Question TRYING to solve the snatchy throttle

[skelly]

I don't have a haynes manual for this bike but if it follows the usual arrangement for bikes of this era, fuel is delivered to a common rail where the injectors prevent the fuel from entering the cylinder until a small electrical pulse operates the solenoid within the injector. The pressure of the fuel in the common rail is typically around 2.5-3 bar but this acceptable pressure is maintained by a fuel pressure regulator which is attached or is an integral part of the common rail, it's job is to return fuel back to the tank if the pressure gets to high. Inside is a spring operated piston with a needle that sits inside a valve and also controlled by a diaphragm that is operated by a vacuum. Fuel delivery is a fine balance and even a small leak at any of the vacuum lines can cause all sorts of problems including response lag, erratic idle, poor pick up etc. Again I can't be sure of the exact lay out of the fuel delivery on this bike ( I really must get a manual ), but lots of the sensors that send signals to the ECU rely on pressure variation. If you do decide to check the vacuum lines be meticulous, even a small crack at the end of a line can cause a poor vacuum. I hope you find a solution.

 

[Piggy]

I don't have a haynes manual for this bike but if it follows the usual arrangement for bikes of this era, fuel is delivered to a common rail where the injectors prevent the fuel from entering the cylinder until a small electrical pulse operates the solenoid within the injector. The pressure of the fuel in the common rail is typically around 2.5-3 bar but this acceptable pressure is maintained by a fuel pressure regulator which is attached or is an integral part of the common rail, it's job is to return fuel back to the tank if the pressure gets to high. Inside is a spring operated piston with a needle that sits inside a valve and also controlled by a diaphragm that is operated by a vacuum. Fuel delivery is a fine balance and even a small leak at any of the vacuum lines can cause all sorts of problems including response lag, erratic idle, poor pick up etc. Again I can't be sure of the exact lay out of the fuel delivery on this bike ( I really must get a manual ), but lots of the sensors that send signals to the ECU rely on pressure variation. If you do decide to check the vacuum lines be meticulous, even a small crack at the end of a line can cause a poor vacuum. I hope you find a solution.

Hi there

This is one system used but as I said in a previous reply, this is a dead head system I believe.

So the pressure regulator is inside the fuel tank. The pressure is constant at the rail at idle or full throttle 10k rpm. No return line or vac lines.

 

[Gary in NJ]

Have you confirmed the fuel pressure?

 

[Piggy]

Have you confirmed the fuel pressure?

Hey Gary.
Not as yet

It's a good idea to do this but I can't help but think it's nothing to do with fuel pressure. It's not a fuel pressure like problem...
It's common with lots of fz6's and has been (from what I've read) since new.
I've got no issues with high load, high rpm running... Where fuel pressure is most demanding. . . So I'm struggling to see why at the point of almost least demand, the fuel pressure would drop? Does that make sense?

 

[Gary in NJ]

Diagnosis is a process of elimination, so checking the fuel pressure allows you to either find something or eliminate as a possibility.

While I can think of many reasons why the fuel pump, filter and regulator could effect fuel pressure both at high and low demand, I’m only guessing without empirical data.

What I see in your video is a delayed fuel or ignition response - you are describing it as a “snatchy throttle” but that is the symptom, not necessarily the cause.

 

[Piggy]

Diagnosis is a process of elimination, so checking the fuel pressure allows you to either find something or eliminate as a possibility.

While I can think of many reasons why the fuel pump, filter and regulator could effect fuel pressure both at high and low demand, I’m only guessing without empirical data.

What I see in your video is a delayed fuel or ignition response - you are describing it as a “snatchy throttle” but that is the symptom, not necessarily the cause.

Yeah for sure.

I don't disagree with the symptom rather than the cause.

I will try and test it. I just don't have any doubts. Fuel rail pressure would be at 100% when you shut the throttle. Crack it open, fuel is ready for the injectors...

I'll try and get a gauge safely on it. I'm a bit concerned about fitting one and riding in case of a leak!!

 

[Gary in NJ]

Check post number 9 on the thread below. Cocoloco has proven himslf to be a master mechanic, and his diagnosis of his TPS (heat soaked vs cold and in diagnostic mode vs dynamic) may have reference to your issue.

Strange Idle Issue

I've been having some issues with my 2004 FZ6 idling. When I turn it on cold, it idles around 1600-1800 (I set it there, more on that in a bit). I ride it for a bit and the idle stays the same. However, after about 10-20 minutes of riding, it idles around 2500-3000 RPM. After riding for about an...

www.600riders.com

 

[Piggy]

Check post number 9 on the thread below. Cocoloco has proven himslf to be a master mechanic, and his diagnosis of his TPS (heat soaked vs cold and in diagnostic mode vs dynamic) may have reference to your issue.

Strange Idle Issue

I've been having some issues with my 2004 FZ6 idling. When I turn it on cold, it idles around 1600-1800 (I set it there, more on that in a bit). I ride it for a bit and the idle stays the same. However, after about 10-20 minutes of riding, it idles around 2500-3000 RPM. After riding for about an...

www.600riders.com

But he experienced none of the symptoms I am .. and I've experienced none of the symptoms he has?

 

[Gary in NJ]

But he experienced none of the symptoms I am .. and I've experienced none of the symptoms he has?

You didn’t take note of the TPS looking good statically but not dynamically?

 

[Piggy]

You didn’t take note of the TPS looking good statically but not dynamically?

It doesn't mention how he read the tps while riding though?

Mine reads fine with engine running/idling. And no delay on tps/throttle when stationary in neutral

 

[Gary in NJ]

It doesn't mention how he read the tps while riding though?

Mine reads fine with engine running/idling. And no delay on tps/throttle when stationary in neutral

Your TPS reads as OK through the diagnostic tool...Cocoloco found that method to not show the problem he suspected in the TPS. You might want to ask him how he took the reading.

 

[FinalImpact]

Piggy, I added a post in your other thread with a link to changes made to my S2 to fix the issue. I would assume a tune to PC3 would resolve this but that is not what I have. Follow the link.

 

[TownsendsFJR1300]

Welcome back stranger!

 

[FinalImpact]

Welcome back stranger!

Hi Scott. Ya, it's been a while! Life took me on ride and just been busy as hell and had to set priorities closer to home. Then add COVID and the impact to nurses which I live with it and walla - my disappearance!

It looks like many are still here holding the fort down and my password still worked! Imagine that! lol

 

[Motogiro]

Randy!

 

[Cumnz4U]

I have not rode a bunch of different bikes but I actually think it's a thing. So much so I did a search on here to see if anyone else noticed it & bamm, there are 3 pages of discussion. If I really think about it & roll slow I can get a smooth response but a lot of times it's like you are going from 0% to 10% instantly. I have never gone WOT but so far everywhere else in the throttle feels smooth to me except right there at the start. I feel like I am going to damage something in the drive train cause I equate it to reving up your car engine & then slamming it into drive.

 

[TownsendsFJR1300]

Are you referring to going into first gear from a stop?

 

[Gary in NJ]

I equate it to reving up your car engine & then slamming it into drive.

This sounds more like clutch technique than throttle technique.

 

[MattR302]

Late to this thread, but back when I had my 2007, I found that the G2 throttle tamer, along with removing all the slack from the throttle cable, made a very noticeable difference. Not 100% but definitely helped.

At the time, I had a CBR600F4 track bike, it was carbureted and the fueling was absolutely perfectly smooth. After riding that bike at the track all weekend, I REALLY noticed the poor off/on throttle transition on the FZ6 on the ride to work Monday morning

 

[Cumnz4U]

Are you referring to going into first gear from a stop?

No, anytime I change gears. I let off the throttle to shift, after shifting it won't let me slowly roll into the throttle. I can probably explain it better with an analogy. Say the throttle goes in increments of 0-10. Zero being idle & 10 being WOT. I feel like mine goes from 0-2 or 3 instantly. Hope that makes better sense.