New crank - old counterweight - advice needed...

[lefty leif]

As my old crank looks like it was drug of the ocean floor, with rusted webs, journals in need of grinding, and the splines and threads pretty rough as wel, I've sprung for a NOS crank but will be using one of two bolt on counter weights i have.  The question is, does this automatically entail rebalancing, or is there a process i can use to determine if it is within a good range usable for street use?

thanks for any advice that can be given,

leif

[RichardL]

Leif,

After reading all of your previous posts, it seems that, as far as we know, you could be asking about a crank for a Honda 125. I probably won't be much help regarding the balancing but it would be nice to know the year and model of your bike so that those who know something have useful info. Pictures of your bike and your crankshafts would be great, as well.

That said, is your NOS crank complete and you just want to modify it? Or does it need a weight from your old crank to be complete? If the former, why bother? If the latter, knowing as little as I do about the process, I'd at least spring for static balancing.

..and now, ladies and gentlemen, people with experience in this area will now chime in.

Richard L.

[lefty leif]

Gotcha.  It's a 1962 A7.  It was bought as a basket case that looked decent, but after finding quite a few hidden horrors, it's been a way bigger and pricier challenge than i had expected.  I'll try and get a few photos loaded up soon - progress is slowly being made - and once I get the new crank in my hands, things should start moving along again... 

To answer your other question, I need the weight from my old crank to be complete - but when mix and matching like this I thought the  questioning of balancing would apply to ANY make and model? 

Being that I'll be getting a rebore, likely using oversize aftermarket pistons, the weights will be off of the originals, but from what I've read here - the small difference in weights for being oversize isn't seeming like a big issue to most.  But the difference in weight found between different counterweight lumps could be much more dramatic perhaps?

I'll try and get a few photos loaded up on the weekend of where its at so far...

leif

[KiwiGF]

To fit a used flywheel is probably quite unusual and it might be there is no one with experience of doing it so here is my 2 cents worth. ....

Im almost certain each flywheel is unique in that it is drilled by bsa to suit a crank "core" so, has yours been drilled?

of course it could be the cores and flywheels were balanced separately in which any flyweel will be ok on any core.....but i suspect thst is not the case .......

thats probably not much help!

[muskrat]

G'day Leif. The short answer is yes it will need to be balanced.
As KiwiGF said they are balanced as a unit (together).
The balance factor varies from make and model. 60 to 65% is the ball park figure.
Have a look here  http://www.a7a10.net/forum/index.php?topic=6086.0
Cheers