what are the symptoms of bad conn. rod bearings - Snowmobile Forum: Your #1 Snowmobile Forum
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post #1 of 9 (permalink) Old 11-20-2012, 06:21 PM Thread Starter
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what are the symptoms of bad conn. rod bearings

well, i guess i could type it again, but the title says it all... also how would one diagnose?
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post #2 of 9 (permalink) Old 11-20-2012, 09:01 PM
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You will probably have a engine knock if your rod bearings are bad. What you could do is pull the spark plugs out and on the cylinder you are checking rotate the engine until that piston is on the down stroke stick a screwdriver down the spark plug hole and gently push down on the piston and if you feel it give a little then that could mean you have bad rod bearings. If they are good and you have an engine knock then it could possibly be piston slap or you have bad crank bearings.
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post #3 of 9 (permalink) Old 11-21-2012, 07:50 AM Thread Starter
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this enging sat for about 3 years and i know the p/o did not fog it. are the wrist pins more prone to failure or are the lower con rod bearings? no knock, slight quiet rattle at idle, starts right up, idles perfect. (2000 polaris xc500 w/ 1900 miles)
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post #4 of 9 (permalink) Old 11-21-2012, 09:46 AM
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In that case if u are worried about the lack of lubrication from sitting you could hold the oil pump in the wide open position the next time u start it just to give it a little more oil or possible run a little premix in the fuel tank. Just make sure u have all the old fuel out of the system. Since there are no real signs of engine issues I would do one of these and hope for the best.

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post #5 of 9 (permalink) Old 11-21-2012, 10:37 AM
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Or pistons clearance may be out of spec?? WL
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post #6 of 9 (permalink) Old 11-21-2012, 12:48 PM Thread Starter
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Or pistons clearance may be out of spec?? WL
when i pulled the exhaust man. i noticed that i was able to rock the pistons in the jugs slightly on the wrist pin. is this the clearance youre refering to?
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post #7 of 9 (permalink) Old 11-21-2012, 03:08 PM
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Yup - WL
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post #8 of 9 (permalink) Old 11-21-2012, 06:44 PM Thread Starter
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Or pistons clearance may be out of spec?? WL
so i should not be able to feel them rocking in the cyls at all? only 1955 miles and its time for a top end so soon. man i got this thing because it was said to be in the bullet proof catagory.

i tried the "push down on the piston through spark plug hole" and on the down stroke, i did notice slight play. not sure if its the conn rod bearings or the piston rocking.

not hearing any piston slap or any knocking at all. im i just getting nurotic from too much forum time?
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post #9 of 9 (permalink) Old 11-21-2012, 08:45 PM
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The "rocking" you are seeing is normal- pistons are much smaller in diameter at the top than they are at the bottom when cold. You are worrying too much.

They all start turning to junk as soon as you pull the rope...
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