Chasing a clunk: am I crazy?

I've put about 4000 miles on my 750 since getting it running this summer, and while I've ironed out a lot of issues, one (of a few) persists: I find it VERY hard to ride smoothly. No matter how slowly and smoothly I get on or off the throttle, there's a rough bump that moves the whole bike, and it's getting to be a major annoyance now that I ride for work. I'll try to describe my issue.

I've taken apart my second engine (shaft, same as my current running engine) to some degree and I think I've traced my issue to play in the transmission; when I turn the inner clutch basket, it has roughly 30 degrees of play before turning the output. There's virtually no play in the bevel gears and no discernable play in the driveshaft; I just replaced the dampers in my clutch basket and it made no difference.

I'm trying to figure out the details involved in switching to chain drive, and while I'm at it I'd like to see if I can tighten up this issue. Could it be that my transmission (about 22k miles old) has become so worn that there's a harsh slap when it engages? I'm frankly at my wit's end. I love this bike to death, but the roughness is driving me crazy.

Thanks to any who have anything to say about this; I appreciate any thoughts on what might be going on. Alternatively, if every KZ rider has their spines jostled when they get on the throttle...nevermind! :silly:

30 degrees of lash is huge. that is definitely a problem. There should be very little lash in the transmission. I'm not familiar with the differences between the shaft and chain driven models but this is how you check lash, unfortunately it requires splitting the cases, but you maybe able to do it though the oil pan

>>>>>>>>>>>>>>No matter how slowly and smoothly I get on or off the throttle, there's a rough bump that moves the whole bike, and it's getting to be a major annoyance now that I ride for work. I'll try to describe my issue.
More info please.
Releasing clutch from start in 1st gear, what happens ?
Same or different in all the gears ?
Roughness accelerating, steady speed, slowing down the same ?
Describe roughness with more detail.

There are rubber cush bumpers in the secondary shaft sprocket, clutch hub, and rear wheel, all of which could be contributing. On my 750 where was a lot of lash in both the secondary shaft bumpers and in the clutch hub. I'm not sure if that's what's going on here, but maybe.

@DoctoRot: I was afraid I might need to pull it apart. I suppose it'll keep me sane while the roads are salted!

@73z1: Releasing the clutch slowly mitigates most of the jolt. The effect is the same in all gears - there's a jolt when I let off the throttle and a strong jolt when I get on the throttle. While moving positions - accelerating or decelerating - it feels smooth, it's just going to or from zero throttle.

@Nessism: Thank you for informing me, I missed that in the parts diagram. Judging by eye that looks like the amount of play I have, and I think (or hope) that it's more likely than my entire transmission being worn that badly already. I'll pick up the dampers in preparation for my future teardown.

Lock the front sprocket and recheck for play. Whats the oil look like?