, doug the slug said:

I'm sure that they're related, depends on how worn the cam is. Even with a decompresser, 30psi sounds pretty low.

Have you been able to check cam timing?

Motor coming out. He found a used motor. Hope its good.

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So, does anybody know. This quad is a 2004.5. Motor is late 90s we were told. Few difference I think I have taken care of. One is a fitting on the back of the head that the 2004.5 does not have. Anybody know what it was for?

20201016_182344.jpg

20201016_182433.jpg

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