Continuing - So what did you do to your bike today...?

[SpongeBob]

For those who would be tempted to complain that the good ol'14 maintenance is a difficult task: here is what it takes to simply adjust engine's idle RPM on my Suzi's garage mate, an MV Agusta Brutale.
No less.
(note that vacuum plugs for synchronization are conveniently placed on the sides of the bike for an easy access  )

[grog]

Induction noise on those worth every hassle Bob. Incredible ride.

[Eric GSX1400K3]

For those who would be tempted to complain that the good ol'14 maintenance is a difficult task: here is what it takes to simply adjust engine's idle RPM on my Suzi's garage mate, an MV Agusta Brutale.
No less.
(note that vacuum plugs for synchronization are conveniently placed on the sides of the bike for an easy access  )

I see your Brutale and raise you a BMW, this was for removing the front and rear suspension shock absorbers....

[Hooli]

I've been thinking about my C28 error and how it fails.

Initially the STVA is correct, doing the normal movement when the ignition is turned on.I get fast idle when the bike starts but then the fast idle climbs as the STVA goes to full rotation and then the code appears.
Now it says elsewhere in the manual that the ECU only knows the position of the STVA by comparing the TPS and SPS readings, which makes sense as there's only two wires to the STVA.
I think I've got a failed SPS so the ECU isn't seeing any movement from the STVA. Therefore the ECU flags a STVA error.
I'll test the SPS later but might end up getting a replacement anyway. After all it's original and I'm on my third TPS, none of which tested faulty when they failed.

let us know how you get on, with mine the error comes up at random on a ride, seems after a sudden throttle opening, like when overtaking. I get proper fast idle and it then settles down to 1100 rpm once warm.

If I'm gentle with the throttle it won't pop up, but if I'm turning the wick up, it seems to occur.

Yeah it wasn't that, proved it with some fiddling on friday. I did have one of the plastic T-pieces in the vacuum hoses snap when I touched it so I replaced all them, didn't help though.
So I ignored it for the weekend & rode my tractor. It's getting annoying now as I still can't find what's wrong with the damn 14, the manual just says replace the throttle bodies & ECU but that seems a touch drastic & expensive.

[Speedy1959]

I thought "Just for fun" I would remove my springs and drain / refill the shock adjuster oil (plus replace those silly security fill bolts with stainless allen bolts.)..

[Hooli]

Was it fun?

[Speedy1959]

Was it fun?

It was a damned sight more "fun" than re greasing the head bearings which I did today..

[Hooli]

I've been thinking about my C28 error and how it fails.

Initially the STVA is correct, doing the normal movement when the ignition is turned on.I get fast idle when the bike starts but then the fast idle climbs as the STVA goes to full rotation and then the code appears.
Now it says elsewhere in the manual that the ECU only knows the position of the STVA by comparing the TPS and SPS readings, which makes sense as there's only two wires to the STVA.
I think I've got a failed SPS so the ECU isn't seeing any movement from the STVA. Therefore the ECU flags a STVA error.
I'll test the SPS later but might end up getting a replacement anyway. After all it's original and I'm on my third TPS, none of which tested faulty when they failed.

let us know how you get on, with mine the error comes up at random on a ride, seems after a sudden throttle opening, like when overtaking. I get proper fast idle and it then settles down to 1100 rpm once warm.

If I'm gentle with the throttle it won't pop up, but if I'm turning the wick up, it seems to occur.

Yeah it wasn't that, proved it with some fiddling on friday. I did have one of the plastic T-pieces in the vacuum hoses snap when I touched it so I replaced all them, didn't help though.
So I ignored it for the weekend & rode my tractor. It's getting annoying now as I still can't find what's wrong with the damn 14, the manual just says replace the throttle bodies & ECU but that seems a touch drastic & expensive.

I still haven't fixed this BUT following some more research online I came across this thread on a GSXR forum https://www.gixxer.com/threads/c28-c29-with-a-confirmed-working-stva.557586/ Now their setup is slightly different to ours, on a GSXR the STVA & SPS are in the same unit fitted to the end of the throttle bodies, hence all the fix videos you see show a four pin connector being soldered up. But they work in exactly the same way, all the bits on the bike look the same ECU etc wise so it's the same kit mapped differently with a few packaging changes.

Now in that linked thread someone called TheGeek says

There are multiple circuits in the system. A loose connection on any of them can cause the ECU to think there's a problem. The logic of it all is really simple, but easy to confuse.

C28 can be caused by open circuits of the STVA, or unexpected data from the sensor.
C29 can be caused by open circuits or data out of range.

Two identical circuits on the STVA not shared with any other system on the bike. Direct lines to the ECU. I've seen loose sockets on both ends of the wiring harness cause C28 issues. These can usually be found by manipulating the wires at the coupler to cause or eliminate problems.

The STPS is where most people get confused. On the 06/07, there are three wires on the sensor. Black, yellow, and blue. Blue is the power input, black is ground, and yellow is the pickup. The manual has tests for the STPS, but in my opinion was written by a moron. Some of the conditions they want you to test for can't exist.

In essence, the sensor is just a variable resistor. Resistance across the Black and Blue wires should be static. I've seen readings anywhere from 4.3k Ohms to 5.5k Ohms. As the wiper rotates, it picks up a voltage. The further the wiper is from the power input, the lower the pickup voltage. This is why you test across the Yellow and Blue wires for calibration. What I've seen in some cases is that the sensor gets contaminated and has a short across the wiper pads. When this happens, you basically get a parallel resistor circuit with one resistor being variable. You can diagnose this by seeing a change in the static circuit with movement.

Most of the time, you'll see the secondaries try to open and then move back to closed at half speed and chatter. This is because the ECU is getting data from the STPS that doesn't match what it's telling the STVA to do. Since it sees the sensor, and data from the sensor in the expected range, it assumes the STVA is the problem and throws a C28.

So what I did was follow his logic & test my SPS for variable resistance between Blue & Black, which isn't a test in the workshop manual as far as I recall. I get exactly the same variable resistance on Blue & Black as I do on Blue & Yellow. So I've got the fault he describes. Which means my original logic quoted was correct, I just hadn't found why it was happening because I'd trusted the manual and not thought of this fault.

Prior to this I'd poked two wires in the back of the ECU connector & run them down to the connection at the bottom of the STVA, therefore eliminating the entire loom & proving the issue wasn't a wiring fault.

So it looks like I do need a SPS after all. I might try & convince someone I know to let me borrow theirs so I can prove it before I order one, but at least I can finally see a problem to explain what's going on. A dirty/worn SPS also explains why it's been an intermittent fault for ages too, same as I've had when TPS fail. They are exactly the same thing after all.

[grog]

Hooli, a good spray out with contact cleaner?As long as wires/connections ok, its just a contact running over a board. Works on old Bosch air flow meters, fuel senders etc. Same principle.

[Hooli]

Hooli, a good spray out with contact cleaner?As long as wires/connections ok, its just a contact running over a board. Works on old Bosch air flow meters, fuel senders etc. Same principle.

Sealed unit Grog, you can't get anything into working parts of the sensor. It's the black one on the RH side of the throttle bodies.

[Nic]

My new Delkevic 420 trioval slipon arrived, the reason I bought it was that the Staintune was sounding like truck compression braking every time I changed gear not to mention decelling down a hill. Put the new Del on, same deal, put the Bazooka back on, same deal.
After doing some searching on this wonderful forum I discovered that having slack in your throttle cables will give you engine braking from hell and yes, I had quite a bit of slack, tightened them up and presto, no more truck compression braking noise, also worth mentioning that the Bazooka robbed so much power and with the Delkevic the bike goes really well, better than with the staintune. A lot of misery but bliss in the end thanks to the good folk here, yee haa, oh and I love the sound of the Del  Wish there was more bike talk here though, just sayin.

[grog]

Hey Nic, all those adjustments on 14 take a while but turn a great bike into an unreal bike. TPS, throttle cables, head brgs etc etc, you know what i mean. If all set correctly makes huge diff as you just found out. Mine originally was supposed to be perfect settings from factory then Suzuki dealer services.Nothing was right.It is now, i find once done, they hardly vary from perfect.

[Nic]

Thanks Grog, from a bloke who was a bike mech at a Honda dealer in the 70s you'd never think throttle cables would do that, it's all new to me and I agree, I can't believe how much better it goes with the Del slipon, now that the horrible BLAAAAA noise is gone it's a new bike, it's been this way for all the 3 years I've owned it but it's only just recently really got up my goat and it was driving me mad, when the new muffler made no difference, well, you can imagine, so now the bike is just better again, awesome.

[grog]

The list of adjustments is all needed. Mine runs so well it amazes me time after time. External filter my best mod, revs to the top. Diff slip ons certainly make a power increase. I have three, the Yoshi increases mid range is very noticeable.

[Tony Nitrous]

Ordered a dealer mode switch for the Gen-3 Busa. Brings up fault codes, resets service counter etc.

Normally I'd just jump the pins with a Paperclip, but the 3 has a bunch of wires and pins and I thought I'd treat it.  Cheap switch and a few wires, but having the right plug and being pre-made suits clumsy lazy old me.