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Discussion Starter #1
Hey folks,

I just got a piece-o-crap 2000 Polaris 325 Trail Boss atv for pretty cheap because the engine makes a real bad clanking/knocking noise. The guy I got it from said that it "needs a new connecting rod". Does that make sense or is it more likely valves out of adjustment or the like? It's a 4 stroke engine. I've attached a pic and horrible sounding vid of the beastola.

http://www.youtube.com/watch?v=_cK0Gjnx45M

 

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First off, Welcome to the board!
 

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Take the valve cover off, rotate the engine to top dead center(tdc) on the compression stoke(this is when the piston reaches top after the intake valves close), now check for play between the valves and rocker arms, if there is only a tiny amount of play(2 thicknesses of paper is only a very rough guide line!Use feeler gauges if you have them) your problem lies with the connecting rod, if there is lots of play get the proper specs out of the shop manual and complete a valve lash adjustment. An easy but not very accurate way to find tdc is to use a long 1/4 inch extension in the spark plug hole, make sure you guide the extension so as not to do any damage! Stop turning the crank when the piston reaches the top. In your video it sounds like valves to me, but that only a recording. Am sorry that I don't have the valve lash specs.


Regards
James
 

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i just played your video for me and 3 other master techs in are service dept. that is not valves. that is internal bearing or rod noise. time for a rebuild.
 

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Discussion Starter #6
Hey guys thanks for all the advice, good news and bad. I'm going to tear into it tomorrow...and take some pics...and try to get to the bottom of it.

Any good parts sources for this model ATV? I've found bikebandit but was wondering if anything else was out there/better?

Anyone mind telling me a list of parts I need to buy to complete a rebuild? Or at least tell me what I'm missing?

-Overbore piston
-Rings
-more than likely a connecting rod
-main bearings
-full gasket set
-other stuff I'm forgetting...

Thanks fellas
 

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Discussion Starter #7
Alright, pulled the top end off today after checking the valve clearence (it was right on) and it was definately the rod. I drained the oil and there was about a 1/2 a qt of black gunk; pretty much explains the situation. The camshaft and camshaft journals in the head are shot so the head/cam/valve cover will need replaced. Probably will need a new crankshaft....overall a very expensive prospective rebuild at ~$700.00.

Does anyone know if other models/sizes of engines will fit into the engine bay of the 325 Trail Boss?
 

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may want to check out a used motor. can check with eastcoastatv.com 610-282-0369 for used atv parts.
 

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i have not used them matt but have read there are good to deal with.
 

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You want to double check the drive clutch if it is worn it will make a knocking sound like a bad crank.
Just start it up once you pull the clutch off..
Good luck, Todd
 
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