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Workshop => Engine and Bottom End => Topic started by: JesseA420 on April 10, 2015, 02:22:54 PM

Title: Is it possible to have a properly balanced big bore big stroke motor?
Post by: JesseA420 on April 10, 2015, 02:22:54 PM

this was a recent conversation in the chatbox, maybe jerry or arlan could shed some more light onto this.

i was thinking, when stroking and throwing huge pistons into these motor, why arent the counterbalancers modified at the same time to properly offset the new bore/stroke vibes? wouldnt this solve the vibration issues? on big raptor motors the counter balancers are modified along with these monster +8 cranks and 108+ pistons and they are getting significant reliability gains from them.
ryan mentioned "The counter balancers should be modified to compensate for the larger cranks and pistons. However, the counter balancers would need to get larger, and there's no way to do that. There in lies the problem. I mean, there's always a way, but it may require far more changes to parts that people are willing to do."

would it be as simple as adding weight? because the lobes could be drilled and filled with heavier material, without increasing their size to an extent. or would changing positions of the lobes to compensate for the the changes across the whole rotational mass be needed?

Title: Is it possible to have a properly balanced big bore big stroke motor?
Post by: Burns363R on April 10, 2015, 02:48:56 PM

Like we talked about in chat.  The counter balance is meant to off set the weights on the crank in the horizontal plane.  The weights on the crank are meant to offset the weight of the piston.   Going larger on the piston would require more crank weight to off set it as well as more counter balance weight to offset the crank weight.

That being said, i dont thin the motors are perfectly balanced in stock form either.  The counter balancer weights seem to be much smaller, and run in a smaller diameter than the crank weights, which would mean they arent a perfect offset.  Maybe Jerry or Arlan can shed more light on this.

Title: Is it possible to have a properly balanced big bore big stroke motor?
Post by: F-Red on April 10, 2015, 03:32:17 PM

I wouldn't think you need, the equal weight on a counter balancer, as there is on the crank weight. If that was necessary, one could believe, Honda would have made a huge counter weight. Imagine what the motor would look like? :semi-twins::Boobies2: