Dealing with vibes

[Propellor]

the engine has had the balance shaft removed, however it "only" produced a 20% balance apparently.
have fitted a 35/36 tooth sprocket to the rear which has sorted the cruising revs nicely.
fitted a couple of small bar ends but i think they need a little more mass.

i havent heard of people making a top mount for the engine.

its still early in its "development" but usable enough for me to trundle about on it.

taking inspiration from

I might be getting confused here, apologies if so. But aren't there two balance shafts in the xl500? Like the 250RS? If so, do you mean the front one? Which is a "shaft". Whereas the rear one is on a bearing sat on the gearbox shaft, if my memory serves? But then that raises a question. If the front shaft is gone, then I assume the chain must be missing too? If that is the case, then the rear counter weight won't be driven either. It might even be removed? If any of that is right, then you might be 50% down, but at least you won't have a rocking couple! 

[Propellor]

If the balance shafts run at crank speed I wonder why the issue wasn't dealt with in the crank?

There is only one balancer on the XBR engine so it works like a 180 degree parallel twin........

I can see what you mean, but, assuming I've understood it correctly, there are lots of differences too?

The single cyl/single balance shaft setup creates a couple, as does the 180 deg twin, but the couple acts in a different plane and is a lot weaker since it is acting at only 50% mass? On the xbr the centre distance looks quite small, as you'd expect, so this will reduce the effect as much as possible?

The single balance shaft won't create any "extra" secondary vibration, like the alternately opposing crank assembly on a 180 deg twin would.

I'm wondering why Honda went away from a theoretically superior idea, in the form of twin balance "shafts", onto just one? Different frame design?

[guest564]

The single balancer is simpler, cheaper and easier to package, though the first versions were unreliable on a race engine until they changed the dampers on the backlash gear from two rubbers and two springs to four rubbers.