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2000 Artic Cat 300 4x4 engine issues

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Greetings all.   Newbe to ATV's [but not to general wrenching on Detroit Iron and Asian bikes].


Friend is 2nd owner of said A.C.   Has had it about 4 years and said when he got it, PO had ridden it hard and put it away wet many times over.   Current owner has done massive repairs to the ATV, but only carb work to the powerplant.


Last week, it quit running altogether.   Cranks healthy and just because he had never done it, we put in a new NGK plug.   Spark is fat and blue, but still no start.   Shot starter fluid down her throat while cranking with no results.   She didn't even pop.  


He seems to remember, back in the day, when he tried to pull the engine through with the pull start, he couldn't do it without opening the compression release.   Currently, the compression release does not make a difference, so, dry compression = 60, wet = 75.  We pulled the head to ship off to machine shop.   During the initial inspection, found sever wear marks from the cam chain in the cam sprocket pocket area.   He seems to think the chain has stretched [he's a good wrench if it has a hood, but no experience on motorcycle engines, so he's drawing on old school experience with V8 fiber cam timing gears and the such).   I'm leaning more towards the cam chain tensioner (sp?) being inop, as I have never heard of any issues with the cam chains actually stretching beyond the limits of an operation tensioner.   I understand that because the crank gear is pulling the chain from the bottom, the bottom run of the chain is generally straight and under tension, and the tension adjuster takes up the slack from the top run of the chain.


Question #1; Is the tensioner manually set and left as is, or does engine oil pressure maintain the tension (oil level is full and no other 'unusual' metallic sounds from the engine when it was running).


I would really appreciate any and all advise and suggestions on:


(a) past knowledge and experience with the wear marks we found,

(B) past knowledge and experience on the cam chain tensioner,

© link to a downloadable engine service manual, specifically info about the tensioner,

(d) link to a downloadable exploded diagras of the engine / trans / rear diff, and

(e) instructions and guidance from those much more familiar as to setting the cam chain timing during reassembly and also top end torque values.


Thanks much

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