Smooth Throttle Transitions

[Michaelr11]

I'm fortunate to ride an R1100RT and also a couple of Airheads, a '74 R60/6 and an R100. I find that downshifting and rolling on the throttle during a curve is much smoother on the Airheads than I can manage on the Oilhead.

 

Is this a function of the carbs versus fuel injection? Any techniques or practice to improve my throttle smoothness - I ride the RT about 10K miles a year...should be getting better.

[David]

It could be less of a throttle issue and more about drivetrain lash. Here are a few techniques you can try:

 

1) Skip the clutch, just temporarily. Apply light pressure on the gear selector while you add throttle and it'll snick into place. That'll tell you exactly where the transition points are.

 

2) Use the clutch, but don't roll off on the throttle. Just fan the clutch with a quick movement while simultaneously downshifting. If you vary the duration of clutch disengagement, you'll find that place where the engine rpm rises to the perfect matching point.

 

Overall, the biggest reason for jerky throttle control during downshifting is rolling off on the throttle too much.

[Joe Frickin' Friday]

One problem may be excessive slop in the main throttle cable. For throttle body synch jobs on oilheads/hexheads, there needs to be some slop so that the throttle pulleys are positively resting on their stops when at idle. Once the synch job is done though, you can fiddle with the barrel adjuster at the grip to remove that slack so that the throttle grip doesn't rock back and forth freely.

 

Ideally you shouldn't be transitioning from engine-braking to power in the middle of a turn, but if you find cause to do so for some reason, getting rid of this slack can help make it less upsetting.

[ShovelStrokeEd]

Overall, the biggest reason for jerky throttle control during downshifting is rolling off on the throttle too much.

 

Ahmen to that statement. I almost never roll off any throttle when executing a down shift. In the lower gears, I may, in fact, add a bit. I regularly transition between two very different bikes. My Tuono has a 90 degree throttle and light flywheels which makes the throttle a bit touchy when compared to the 120 degree throttle on my Triumph Sprint. The Sprint also applies its torque in a more gentle manner than does the Tuono.

 

What I have found helps me is only using the muscles in my hand to operate the throttle. NO WRIST or arm motion needed. I can get 5-10 degrees of throttle motion by just rolling the throttle across my palm and fingers, thereby using much smaller and more articulate muscles for control.

[VinnyR11]

Overall, the biggest reason for jerky throttle control during downshifting is rolling off on the throttle too much.

 

.....What I have found helps me is only using the muscles in my hand to operate the throttle. NO WRIST or arm motion needed. I can get 5-10 degrees of throttle motion by just rolling the throttle across my palm and fingers, thereby using much smaller and more articulate muscles for control.

 

We're staying in the Berkshires for the summer, pretty much at the foot at Mt. Greylock. We got here a couple of days ago and I've been to the top 3 times already. On the steeper sections you need almost surgical precision with the throttle, and even then you feel some lash. (To be honest, I'm very anal about it though.) I also experimented with your "NO WRIST" motion, and it does help. I think it's a good suggestion.

 

I still think the throttle mapping on the RT's at low revs totally sucks, and it's compounded by drive lash.

 

Makes me wish for carbs again, except when I'm trying to start it in the dead cold, or after it's sat for a long while, or when I'm riding in changing altitudes,or... OK, I'll live with the lash, but I really wish it could be improved.

[russell_bynum]

Overall, the biggest reason for jerky throttle control during downshifting is rolling off on the throttle too much.

 

Ahmen to that statement. I almost never roll off any throttle when executing a down shift. In the lower gears, I may, in fact, add a bit. I regularly transition between two very different bikes. My Tuono has a 90 degree throttle and light flywheels which makes the throttle a bit touchy when compared to the 120 degree throttle on my Triumph Sprint. The Sprint also applies its torque in a more gentle manner than does the Tuono.

 

What I have found helps me is only using the muscles in my hand to operate the throttle. NO WRIST or arm motion needed. I can get 5-10 degrees of throttle motion by just rolling the throttle across my palm and fingers, thereby using much smaller and more articulate muscles for control.

 

Yup to all of that.

 

The Tuono is the most difficult bike I've ridden when it comes to making smooth on-off throttle transitions. Mine is worse than David's was (different pipe, different chip, a few other minor differences) but I think they're all pretty sensitive due to the power delivery, the engine braking, and the 90-degree throttle. The good news is once you master it, you can be smooth on any bike.

[TyTass]

I (a novice compare to these guys) was experiencing the same thing. It was driving me batty.

 

I've been practicing decreasing my right hand movement for some time and was beginning to question my abilities. Then I did what Mitch said above about taking all the slack out of the throttle (just after he and I spoke about it at BRR a few weeks ago). Believe me, that helped immensely.

 

Couple that with a Throttlemeister, where I dial just a tad a pressure in, and what a difference! It was much easier to focus on my right hand technique.

 

I spent the weekend in the WV twisties finding the right touch. And by the end of the weekend, I was far smoother even without any TM pressure dialed in. I guess it made me realize just how small of movements really are quite enough.

 

A better rider probably doesn't need the gadgetry but it certainly helped me.

[ShovelStrokeEd]

Damn Tuono! I have never ridden a bike that invites ludrcous amounts of throttle and then punishes you for it by either spinning the back tire or doing mid-corner wheelies. Thank Dog it has a chassis and suspension that will put up with this nonsense and allow you to live for another day.

 

When I am really paying attention, I can approach the level of smooth that the Sprint just so easily brings. 10 HP and 100 lbs make a big difference.

[russell_bynum]

Damn Tuono! I have never ridden a bike that invites ludrcous amounts of throttle and then punishes you for it by either spinning the back tire or doing mid-corner wheelies. Thank Dog it has a chassis and suspension that will put up with this nonsense and allow you to live for another day.

 

Yup...like I said...it's an axe murderer in a nice Italian suit.

 

Man I love that bike.

[russell_bynum]

I (a novice compare to these guys) was experiencing the same thing. It was driving me batty.

 

I've been practicing decreasing my right hand movement for some time and was beginning to question my abilities. Then I did what Mitch said above about taking all the slack out of the throttle (just after he and I spoke about it at BRR a few weeks ago). Believe me, that helped immensely.

 

Couple that with a Throttlemeister, where I dial just a tad a pressure in, and what a difference! It was much easier to focus on my right hand technique.

 

I spent the weekend in the WV twisties finding the right touch. And by the end of the weekend, I was far smoother even without any TM pressure dialed in. I guess it made me realize just how small of movements really are quite enough.

 

A better rider probably doesn't need the gadgetry but it certainly helped me.

 

I used to drag some rear brake in the tight stuff to keep tension on the driveline to reduce lash.

 

It doesn't work on the Tuono because, best I can tell, the rear brake on that bike is purely decorative, but it worked wonders on the RT at places like Deal's Gap.

[Spike]

Another option would be to set the bike up before corner entry. Have your entry speed such that you don't need to continue the decel after your turn in point. Here you can keep the throttle just positive enough to keep your current rate of speed which will keep the slack out of the drive train. When you are ready you smoothly twist and drink the resulting endorphins.

 

 

 

 

[ElevenFifty]

On my 1150, the chop off of the throttle has always bothered me. I ride at higher rpms, fan the clutch, pre-load the shifter ... all of that helps.

 

When I'm really hooning it up in the twisties, I'll slip the fast idle lever up ... just like when I start the bike in the morning. The result is that my 1100 RPM idle, goes up to 1500 or so ... the throttle 'chop' is gone and shifts are smoother even if I screw up.

[Penforhire]

I do think it partly a FI versus carbed issue. Mosty FI systems just don't taper off and on as smoothly. I've read about newer FI systems that compensate and smooth out throttle response.

[MotorinLA]

I ride a R1200RT-P as my assigned Motor, but occationally I have to take out a spare R1150RT-P. It takes a little while to re-adjust to the driveline lash, as it is very pronouced on the 1150 compared to the 1200. I can sympathize with the OP, as much of the riding I do involves heavy acceleration followed by heavy deceleration. The 1150 definitely demands a much smoother throttle transition to minimize the driveline lash.

[Hollow Road Rider]

I am not sure what "driveline lash" means here and I have seen it referred to before on this same issue. I would guess it has something to do with the freeplay of flexible driveline parts at their joints? How's that for a wild guess from a Special Ed teacher?

[Joe Frickin' Friday]

I am not sure what "driveline lash" means here and I have seen it referred to before on this same issue. I would guess it has something to do with the freeplay of flexible driveline parts at their joints? How's that for a wild guess from a Special Ed teacher?

 

Not particularly the flexible parts, which would be just the rubber element in the driveshaft and the torsional shock absorber on the gearbox input shaft. There is also slop/clearance in every meshing-gear pair (that's at least two pairs in the gearbox, and one in the right-angle final drive), and there is also slop in the splines that lock the gears to the shafts in the gearbox when you select any particular gear; without that last slop, you'd have a helluva time getting it into gear.

 

To see how all this adds up, put the bike on the centerstand, and put the gearbox in first gear. Now grab the rear wheel with your hand and rotate it in either direction; you should get a couple of inches of rotation at the tire tread. That's the sum total of the driveline lash, and doesn't incorporate the distortion of the flex elements described earlier (you'd have to really grab the wheel and rotate hard to feel that).

 

When you are engine-braking (in gear but off throttle), all of that slop is stacked up in one direction. If you whack the throttle open, the driveline rapidly winds up in the other direction; because of that "running start," it builds up a little bit of speed before it slams all those parts together and closes all those gaps. Taken to an extreme it's hard on the driveline, but even if not taken to an extreme, it can really upset the chassis, something you don't want when you're leaned over hard in a turn.

 

If you're still having trouble conceiving of it, try this experiment:

 

1. Stand your wife in the middle of the room.

2. Stand next to her, making snug contact with her shoulder.

3. Close your eyes.

4. Push harder.

 

Everything's fine, right? Nice gentle transition from very light load to heavier load; she doesn't get upset. This is analogous to starting a turn with just a smidge of throttle already applied: all of the driveline slop is already taken up in the correct direction, and adding more throttle is no problem at all.

 

Now try this:

1. Stand your wife in the middle of the room.

2. Close your eyes.

3. Tell her to take a couple of steps away from you.

4. Now put your shoulder forward and move toward her (your eyes are closed, right?) until you make contact.

 

Like it or not, you're probably going to make harder contact with her than you'd like; she's gonna get upset, might even lose her balance. This is analogous to the transition from engine-braking to acceleration. It happens every time you transition from braking to power, and your best bet is to have it happen before you get leaned over hard. If you really have to do it while leaned over, make sure you get on the throttle gently at first to take up all the driveline slop, then start adding the real power you're after.

 

 

[Groanup]

Nice!

 

I've heard driveline lash explained before, but never better than that.

 

Now to test it out. Hope the wife is in a good mood...

[Hollow Road Rider]

Thanks, that was a perfectly sensible explanation.

Now the next question is, why the R1200 referred to earlier has so much less driveline lash?

[philbytx]

Hey Brad

 

What do you mean "EVEN if you screw up"!