Fast idle

[Eric GSX1400K3]

Download the manual from here, it's all explained there.  You can actuate by hand from the linkages under the throttle bodies. The primary you reach from inside the airbox

[Persizi]

I did everything as expected. I adjusted the STP resistance - 0.8Kohm on fully closed secondary throttle.
On a warm engine with agusted rpm to ~1100, I adjust the resistance of the TP to 1.1Kohm.
Then I tried to set up the fast idle but max voltage that I get is 1.15V with fully open secondary throttle valve. What I do wrong?

[t4underc4t]

having looked at the excellent instructions on voltage and the screw I have tried a few times to get this sorted now. On the second attempt, I wound the adjustment screw out so much that it came loose! this has led me to the following conclusion... (wish I has taken pictures) between the adjustment screw and 'metal plates' of the throttle bodies there is a small spring. It seems the issue is that the small spring over time looses its 'spring rate' and therefore, even if you allow the metal plates to separate by adjusting the screw, the spring no longer lifts the throttle plate with the force it requires. Its going to be quite fiddly to get it in place. However I will see what I can find although it may now be later in the year as I want to get out riding will the weather is starting to improve. 

Looking at the suzuki parts it seems to be item 15 on this microfiche. which is called a Torsion Spring

[Hooli]

I had a problem with the springs doing the same job on each TB being too weak once, but only because I'd lost them & replaced them with the wrong ones that were too weak.

What I have had there is the arm the screw presses against seizes on it's pivot & the return spring it's got can't keep it against the end of the adjustment screw. It's a right faff to strip the TBs down just to pop that off & regrease it, but it fixed the issue for me.

[BaNZ]

So I did some research on TPSes setting and have some material (and problem) to discuss.

I set TPS for 1.153v closed (it's 1.278 - 4.43Ohm TPS range), right after ignition turns on STVA moves throttle blades so voltage on TPS rises up to 1.203v (for cold start). Fully open secondary throttle gives 1.242v on TPS. I know it's not very correct values (I want my bike to be a bit more throttle responsive), but nevertheless I got fast idle from 2100rpm for 30 seconds.

But after fast idle ends engine idles on 1000rpm and want to die. If I hit the killswitch and then try to start again, there will be struggle for it. Eventually  engine starts but on 500rpm or so, then slowly rises to 1100. Same problem persist with hot engine, but not so prominent.

(I tried all of this with right TPS values after wiping ECU memory - same story).

Sooo... what it wants and what I'm doing wrong?

[Andre]

But after fast idle ends engine idles on 1000rpm and want to die

At that point I would increase idle speed to 1100. Let it run for a couple minutes, turn off and let it sit to cool completely and observe on next start.

Another point, I'd go with standard settings as a base.

[Eric GSX1400K3]

As Andre says  std settings. The lower 1.1V /1100ohm is more important than the top settings. Takes a bit but you can get it bang on or just over, say 1.12 1.14v.

Another issue with the STVA is the little magnet inside can break, causing issues.  A good check is to watch the StVA actuate as yoy turn the ignition on, it should cycle through its range of motion.  If it doesn't, or is jerky, could be the magnet or the mechanism needs a bit of lubricant.

[Hooli]

Use the correct settings, setting it wrong just makes it run worse. You won't get more throttle response that way.

[grog]

Agree with above, not sure how or why you thought better throttle response? Turn it faster/harder, youll get response

[BaNZ]

I see your point, guys.

As for TPS adjustment, the idea to fool ECU with main throttle blades angle, so it will inject more fuel for same amount of air.

[Hooli]

As for TPS adjustment, the idea to fool ECU with main throttle blades angle, so it will inject more fuel for same amount of air.

So it'd just run too rich...
More fuel doesn't equal more power unless it's running too lean & these don't tend to do that.

[Will14]

Can of worms this in my opinion & from my own past experience. Once the fast idle screw has been altered it throws all other settings out, trying to get back to standard took a lot of time consuming trial & error adjusting, checking, running allowing to cool and testing again. Before I altered the fast idle screw I marked its position & counted the number of threads on the screw that were visible from the underside, I could then return to the original starting point, every time I did go back to original I found I was getting different readings which seemed strange   

[BaNZ]

Hm... Okay then.

Well... Could someone explain meaning of this text from manual? (Section 4-65 fast idle adjustment).

[Hooli]

Not a clue, I couldn't make sense of that bit either. Hence I did mine by trial & error.

[KiwiCol]

If they had just broke it down a bit more, it would have read better.  My take on interpreting this procedure is:

1) Set the TP sensor to the correct voltage, write this down.

2) Once you've set that, open the secondary throttle valve slowly until the STP sensor voltage is reading 3.6v. 

3) Hold (somehow?) the secondary throttle valve at that exact position where it reads 3.6v.

4) Whilst the secondary is held in the above position, check the TPS voltage output. You're looking for a variation of 0.035v from step 1. when the STP sensor has a reading of 3.6v.

5) If the TPS is not showing 0.035v difference, adjust it by turning the Fast Idle Screw to get the desired result of 0.035v.