Semi lightened flywheel

[Turin]

Having the frame on my 850T powdercoated, and finally getting her cleaned up. Anywho, I found this treasure in my parts stash that came with my LeMans Racebike project, so onto the T it goes. Perfect for this mildly built engine.
Score!

[jwinwi]

Looks like a nice project!
Why does a lightened flywheel not need a specific amount of weight removed to preserve the overall balance of crankshaft compared to total rotating mass? I have always gotten lightened flywheels balanced to their ring gears to make the motor as smooth as possible.

[lucky phil]

Looks like a nice project!
Why does a lightened flywheel not need a specific amount of weight removed to preserve the overall balance of crankshaft compared to total rotating mass? I have always gotten lightened flywheels balanced to their ring gears to make the motor as smooth as possible.

Guzzi engines are internally balanced as opposed to externally. So the crank is balanced independently of the flywheel. As long as the flywheel balance is ok you can remove as much weight from it as you want. Ducati's for instance are a 90 deg V twin but have much lighter flywheels than a Guzzi which a silly heavy in my view unless you hauling a sidecar.

Ciao

[jwinwi]

Guzzi engines are internally balanced as opposed to externally. So the crank is balanced independently of the flywheel. As long as the flywheel balance is ok you can remove as much weight from it as you want. Ducati's for instance are a 90 deg V twin but have much lighter flywheels than a Guzzi which a silly heavy in my view unless you hauling a sidecar.

Ciao

OK, that makes sense but I've read that Guzzi cranks are balanced to something like 50% or 52% of the rotating mass which I understood to be flywheel, clutch and ring gear...

[Idontwantapickle]

OK, that makes sense but I've read that Guzzi cranks are balanced to something like 50% or 52% of the rotating mass which I understood to be flywheel, clutch and ring gear...

The percentage that you referred to is the balance factor. It is the percentage of the reciprocating mass (piston, rod, etc) that is attached to the crank throw while balancing the crank.
As Phil noted the Guzzi crank is balanced unto itself, all other items that rotate with it must also be balanced properly.
As a side note the balance factor can be a very closely guarded secret in the engine building world.

Hunter

[jwinwi]

The percentage that you referred to is the balance factor. It is the percentage of the reciprocating mass (piston, rod, etc) that is attached to the crank throw while balancing the crank.
As Phil noted the Guzzi crank is balanced unto itself, all other items that rotate with it must also be balanced properly.
As a side note the balance factor can be a very closely guarded secret in the engine building world.

Hunter

Got it. Thank you! 

[lucky phil]

The percentage that you referred to is the balance factor. It is the percentage of the reciprocating mass (piston, rod, etc) that is attached to the crank throw while balancing the crank.
As Phil noted the Guzzi crank is balanced unto itself, all other items that rotate with it must also be balanced properly.
As a side note the balance factor can be a very closely guarded secret in the engine building world.

Hunter

Yes it seems so. A 90 deg V twin is generally accepted to be a 50% balance factor but it can vary depending on crank orientation. I read a long time ago that Guzzi's were actually adjusted to 52% from the factory,dont know if thats true or when it happened,I'd need to research where that came from.
One interesting point is I'm not sure all car/multi cylinder engine balance people calculate the weight of oil in the crank pin when they balance a 90 deg twin crank. It makes a difference.

Ciao 

[Stevex]

Loosing some weight from my flywheel / ring gear made a hell of a positive difference to my LM2.
Plus, you get to put accurate timing marks on the flywheel 

Before:





After:

[Chuck in Indiana]

Grumble grumble.. I went to all the trouble to lighten one for The Kid.. and he's never got around to using it..

[kirby1923]

When I renewed the clutch on my CX the flywheel teeth were toast! So...

Replaced with a much lighter flywheel, 'bout 10 lbs.?? lighter, (had to do new marks for timing) and I gotta say it did improve things a considerable amount.

I'd say if your going to have to replace a flywheel I would consider a lighter one...

:-)

[larrys]

I paid Manfred Hecht to lighten the flywheel on my '83 SP. That, coupled with a B10 cam, Agostini cam gears, Bub exhaust, K+N's, and some head work it completely changed the personality of the engine. It had significantly more top end, and was way less tractable in traffic. YMMV.
Larry

[Turin]

My LeMans SE Flywheel