How I eliminated the twitchy throttle

[D.A.]

[EDIT (MAY 5, 2021): TO SEE THE FINAL VERSION OF MY MODIFIED R6 THROTTLE CAM, ALONG WITH A PRINTABLE TEMPLATE YOU CAN USE TO CUT YOUR OWN CAM, GO DIRECTLY TO PAGE 4 OF THIS THREAD.]

WARNING: Make any modifications to OEM equipment at your own risk!

 

@bartman5impson @seven @rfmueller

This is a follow-up to a post I created a few months ago called I'M STILL CONFUSED BY THE FUEL CUT ON DECEL ISSUE:

(https://fz07.org/thread/13334/im-still-confused-about-the-fuel-cut-on-decel-issue/#comments)

That thread was about my frustration with the twitchy throttle on my stock '17 FZ07.

After doing a bunch of maintenance-related work (installing new chain / sprockets, new spark plugs, new air filter, syncing throttle bodies, adjusting everything that's adjustable, etc.) I sent my ECU off to 2WDW for flashing. 2WDW provides impeccable customer service and very fast turnaround. I shipped my ECU from NC to 2WDW in Washington State on a Friday via USPS Priority Mail and had it back on my bike the following Thursday.

Post-flash, it's nice to have the fan come on at a lower temperature and I'm quite satisfied with the amount of engine-braking, which feels like it's been reduced by about 30% – a level that provides plenty of braking to slow the bike down but isn't so drastic it throws you onto the tank if you suddenly release the throttle.

I did not, however, detect an increase in overall power, which makes having to pay an extra 70¢/gal. for premium fuel to accommodate 2WDW's timing advance a little annoying. Power delivery in the upper RPMs feels less linear than it did before flashing. The bike has less pull at idle, meaning pre-flash I could cruise around in a parking lot at 6 mph with the throttle closed and my fingers off the clutch, whereas post-flash the engine will lug or stall if I try that. And worse, there was no noticeable reduction in twitchiness, which is the sole reason I had it flashed. I talked to 2WDW and while they were really cool about it, they ultimately admitted there's nothing more they can do via flashing to reduce twitchiness.

To be fair, without the ability to do quick A/B comparisons between stock and flashed ECUs, it's impossible to conclude for certain there is zero difference in twitchiness. On the other hand, if a change is so subtle the rider cannot feel a difference, it might not be worth the hassle and expense of making the change. If I had it to do over again, I would probably buy the FTECU interface instead of having the flash done so I could make changes at home incrementally – e.g., first eliminate the Fuel Cut On Decel, ride the bike to check the effect, then make the next change. I'm sure 2WDW would have happily made changes in that manner but repeated cross-country shipping and time delays would have made it impractical.

Also, performance-wise my bike is completely stock. Based on what other forum members have posted, it seems likely the results would have been more dramatic had I installed an aftermarket air box and exhaust system. 

Anyhow, with the ECU flash not proving to be the solution, I came up with the following combination of tweaks to reduce the twitchiness to a level I can accept:

[1]  tightened chain to the minimum spec of 51mm (so there's zero drive lash)

[2]  increased idle speed to 1400 RPM (the goal being to prevent the throttle from ever closing completely)

[3]  tightened throttle cable to the point where it starts to bind when the bars are at full lock (so the throttle responds instantaneously to even the most minute input)

[4]  "tamed" the throttle grip cam

In regards to Step 4, although there are pre-made throttle tamers available on the market, I decided to custom cut my own by modifying an R6 throttle grip:

For comparison's sake, this is the cam wheel on the stock throttle tube:

 

This is an unmodified R6 throttle tube:

 

I used a Dremel saw to cut a deeper groove and reshape the profile:

 

This shows the modified groove. You can't tell from the photo but the new groove dips lower than the hole for the throttle cable (as well as lower than where the cable rides in the FZ's OEM cam):

 

And the photo below shows the final profile (but keep in mind the new cable path implied by the profile is not the same as the actual path created by the groove, which is slightly deeper, as illustrated in the photo above):

 

I am not smart enough to calculate the optimal cam shape before modification so I did it the old fashioned way – I experimented by cutting progressively deeper and steeper grooves, installing the grip on the bike, riding it and repeating the process until settling on what you see above.

Although it doesn't eliminate it 100%, the modified cam radius greatly reduces snatchiness when transitioning from closed to small throttle openings by spreading the transition over a greater area and the abrupt increase to the larger radius means power comes on strong once you get moving. The only drawback is you have to twist the grip further to reach wide open, so while the stock grip requires about a 90° rotation and an unmodified R6 grip a 60° rotation, this mod puts you at around 78°.

Edited May 31, 2021 by D.A.

[robbo10]

Well done with the throttle. A snail cam.  Now why could Yamaha not do that?

[D.A.]

I had created a second version as well. The disadvantage of this one is that it does not have as dramatic of an effect on reducing off-to-on throttle snatchiness. The advantage, though, is it has minimal effect on rotation, increasing the R6 cam's closed-to-WFO twist from 60° to only about 65°.

Marked it for drilling:

 

New profile after drilling (and deepening the groove using the Dremel saw as illustrated in my previous post):

[Pursuvant]

Excellent analytics and practical applied mod, thank you D.A.

Is your second mod, your preferred mod that has addressed twitchiness with only 5 degrees additional rotation?

I'm going to pick up extra throttle tube and throw away grips to experiment with your preferred before springtime.

Which one do you recommend trying first? Should this mod be done on R6 tube only (because it reduces rotation b4 you start mod)  or can it be applied to stock tube (without stock tube twisting too far for full throttle)?

Ok, I can see the stock tube is not optimum for this mod, start with r6 tube.

Edit

No dremel saw, I have to think about a manual way to do this - i.e. triangular thread file, or dremel saw blade hand operated like a file

Edit - looks like my pvc hand saw has same teeth and cut width as dremel blade

Edit - you can lay two hack saw blades together (hold them with your hand), they cut the correct width also and promote going slow and careful

Edited December 12, 2020 by Pursuvant

[seven]

@D.A.

Well this post is making me have some mixed emotions. I just pulled the trigger on the 2WDW tune last week because of all the hype everyone here had for it for solving the twitchy throttle and providing smooth power across the power band. The good thing though is that I am not doing the mail-in service as I am in Canada. I will be loading the 2WDW tune via FTECU so that I can swap tunes as needed. 2WDW will provide the required tunes based on mods to the bike and as they change I can increase my file library so I will be able to swap between tunes to find what works best. Regarding the fuel, I already use Shell 91 which is ethanol free so there shouldn't be much of an impact there other than the decrease in mileage that I hear people talk about.

Regarding the throttle tube modification, I was thinking of something like too and I am surprised that this has not been addressed in the aftermarket or by someone with a design application and a 3d printer. This might be something I start to look in to. I am not all that concerned at this point about the amount of twist as so far I am fine with the stock setup. I do like the idea of customizing the R6 grip to have a more personalized throttle profile.

[D.A.]

5 hours ago, Pursuvant said:

Is your second mod, your preferred mod that has addressed twitchiness with only 5 degrees additional rotation?

In terms of chronology, I initially created the version that involved drilling a new hole, then made the one that did not get drilled but did get a shaved-down profile. I currently have the shaved / non-drilled version installed on my bike because it is more effective at reducing throttle snatchiness.

The dilemma is trying to figure out where exactly on the cam the modification needs to be made to achieve optimal results. I initially assumed it would be adjacent to the hole for the accelerator cable. That seemed like the most logical spot. However, after drilling the new hole and testing the result on the bike (without making any other changes), I discovered it had no discernible effect on throttle response. So I progressed to the next step of sawing a deeper groove.

After several tests, I came to the realization the spot on the cam that coincides with the initial throttle opening has no bearing on where the cables attach but is instead determined by where the accelerator cable begins to wrap onto the cam, which I estimate to be about 45° from the hole where it attaches. But that's largely a guesstimate. I came up with that calculation by installing the throttle tube, cables and cable housing onto the bike and trying to visualize where the free portion of the accelerator cable starts to wrap onto the cam. The problem is once you assemble everything, there's no way to see exactly what's happening inside the housing because it's opaque, creating a Catch-22. Hence the guesstimate.

I'm sure there are smarter people on this forum that can calculate the precise spot where a modification needs to be made. If one of them chimes in with an exact specification, I will gladly modify another throttle tube based upon it.

Edited December 3, 2020 by D.A.

[Pursuvant]

1 minute ago, seven said:

2WDW tune last week because of all the hype

The ECU flash has genuine value, don't let perceptions pull you away from recognizing the bike is factory "lean" and 2wdw corrects that, and more.

I'm glad I can flash and not have to endlessly monkey withe the maps via computer. I have had enough changing/testing needle valves and main jets for a lifetime

[Pursuvant]

2 minutes ago, D.A. said:

I'm sure there are smarter people on this forum that can calculate the precise spot

This mod is the bomb, thank you. Great fun because the effects will be so in your face obvious. On my list for off season mods

[Pursuvant]

Can I be lazy and ask some one to post the r6 year and Yami part(s) numbers for anything that I should have on hand to start this mod please?

[D.A.]

14 minutes ago, Pursuvant said:

Can I be lazy and ask some one to post the r6 year and Yami part(s) numbers for anything that I should have on hand to start this mod please?

Only thing you need is the 2006+ model R6 throttle tube (which comes with a rubber grip pre-installed). It's part # 2C0-26240-00-00 and is a direct swap for the OEM throttle tube/grip. The only caveat is you will have to adjust the throttle cables where they attach to the throttle butterflies to create more slack since the R6 throttle tube cam has a larger diameter wheel than the FZ's.

And yes, to answer your previous question, the mods I outlined in this post are not really doable with the stock FZ throttle tube – unless, that is, you could come up with a way to build up the FZ cam's profile rather than trim down the R6 cam's profile.

At $20.93, Partshark has the lowest price I've seen on the R6 throttle tube/grip:

Yamaha 2C0-26240-00-00 - Grip Assy : Part Shark

 

[D.A.]

1 hour ago, seven said:

Well this post is making me have some mixed emotions. I just pulled the trigger on the 2WDW tune last week because of all the hype...

This is precisely why it took me so long to follow up regarding my flash. 2WDW is a forum sponsor and I enjoy the forum, so saying anything derogatory about their services is essentially biting the hand that feeds me.

Part of my disappointment with the flash is no doubt due to my expectations being heightened as a result of the near-universal praise by other forum members. But it sounds like the route you're taking will provide the best of both worlds.

Edited December 3, 2020 by D.A.

[seven]

1 minute ago, D.A. said:

This is precisely why it took me so long to follow up regarding my flash. 2WDW is a forum sponsor and I enjoy the forum, so saying anything derogatory about their services is essentially biting the hand that feeds me.

Part of my disappointment with the flash is no doubt due to my expectations being heightened as a result of the near-universal praise by other forum members. But it sounds like the route you're taking will provide the best of both worlds.

For sure. And I am keeping an open mind because everyone has different expectations and opinions. I am still hoping that it will solve the issues I have without introducing new ones. So I won't fret about it now as it is still 4 to 5 months before I will be able to get back on my bike anyway.

[D.A.]

1 hour ago, seven said:

... Regarding the throttle tube modification ... I am surprised that this has not been addressed in the aftermarket ...

I'd initally thought I came up with the idea but after creating my first prototype, discovered throttle tamers are already available in the aftermarket (as mentioned in my first post in this thread).

I think custom-cutting them has allowed me to more precisely zero-in on a fix that addresses my specific bike's issue but at $79.95 (also available from Amazon w/ free shipping) this one looks to be a great alternative:

G2 Street Tamer Throttle Tube | Yamaha

---

The G2 Street Tamer Throttle Tube for Yamaha improves control of over-responsive power characteristics of most fuel injected...

 

Edited December 3, 2020 by D.A.

[D.A.]

Graves makes them too but theirs requires modification to the OEM cable housing:

Progressive Throttle Tube ZX10 ZX6 R1 R6 R3 FZ09 FZ10 XSR900 MT-10 Graves Motorsports

---

Graves Motorsports R1 + R6 + R3 + FZ09 + FZ10 + ZX10 + ZX-6R + MT09 + MT10 + XSR900 Progressive Throttle Tube is designed to...

 

Edited December 3, 2020 by D.A.

[Pursuvant]

19 minutes ago, D.A. said:

G2 Street Tamer Throttle Tube

 

We can make our own and out-do the Tamer- it probably smooths to much.

I want to build a profile that solves the just off idle, then comes on hot right at 4 grand where the motor is already rapidly climbing up on top of the torque curve.

Got my r6 tube on the way

[DewMan]

When I got my FZ-07 new the snatchiness of the throttle just off idle was throwing the overworked suspension into a tizzy every time due to me being >200LBs on the stock suspension. I got the 2WDW flash and it corrected the issue enough that I was happy to get an R6 throttle tube and to this day I'm happy with the combo.

The final correction was to upgrade the suspension front and rear to correctly support my weight. I have no complaints about the handling of the bike now for my admittedly non-aggressive riding style.

I just wanted it known that not everyone is unsatisfied with the 2WDW flash as it pertains to just off idle throttle response. 

[D.A.]

2 hours ago, Pursuvant said:

... Got my r6 tube on the way ...

Nice! 
You might want to install the R6 tube on your bike and ride before making any mods so you understand why people like it so much!

[D.A.]

1 hour ago, DewMan said:

... I just wanted it known that not everyone is unsatisfied with the 2WDW flash as it pertains to just off idle throttle response. ...

I realize I am clearly in the minority in that regard!

[Pursuvant]

D.A., here's a model of my understanding of your alternative design, this looks like it would give the best low throttle response modulation (better than stock tube) and then transition to R6 throttle response quite nicely, but must be something here I don't see because it became your "alternate".

 

Stupid draw up, but (in terms of rpm) A is "idle", B is about 3.5K rpm, B to C is no change - no affect on throttle, C (3.5K rpm) is the start of the transition from smooth throttle to quick twist, and full quick twist at D  (around 4 K)

 

Legend:

A to B: gives the best smooth throttle modulation (with this throttle tube) from idle to 3.5K

B to C : does nothing to change throttle open amount, no change in throttle, to rider the throttle goes from point B to C instantly and starts the new C to D response curve. It's as if the "A to B curve is attached directly to the C to D curve" from the throttle cable perspective.

C to D : transition from smooth throttle to R6 full quick twist

E: cable exits the handlebar housing

 

I won't have the R6 tube for a few days, so maybe there is something that will become obvious when I get it that will kill this model?

Edited December 4, 2020 by Pursuvant

[D.A.]

3 hours ago, Pursuvant said:

... here's a model of my understanding of your alternative design ...

@Pursuvant:

I like what you've done!

I do, however, see a couple of issues.

First off, in reality the accelerator cable spools off the cam in the opposite direction from what you've drawn, meaning it starts at the mounting hole, then goes counterclockwise.

Second, you need to take into consideration that once installed, about 20mm of accelerator cable remains wrapped around the cam at all times, including when the throttle is closed. Once you start rotating the throttle, the next few millimeters of accelerator cable – which is suspended freely inside the throttle housing when the throttle is closed – begins to wrap onto the cam. It is at this juncture that the throttle transitions from closed to slightly open, so this is where the cam should transition from small radius to large radius.

The off/on transition occurs between points C and D as you've drawn it, but C is actually 1100 RPM and D is about 1400 RPM. Prior to C the throttle is still closed, with the portion of cable that goes from the mounting hole to point C serving no purpose other than to maintain proper cable alignment on the cam.

It's hard to explain in words so I will take my throttle housing apart tomorrow and snap some photos to show you what's happening inside. That should make it much clearer.

[bartman5impson]

Wow, excellent write up! @D.A.

[Pursuvant]

2 hours ago, D.A. said:

@Pursuvant

 

It's hard to explain in words

Woke up by the dog to go out at 2am, my brain must have worked on it in my sleep because my first thought was "it's not going to work like that".

One note, I drew it as if I was at the bar end, looking towards the throttle housing, that's why it's backwards (in this view the acceleration turns my drawing counter clockwise).

I have to wait till I have the R6 tube in hand and can see how the cable wraps and starting position of throttle relative to the housing cable entry point, like you are saying.

Back to sleep...

[Dennis.Halmstad]

Excellent! I to feel the throttle twitches and its not near the level of smoothnes I would like when opening the throttle  midcorner. I have tested riding and trying to really never close the throttle completely going in the corner and staying there until its time to open it in the corner but this only reversing the problem if you accidently close it and then it gives you more engine break when you arent ready for it.

Have read somewhere regarding early days of fuel injection on bikes that the throttle position sensor had delay or har to read on this very small openings from the bottom. Resulting in moore air to the engine but zero fuel because the sensor werent reading yet, and then all of a sudden it might jump from 0% to 5% and then read correctly up to wide open. This would make the bike lean of and then a great jump in power at the time you want precision. Dont know if this might be the case on these bikes?

One other theory would be looking on the fuel map, if you are mid corner closed throttle you might be in the fuel cell of 0% tps and 5000rpm resulting in zero fuel, then when you open the throttle.. How much fuel does the first cell after 0%tps at 5000rpm give? Should this be smoother? leaner? richer? or is there some magic calculation thats supposed to smooth this out when coming from zero tps?

My mind would say smoother transition and leaner fueling there but some people say this gets better with any enrichement device?

I dont know, all just a guessing game. Would be nice if some wizard on fuel tuning could throw their 2 cents here. Maybe someone has recorded this situations that can dismiss the tps theory?

[robbo10]

5 hours ago, D.A. said:

@Pursuvant:

I like what you've done!

I do, however, see a couple of issues.

First off, in reality the accelerator cable spools off the cam in the opposite direction from what you've drawn, meaning it starts at the mounting hole, then goes counterclockwise.

Second, you need to take into consideration that once installed, about 20mm of accelerator cable remains wrapped around the cam at all times, including when the throttle is closed. Once you start rotating the throttle, the next few millimeters of accelerator cable – which is suspended freely inside the throttle housing when the throttle is closed – begins to wrap onto the cam. It is at this juncture that the throttle transitions from closed to slightly open, so this is where the cam should transition from small radius to large radius.

The off/on transition occurs between points C and D as you've drawn it, but C is actually 1100 RPM and D is about 1400 RPM. Prior to C the throttle is still closed, with the portion of cable that goes from the mounting hole to point C serving no purpose other than to maintain proper cable alignment on the cam.

It's hard to explain in words so I will take my throttle housing apart tomorrow and snap some photos to show you what's happening inside. That should make it much clearer.

As you taking it apart, I wonder whether you might: cut a piece of card to show the profile you have cut; and some references like the profile of the ouside of the flange, and positions of the holes.  Then post a pic. Unless you think that is a stupid suggestion!

[Pursuvant]

3 hours ago, robbo10 said:

As you taking it apart, I wonder whether you might: cut a piece of card to show the profile you have cut; and some references like the profile of the ouside of the flange, and positions of the holes.  Then post a pic.

Let's work with D.A. it's his design. When I have my best effort I will send it to D.A. for his tweeks and then he can publish, cause this is D.A. all the way, I'm not doing anything new or novelle here.