66mm Big Bore + rods. Do I need to rebalance the Crank?

[Fred659]

Hi,

Is it necessary to rebalance the 300 crankshaft if I put big pistons (66mm) and Carrillo rods as the crank is 180°?

I guess it would be better, but I try to understand how balancing a 180° crank works.

I can try to match the weights the best I can on the rod ends and pistons.

Can somebody who understand this help me?

Also, Wiseco 66mm piston, rings and pin + clips = 204g and I weighted a 250 one at 168g The Wiseco pins are massive...

does anybody know how much the 300 piston piston, rings and pin + clips weigh?

Can I put the 66mm pistons on the stock connecting rods?

Thanks you.

[Mohawk]

Stock 300 62mm complete (piston/ping/rings) is 157grams.
Wiseco 64mm complete is 198grams. So much for forged being stronger !
Wiseco 64mm with ZZR600 pin complete is 186grams.
ZZR600 64mm stock piston complete is 168grams.
Ninja-250 62mm stock piston complete is 167grams.

I have load tables for all of these at various red lines for comparison.
If I can whittle 4grams out of the Wiseco pistons to get down to 182grams complete then at 12k/rpm it will have the same load factor as a stock 300 @ 13k/rpm. Mine is for use in a Versys-X 300 big bore so lower redline.

You can view the load table in this thread which is my other project https://www.pb-evo.com/topic/78963-z...ort-300-build/

Yes you can put the Wiseco piston on the stock rods, but I'd suggest a lower redline to avoid damage. It's the TDC inertia number you need to worry about, as that is piston weight on exhaust stroke trying to rip the rod in two.

[Fred659]

Originally Posted by Mohawk

Stock 300 62mm complete (piston/ping/rings) is 157grams.
Wiseco 64mm complete is 198grams. So much for forged being stronger !
Wiseco 64mm with ZZR600 pin complete is 186grams.
ZZR600 64mm stock piston complete is 168grams.
Ninja-250 62mm stock piston complete is 167grams.

I have load tables for all of these at various red lines for comparison.
If I can whittle 4grams out of the Wiseco pistons to get down to 182grams complete then at 12k/rpm it will have the same load factor as a stock 300 @ 13k/rpm. Mine is for use in a Versys-X 300 big bore so lower redline.

You can view the load table in this thread which is my other project https://www.pb-evo.com/topic/78963-z...ort-300-build/

Yes you can put the Wiseco piston on the stock rods, but I'd suggest a lower redline to avoid damage. It's the TDC inertia number you need to worry about, as that is piston weight on exhaust stroke trying to rip the rod in two.

Tank you very much.

I can't lower the rpm cause it's for my race bike and I will need to gear longer and defeat the purpose of the mod. it lives at 12-14k

I did the inertia calculation with the 250 piston to compare and it was already at 20% more at TDC.

it's crazy, I think I have a 09 67mm zx6r piston and it's at 165g with everything on it... (0107 stamped on the top of the piston).

[Mohawk]

Yeah best bet for a 300 race bike big bore is the ZX6R pistons. Plenty of cheap second hand ones around &/or new from Kawasaki dealers. Thing to watch out for is I believe they changed the pin diameter in one of the new model years.

I'll be using ZZR pistons in my ZZR315 build as Wiseco are way to heavy. But they should be fine in my X300 build with lower redline & I'm after more torque anyway. Plus now I'll have spare pistons unless some else in UK wants some as I had them special ordered for delivery I can't send them back ☹️

[Fred659]

Just restating my first question here:

Must I dynamically (with bob weights) rebalance a 180° inline crank?

or

Do I only have to statically (scale weight) balance and match the rod ends and piston assemblies?

help would be really appreciated.

thanks.

[DannoXYZ]

No need to balance crank. But you should get balance-shaft re-done with higher weight pistons in mind and optimised for RPMs you'll be using most.