Balanced Crank?

CDH have a good crank.

there is no perfect balance factor on a single cylinder engine but most are balanced to the 50-55 % factor for most engines.
I wish our little china girls were at 50-55% factor,stock is maybe around 10% and with further weight reduction (drilling it out) two holes between the factory ones 12mm dia and 15mm deep will get it to around 25% and 14mm dia same depth gets it to around 30% and that works quite well 40 -50% can be done but it starts to affect torque.
 
I wish our little china girls were at 50-55% factor,stock is maybe around 10% and with further weight reduction (drilling it out) two holes between the factory ones 12mm dia and 15mm deep will get it to around 25% and 14mm dia same depth gets it to around 30% and that works quite well 40 -50% can be done but it starts to affect torque.

What’s sort of rpm are you at streets?

The cdh cranks seem to rev real nice around 7000, but this is just estimates from speeds I’m doing
 
What’s sort of rpm are you at streets?

The cdh cranks seem to rev real nice around 7000, but this is just estimates from speeds I’m doing
My current engine with race ratio at 2.72 hits 10,200 -10,300 and on the street I use a 2.36 ratio and keep it around 8,000 -8,500 because its better on gas and Im still doing over 60.
 
are you saying the 40% factor works better for the high revs or we have trouble balancing them to 50-55
 
are you saying the 40% factor works better for the high revs or we have trouble balancing them to 50-55
Getting to 50% starts to affect the rotational mass and loses inertia needed to maintain sufficaint torque,and yes you need to take out alot of meat to get to 50% or more like 65 g worth.The 40% factor works great for true high flow, high output builds with good torque and will run much smoother than stock through out the range,30% is more commenly used and spins quite smoothly to high rpm but most importantly doesnt beat up the engine and helps it last much longer all around.And Its much easier to attain.
 
The old timers method of using a "balance factor" isn't accurate which is why the correct balance results in a different "balance factor" for different engines.
That is why a made a spreadsheet calculator that uses all the different weights (piston, rod, bearings, pins, etc) to calculate both the vertical forces and the rotational forces and shows you a graph of the forces throughout 360 crank degrees so you can see how close or how far away it is from the best possible balance. Then you enter various balance hole sizes till its as good as it will get. see http://www.dragonfly75.com/motorbike/vibes.html
 
The old timers method of using a "balance factor" isn't accurate which is why the correct balance results in a different "balance factor" for different engines.
That is why a made a spreadsheet calculator that uses all the different weights (piston, rod, bearings, pins, etc) to calculate both the vertical forces and the rotational forces and shows you a graph of the forces throughout 360 crank degrees so you can see how close or how far away it is from the best possible balance. Then you enter various balance hole sizes till its as good as it will get. see http://www.dragonfly75.com/motorbike/vibes.html
LOL your too much!The balence factor still requires a spread sheet and uses all the riciproacting mass weight vs the rotational and any engine can be balenced at a 20% factor or 30 or 40 it doesn't differ from engine to engine that's ridiculus 20-40% is 20-40% then end result is the same!Old timers method? This method is still the most used home mechainic's way of doing it themselfs.Just check out 2 stroke stuffing's video here and what everyone whom doesit this way (easier) instead of yours is wrong?Try telling that to all the race teams that also use this method LOL.How many engines do you have that spin 11-12 grand smoothly?
 
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