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Crank Balance Specs

Tonerjockey

Tonerjockey

High Miler
GT Contributor
Joined
Oct 28, 2008
Messages
788
Location
San Jose
Well I searched the site and still can't find this... I know it's here.

Can someone tell me the balance formula for the crank and moving parts on a G5? I also need the bob weight.

I seem to remember 60/40 from somewhere...

Geezeritus onset.

Alex
 
Just from memory, the balance factor is 52%, 26 grams? is allowed for oil in the hollow crankpin. Bob weight will be determined by piston assembly and con-rod weight.
 
Just to second Charlie's figure of 52%. Guzzi I think initially did it at 50% and after quite a while modified it to 52.

Changing the balance factor essentially changes the RPM where it vibrates - i.e. there is probably a different and optimal balance factor for an ambo versus a lemans. Balancing to the last gram, while it sounds great, is not of so much practical value in the real world as the weight of oil on the crankshaft is constantly changing as you rev, brake and turn corners. I would only bother if I was fitting new pistons and/or rods. It certainly can't hurt anything except your wallet.
 
For quite a while now I've been using the 51% figure appropriate to later models as per Guzziology. Happy with the results.
 
So I get about 1089.2 g for both pistons, pins, rings, and clips.
Big ends of both rods 786.9
Small ends both rods 459.5
52% of small ends + pistons etc 805.3
Plus big ends 1592.2 g

Put 26 g steel chunk into oil bore to compensate for oil.
Wrap 1592.2 g around journal (a little more that 3.5 pounds of lead strip held in place with weighed duct tape)

insatll flywheel and clutch cover.

let er rip!

we'll see how this works. Just gotta find some lead sheet or strip. I had some big-o-solder but only 2 pounds of it.

Alex
 
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