Crank re-balancing ???

Old 07-08-2009, 05:51 PM
  #1  
jackbn
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Default Crank re-balancing ???

I've got a rotating assembly that has been balanced. Found out that I need to go over .030 more (total .060 over). Now my question is I need to go to a different piston and rod. The weight of the "old" piston and rod is 1660 grams. The weight of the new piston and rod is 1650 grams. How far off on the weight can you go without re-balancing the crank ?
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Old 07-08-2009, 07:29 PM
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bowhay
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u may be ablle to get away with that, but i would deffinately not risk it,
i am also rebalancing a crank, i got new rods and pistons, the pistons are lighter than the old ones and the rods a lil heavier, i dont remember the actual amount of grams but it is very close
and i am still having it re ballanced to be safe
i mean u can think of it this way, 200 dollars to get it balanced give or take, more if they have to add metal.
or u can figure the cose of replacing the hole rotating assembly and possibly block if somethin goes wrong
jmo
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Old 07-08-2009, 07:43 PM
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PAR
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You will be safe with 10 grams. Going lighter is always better. You can go up to 25 or 30 lighter, but not heavier. Remember, just cause the weight is 10 grams, that doesn't mean it is 10 grams out of balance. It may only be 3 or 4 grams out with that 10 grams.
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Old 07-09-2009, 06:36 AM
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oldandtired
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Originally Posted by PAR
You will be safe with 10 grams. Going lighter is always better. You can go up to 25 or 30 lighter, but not heavier. Remember, just cause the weight is 10 grams, that doesn't mean it is 10 grams out of balance. It may only be 3 or 4 grams out with that 10 grams.
Par is correct. You take 100% of the rod end and 50% of the piston end in the calculation for balance.

Dave
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