Engine builders question

A 650 engine is being converted to a 750. By boring the case and installing the 750 jugs with pistons. My question is- What about the balance of the engine? Do you have to rebalance the engine? Since these turn 9000+ rpm. Also if installing the 810 kit that will throught it off more. What do you think about balancing? Does it need to be done?

falicon or some place like that could probably do it,i think it would be pretty pricey though.ive never had a motorcycle crank and pistons balanced i allways do car engines when i build them though.

I have never heard of anyone balancing the crank when installing 750 pistons on a 650, or installing an 810 kit, and I have never heard anyone complain about additional vibration, so I'd say it's probably not needed.

I think you are looking at it the wrong way.
If the crank is balanced from the factory (rotating mass)
Then it does not matter what the pistons weight as long as they all weight the same.
2 going up while 2 go down (on a 4 cyl.)
It balances itself.

Inline four cylinder cranks are "self canceling" It doesn't matter how much the bolt on components weigh, as long as they all weigh exactly the same. So you do not need to rebalance your crank for what you are doing.

See our crank site
www.racecranks.com

Jay













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I have taken v8's to get balanced before and they allways ask for the pistons, rings, connecting rods, crank, etc.
What your telling me is that the inline fours are self balancing and dont require a balance. If everythiing weights the same I will be fine:unsure: