The usual recommendation when people complain that they're getting transmission jerks when opening or closing the throttle, is (assuming there's no mechanical problem) to practice smooth throttle inputs. That's sound advice of course, for various reasons besides off-idle jerks, but there's a problem that no amount of smoothness can address, as far as I can tell.
Smooth throttle inputs essentially boil down to (sufficiently) slow throttle inputs. In the context of throttle jerkiness, the critical phase, where smoothness is required, is while the engine is crossing the transition between braking and acceleration. Imagine opening the throttle "infinitely slow" while engine-braking. At some point the engine would cease braking and the motorcycle would coast at constant speed. At that point, any more throttle would cause the engine/transmission to freewheel until the lower run of the chain goes slack and the upper run goes tight, and all the gears shift a bit and after that point you start to accelerate. So during that transition, any more than absolutely necessary throttle will just allow the engine to pick up more speed while freewheeling and increase the jerk you'll get once the chain tightens again.
Assuming that is correct, one necessarily has to be slow. Ideally one could quickly open the throttle up to the critical point, then slow down until the transition is complete and then speed up again. That is perhaps possible to some extent when high up in the rev band, as then the point of torque reversal is far from idle. When going relatively slow though, that point is right off-idle and the only way I can avoid a jerk is to open the throttle slowly until I'm accelerating, which again often causes me to apply power later than intended. It's not a matter of technique, as far as I can tell, as I can apply throttle at various speeds, causing jerks of various intensities from silky smooth, to moderate, to jarring. It's just that, if you want to be smooth, you need to be slow.
I can see only one way out of this: opening the throttle prematurely, compensating for the delay until acceleration sets in. The problem there is that, while one is prematurely opening the throttle engine braking diminishes and one has to take that into account as well, to avoid overshooting your intended speed. Perhaps the necessary precision can be achieved through practice, but a different approach would be to overlap throttle roll-on and roll-off with braking. So when initiating braking for instance, instead of first fully closing the throttle and then applying the brakes, one could start applying the brakes either before or while closing the throttle, as needed, so that deceleration starts before engine braking sets in. Conversely, when accelerating, one can start opening the throttle prematurely, before fully releasing the brakes. The goal is to be able to cross the jerky-prone transition preemptively and "at leisure" while using the brake to control speed.
Well that is the idea. I've been experimenting for a while now with this and it sort of works. Much of the above happens semi-subconsciously now and I sometimes deviate from the strategy. For instance, when I want to reduce speed but anticipate that I'll soon want to accelerate again, I don't bother fully closing the throttle. Instead I keep it open at "maintenance throttle" so that it doesn't appreciably fight against the brake but doesn't help it either, which allows me to accelerate again or brake further if necessary without delay. In a turn, I brake before the turn as normal, but while releasing the brake I start applying throttle, so that by the time the brake is fully released, I'm already at maintenance throttle, going at constant speed and able to apply throttle at will without the possibility of a jerk.
I mention all this not as a great discovery, but because I haven't found it mentioned explicitly anywhere, with the exception of a book, where it was mentioned fleetingly, in the context of trail braking. I was wondering therefore, whether the more experienced riders among us use this technique, or something similar, either consciously or subconsciously, or whether they can think of any reasons to advise against it.
Smooth throttle inputs essentially boil down to (sufficiently) slow throttle inputs. In the context of throttle jerkiness, the critical phase, where smoothness is required, is while the engine is crossing the transition between braking and acceleration. Imagine opening the throttle "infinitely slow" while engine-braking. At some point the engine would cease braking and the motorcycle would coast at constant speed. At that point, any more throttle would cause the engine/transmission to freewheel until the lower run of the chain goes slack and the upper run goes tight, and all the gears shift a bit and after that point you start to accelerate. So during that transition, any more than absolutely necessary throttle will just allow the engine to pick up more speed while freewheeling and increase the jerk you'll get once the chain tightens again.
Assuming that is correct, one necessarily has to be slow. Ideally one could quickly open the throttle up to the critical point, then slow down until the transition is complete and then speed up again. That is perhaps possible to some extent when high up in the rev band, as then the point of torque reversal is far from idle. When going relatively slow though, that point is right off-idle and the only way I can avoid a jerk is to open the throttle slowly until I'm accelerating, which again often causes me to apply power later than intended. It's not a matter of technique, as far as I can tell, as I can apply throttle at various speeds, causing jerks of various intensities from silky smooth, to moderate, to jarring. It's just that, if you want to be smooth, you need to be slow.
I can see only one way out of this: opening the throttle prematurely, compensating for the delay until acceleration sets in. The problem there is that, while one is prematurely opening the throttle engine braking diminishes and one has to take that into account as well, to avoid overshooting your intended speed. Perhaps the necessary precision can be achieved through practice, but a different approach would be to overlap throttle roll-on and roll-off with braking. So when initiating braking for instance, instead of first fully closing the throttle and then applying the brakes, one could start applying the brakes either before or while closing the throttle, as needed, so that deceleration starts before engine braking sets in. Conversely, when accelerating, one can start opening the throttle prematurely, before fully releasing the brakes. The goal is to be able to cross the jerky-prone transition preemptively and "at leisure" while using the brake to control speed.
Well that is the idea. I've been experimenting for a while now with this and it sort of works. Much of the above happens semi-subconsciously now and I sometimes deviate from the strategy. For instance, when I want to reduce speed but anticipate that I'll soon want to accelerate again, I don't bother fully closing the throttle. Instead I keep it open at "maintenance throttle" so that it doesn't appreciably fight against the brake but doesn't help it either, which allows me to accelerate again or brake further if necessary without delay. In a turn, I brake before the turn as normal, but while releasing the brake I start applying throttle, so that by the time the brake is fully released, I'm already at maintenance throttle, going at constant speed and able to apply throttle at will without the possibility of a jerk.
I mention all this not as a great discovery, but because I haven't found it mentioned explicitly anywhere, with the exception of a book, where it was mentioned fleetingly, in the context of trail braking. I was wondering therefore, whether the more experienced riders among us use this technique, or something similar, either consciously or subconsciously, or whether they can think of any reasons to advise against it.