I am in the process of changing the vacuum hoses on the throttle body, but I think my existing ones are on wrong?
The right hand hose on no. 3 is running up to the device in the photos (don't know what it is!)
The hose is being pointed to with the screwdriver.
That's the MAP sensor, all four TBs should link to it via the vacuum hoses. So if only one TB links to it, as I think you're saying. Yes they're on wrong.
There's a fifth hose that goes to the PAIRs valve if it's not been removed. If it has, that hose needs blocking to seal it.
Excellent, thanks mate. That would explain my poor running.
Assume they were messed with at the last service.
Will fire her up tomorrow
Well, that made remarkably little difference!
High revs she sounds OK, but on idle at 1100 rpm, not running smoothly at all.
I have cleaned fuel pump, changed the vacuum hoses, throttle bodies are balanced.
TPS reads 1115 to 2700.
Any idea what the STPS ohms should read? Measures at 2124 but does not change if I move it or the throttle.
Off the top of my head, 900. But check the manual to be sure, you can download it from the Download section on here if you don't already have it.
I posted the values on here a while ago, reads like the STPS has failed, especially if its not changing at all. From memory, it needs to read 3400 ohm down to 800ohm, abd its the top value that counts. Need to check though.
Think I have found an issue.
I appreciate this is moving away from my original subject!
When I remove the screws from the STPS, I can rotate it beyond the screw holes o get readings from 500 to over 4000. So in my mind, the sensor is working.
However, if I remove the STPS, the lug in side throttle body does not rotate when I move the throttle, so the reading on the STPS will never change.
I assume it should turn, as it does on the other side with the TPS removed.
Any thoughts?
The STPS has an actuator / step motor to move the shaft.
It does not move via the throttle handle itself.
If you rotate the plastic in the sensor the reading should change
Quote from: Blubber on Thursday, 30 April 2026, 05:38 AMThe STPS has an actuator / step motor to move the shaft.
It does not move via the throttle handle itself.
If you rotate the plastic in the sensor the reading should change
Oh,Darn it! Thought I had found a fault!
Yes it does, but to get the range required, it won't when the bolts are in.
Quote from: Idh on Thursday, 30 April 2026, 05:50 AMQuote from: Blubber on Thursday, 30 April 2026, 05:38 AMThe STPS has an actuator / step motor to move the shaft.
It does not move via the throttle handle itself.
If you rotate the plastic in the sensor the reading should change
Oh,Darn it! Thought I had found a fault!
Yes it does, but to get the range required, it won't when the bolts are in.
Sorry, just trying to clarify as this is getting well beyond my knowledge. I know the STPS doesn't drive itself. that shaft isn't moving, so does that mean the step motor isn't working?
Hey mate,
In the downloads section you can download the manuals that mention specific STPS Ω resistances when the STVs are fully open and when they're fully closed.
Before you do that however, I would recommend you to do the following in order to confirm if the STVs servo motor is working properly.
1. Remove seat
2. Remove side plastics
3. Remove bolts that hold tank in place
4. Move tank somewhere where you will have access to all 4 bolts holding in the air filter in place OR fully remove the tank if you're feeling like it
5. Remove the 4 bolts that hold the air filter mount in
6. Remove air filter
7. Then start turning the key in the ignition to the on position and listen to the STV motor do its work
8. Observe from the opening that is now created in the airbox cylinder #2 and cylinder #3 STVs run their priming cycle
The STVs should fully close, fully open, and then stay in their fixed position.
If that cycle is not completing, then that means your actuator motor ain't working.
Then, unplug your STPS sensor, and start measuring Ω resistances by pushing the valves fully closed and then fully open with one finger (reminding you that the Ω resistances are specified in the manuals you can find in the downloads section).
Quote from: Idh on Thursday, 30 April 2026, 05:55 AMQuote from: Idh on Thursday, 30 April 2026, 05:50 AMQuote from: Blubber on Thursday, 30 April 2026, 05:38 AMThe STPS has an actuator / step motor to move the shaft.
It does not move via the throttle handle itself.
If you rotate the plastic in the sensor the reading should change
Oh,Darn it! Thought I had found a fault!
Yes it does, but to get the range required, it won't when the bolts are in.
Sorry, just trying to clarify as this is getting well beyond my knowledge. I know the STPS doesn't drive itself. that shaft isn't moving, so does that mean the step motor isn't working?
The reading on the STPS needs to be done with the secondaries closed, you can either do this by removing the air filter and pushing them closed from inside the air box, or even simpler the linkage for them is under the throttle bodies slightly behind the STPS sensor, for both sensors the most important readings are those with the throttle closed, 1100 ohm TPS & 800 ohm STPS. After you have reset both you need to disconnect the battery for a minimum of 30 mins, do it with the lights switched on & the ignition to drain the residual energy in the system. When you reconnect the battery, switch the ignition on and fully open the throttle a couple of times before starting, this tells the ECU of the new settings
Quote from: Idh on Thursday, 30 April 2026, 04:29 AMThink I have found an issue.
I appreciate this is moving away from my original subject!
When I remove the screws from the STPS, I can rotate it beyond the screw holes o get readings from 500 to over 4000. So in my mind, the sensor is working.
However, if I remove the STPS, the lug in side throttle body does not rotate when I move the throttle, so the reading on the STPS will never change.
I assume it should turn, as it does on the other side with the TPS removed.
Any thoughts?
Quote from: Idh on Thursday, 30 April 2026, 04:29 AMThink I have found an issue.
I appreciate this is moving away from my original subject!
When I remove the screws from the STPS, I can rotate it beyond the screw holes o get readings from 500 to over 4000. So in my mind, the sensor is working.
However, if I remove the STPS, the lug in side throttle body does not rotate when I move the throttle, so the reading on the STPS will never change.
I assume it should turn, as it does on the other side with the TPS removed.
Any thoughts?
Quote from: Idh on Thursday, 30 April 2026, 04:29 AMThink I have found an issue.
I appreciate this is moving away from my original subject!
When I remove the screws from the STPS, I can rotate it beyond the screw holes o get readings from 500 to over 4000. So in my mind, the sensor is working.
However, if I remove the STPS, the lug in side throttle body does not rotate when I move the throttle, so the reading on the STPS will never change.
I assume it should turn, as it does on the other side with the TPS removed.
Any thoughts?
Quote from: Idh on Thursday, 30 April 2026, 04:29 AMThink I have found an issue.
I appreciate this is moving away from my original subject!
When I remove the screws from the STPS, I can rotate it beyond the screw holes o get readings from 500 to over 4000. So in my mind, the sensor is working.
However, if I remove the STPS, the lug in side throttle body does not rotate when I move the throttle, so the reading on the STPS will never change.
I assume it should turn, as it does on the other side with the TPS removed.
Any thoughts?
Just looking at the pictures that you added, it looks like the rubber cushion has come of the end of the sensor & is stuck around the shaft. I would carefully pull this out with a pick & put it back on the sensor before refitting, each time the sensor comes out & goes back it pushes the rubber cushion further in & restricts movement of the shaft. Also there should only be one cushion on each sensor, my STPS had two of the rubber cushions obviously a previous owner had replaced the sensor but left the old cushion on the shaft
Thank you!I will run through these ideas next week.
Quote from: Idh on Thursday, 30 April 2026, 04:29 AMThink I have found an issue.
I appreciate this is moving away from my original subject!
When I remove the screws from the STPS, I can rotate it beyond the screw holes o get readings from 500 to over 4000. So in my mind, the sensor is working.
However, if I remove the STPS, the lug in side throttle body does not rotate when I move the throttle, so the reading on the STPS will never change.
I assume it should turn, as it does on the other side with the TPS removed.
Any thoughts?
the end of the shaft should be ckean and have a slot in it that mates with the STPS, and thr o ring should be on the sensor,not inside the stps shaft housing. As said, you can manually move the secondaries from the linkage underneath, but the operation is via the stepper motor that sits between #2 and #3. An ignition cycle will actuate them, you can see it if as per above you remove tank etc or you can hear it if you listen carefully.
I have the air filter out. When I manually push the secondaries closed, the shaft for the STPS rotates, but when I turn the ignition on, nothing moves.
Quote from: Idh on Friday, 01 May 2026, 01:29 AMI have the air filter out. When I manually push the secondaries closed, the shaft for the STPS rotates, but when I turn the ignition on, nothing moves.
Just to add more, with ignition on, I hear the fuel pump priming etc. With a torch into the airbox, I can see that the valves don't move during this priming process. Closing no3 by hand does move the STPS shaft.
Quote from: Idh on Friday, 01 May 2026, 01:38 AMQuote from: Idh on Friday, 01 May 2026, 01:29 AMI have the air filter out. When I manually push the secondaries closed, the shaft for the STPS rotates, but when I turn the ignition on, nothing moves.
Just to add more, with ignition on, I hear the fuel pump priming etc. With a torch into the airbox, I can see that the valves don't move during this priming process. Closing no3 by hand does move the STPS shaft.
Ah, there's your fault right there. You have no FI light and any codes?
The STVs should cycle whenever you turn the ignition on and the fuel pump is priming.
I am not sure how to diagnose that but I believe that is something that is not easy to trouble shoot.
I would recommend you check from the right hand side of the bike, if the mechanism is also clicking moving, maybe it just slipped and turn without moving the STVs.
Lastly, I'd also make sure that all the cables and connectors are attached without continuity issues.
I leave it to the more seniors to answer more.
Cheers.
Quote from: imweirdimnotsocial21 on Friday, 01 May 2026, 05:08 AMQuote from: Idh on Friday, 01 May 2026, 01:38 AMQuote from: Idh on Friday, 01 May 2026, 01:29 AMI have the air filter out. When I manually push the secondaries closed, the shaft for the STPS rotates, but when I turn the ignition on, nothing moves.
Just to add more, with ignition on, I hear the fuel pump priming etc. With a torch into the airbox, I can see that the valves don't move during this priming process. Closing no3 by hand does move the STPS shaft.
Ah, there's your fault right there. You have no FI light and any codes?
The STVs should cycle whenever you turn the ignition on and the fuel pump is priming.
I am not sure how to diagnose that but I believe that is something that is not easy to trouble shoot.
I would recommend you check from the right hand side of the bike, if the mechanism is also clicking moving, maybe it just slipped and turn without moving the STVs.
Lastly, I'd also make sure that all the cables and connectors are attached without continuity issues.
I leave it to the more seniors to answer more.
Cheers.
Thank you. Will remove the throttle bodies I think. I can get a replacement from scrap dealers if need be. It's gone well beyond my knowledge !
And yes, when I started there was FI error, two codes showing errors in both sensors , but when I adjusted the TPS, they cleared
First thing, I take it that you have reconnected the big grey plug on the left hand side, where you will have been taking the sensor readings, this is where the stepper motor get it's feed from (apologies if this is stating the obvious) with this disconnected the secondaries will not operate
Also there is a connector on the right hand side of the stepper motor bottom of throttle bodies, this is the feed to the motor, it is held in place with either a Philips or a JIS screw, worth removing, cleaning & checking for voltage before removing the throttle bodies which isn't the most technical job but is certainly a bit of an awkward job to do - if you go that route read the how to and get a couple of flat pieces of sheet metal cut to size to make removing the bodies easier
Quote from: Idh on Friday, 01 May 2026, 05:28 AMAnd yes, when I started there was FI error, two codes showing errors in both sensors , but when I adjusted the TPS, they cleared
codes will always clear as the ecu is very basic and no capacity to store codes beyond 1 ignition cycle, so if you get a code and turn the bike off, the code will clear
It does sound like the stva motor has failed, or at least the drive to the shaft is not connected. There have been cases that the magnet oick up inside the stva breaks, so then the motor doesn't know where to turn to. Typical error codes would be C28 or C29
Quote from: Eric GSX1400K3 on Friday, 01 May 2026, 07:56 AMIt does sound like the stva motor has failed, or at least the drive to the shaft is not connected. There have been cases that the magnet oick up inside the stva breaks, so then the motor doesn't know where to turn to. Typical error codes would be C28 or C29
Thanks Eric.
Think I will open another topic on this, my initial hoses question has changed somewhat!