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Discussion Starter #1
I have a 1980 arctic cat jag 3000 f/a 900 original miles that just developed an engine knock. You notice the knock at idle and when the engine comes up to speed. It doesnt knock when you rev up or when its coming down. The knock isnt very loud but its enough that i noticed it and have ruled out all the stupid obvious problems (loose belt protector, bolts, etc) from what i have read it sounds like its my piston rod bearings? I dont know if anyone else has dealt with this and can shed some light. I would much rather do a top end rebuild that have to tear the whole thing down. I also run my cat rich, usualy 65:1. Thank you all in advace for your advice / thoughts!!
 

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65:1 would be too lean. try 40:1, that would be richer....20:1 would be even more rich. 65:1 wont provide enough oil. You have a spark knock, thats if you havent wrecked the bearings. What do the plugs look like?
 

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i had a 79 when i was a kid; i miss that sled; if i remember it should be 50:1 it was on the tag just above the gas cap.
the "hex"clutch clunks on those too
 

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Discussion Starter #5
I replaced the plugs at the beginning of the season when i pulled them out yesterday they looked a little ashen but nothing to write home about. Also i had my ratio off, the machine calls for 50:1 i run mine about 35-40:1. Can you explain what a spark plug knock is? And how would i go about fixing that? I just had the heads off a few weeks ago and replaced the head gaskets bc they were leaking. It was only a few hours on the machine later that i noticed the knock. do you think i could get away with just replacing the top end? I just refuse to believe that with 900 miles on the machine that the rods and anything of the driveshaft is worn out that it just insane.
 
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