Counterbalance shaft gone

[dingleberry]

Have just removed counterbalance shaft on my 400. Didn't split engine, thought I'd be real clever and try to break bearing shell and knock out balls with a cold chisel and drift. Things deviated slightly from my grand plan when pounding on the left side bearing whole assembly disappeared into the case several inches. It had punched the shaft and right hand bearing through the alloy retainer taking the water pump gearshaft locating hole with it. "Golly gosh darn it!" were the words immediately uttered upon completion of this process. I think I could repair it with a bit of alloy solder, maybe. BTW the shaft and bearings weigh 1400g (3.08lb)

[fret not]

Oh my!  Things are evolving at your place.  Now what are you going to do?  I would guess either replace the motor with another, or split the cases and clear out the "debris" and make needed repairs.

3lb. of metal thrashing around inside the cases would cause some vibration and shaking, . . . . . unless it was smooth previously.  Likely to become a bit buzzy but not unmanageable.  We await your report on the 'improvement'.

[dingleberry]

I have two engines and this was the spare one so no big deal. I'm fairly sure it will repair ok. Well I'm hoping the 'improvement' will make it shake a bit then it will feel as fast as a loud exhaust sounds. I'm pretty sure it won't make much difference to power. Bring on those good vibes.... whatever happens won't be as bad as my A65 Thunderbolt.

[Rikugun]

Why remove the counterbalance system? I noticed POD's list of improvements also listed it's removal. Is this just for weight savings?

[The Prophet of Doom]

Removing weight is easier that gaining horsepower - but has the same effect (ie increased power to weight)  If that weight is rotational, then even more so because you have to overcome their inertia in 2 dimensions - hence lightened flywheels, pistons, balancer, wheels etc are hot topics in the go faster community.  If moving from a 550 to a 400 flywheel makes a difference, then dropping 1 1/2 kg will surely be noticeable.

If I remember correctly it was the Yamaha USA team ripped their balancer out - that's where I got it for my list - in one of the newsletters I think.

[dingleberry]

Just a reminder to all this project is not going to be my only ride, in fact it won't get used much at all so longevity is not an issue for me. Removing balance shaft will no doubt shorten engine life and I probably should have it all dynamically balanced, but I won't as that will cost money.  :o
The shaft itself doesn't have much 'throw' on it so possibly wouldn't make as much difference as reducing weight from the crankshaft. Weight taken farthest from centre of rotation has the greatest effect. Bit like bowling a cricket ball with a four foot long arm, you would need a strong shoulder I guess. 

[dingleberry]

Removing weight is easier that gaining horsepower - but has the same effect (ie increased power to weight)

Hmmm so when I trim my 400 down to 150kg it will have the same power to weight ratio of the 550  ;D
Shame the torque won't be the same.

[fret not]

Prophet, the racers did remove the balance shaft, AND dynamically balanced the crank shaft for the rev range of the power band.  Smooth enough at speed, lighter, and less stuff to fuss with whenever the motor comes apart, which can be often for a racer.

[The Prophet of Doom]

Thanks Fret, good to know my memory is not failing me too much.  I was going through those old newsletters this afternoon looking for the US Racing team notes - found mention of a guy who put RD400 6 speed gearbox inside his XZ.  Hmmmm, I wonder how hard that would be to do.

@Dinglebeery Torque:
XZ400    3.4 kg-m
XZ550    4.7 kg-m