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Discussion Starter · #1 ·
I have a 1999 ST Sprint and am trying to complete its 12,000 mile service. I have done the valves which required one change of an inlet valve. I have a Carbtune to set the throttle bodies and also had to make up some adaptors push on adaptors so I could get the carbtune set up correctly. I've linked the tank up to operate whilst off the bike and the engine is nice and warm and I have to unscrew the idle air control valve so I can get to the adjustment screw on cylinder 2. Anyhow both cylider 2 and 3 are out so I adjust until the 3 levels on the carbtune are the same. All is going well until I try and connect the idle air control valve back up. The plunger has moved out slightly and I cannot get the unit to fit inside its housing so the mechanism can be screwed back onto the bike. What does one do ? How do I get the plunger to depress slightly so the whole lot can be screwed back on ?

Many Thanks
Scotty
 

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Scotty, have you got any pictures? I have an 04 and on that you don't need to touch the IACV to get at the TB screws.

Does yours not look like the one in this thread?

http://www.triumphrat.net/sprint-forum/35232-has-anyone-tested-their-idle-air-control-valve.html

If you have to move the IACV, the whole unit should be removable. They do not really like being taken apart. The plunger is operated by a stepper motor in the housing so you may find it has been trying to move the plunger to 'control' the idle while not inside its housing.

Rexx
 

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Discussion Starter · #3 ·
Thanks Rexxy

I've looked at your pic and my idle control valve is totally different being on a 1999 bike. Its necessary to totally remove it to adjust the throttle body screw on cylinder nos 2.

The problem I have is the plunger has opened on the idle control valve and therefore I cannot get the plastic housing to fit over the control valve so it can be screwed back onto the bike. Is there a way of getting the plunger to depress ? Its controlled electronically via the bikes computer. Is there a sensor I can blow into or something which will make the plunger depress ? i don't want tio use force to force the plunger back. Has anyone got any ideas as I would really like the bike to be running this weekend as I hav'nt had a run out in ages.

Thanks
Scotty:)
 

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You should be able to "force" the plunger down. It will move. Then when you assemble it and turn your key on, it will extend to the closed position, then retract and open up. That's how mine works on my 02, but I AM ASSUMING IT WORKS THE SAME ON THE 99. If I'm wrong, please let me know.
 

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Discussion Starter · #5 ·
Thanks Charlie. I've just been out in the garage and got this sorted. I screwed the white plunger cap in and that seemed to depress the plunger sufficient enough for me to get the screws fixed up. There is a bum piece of advice in the Haynes manual here that says the screw should be torqued down to 12NM. When I did this I split the plastc housing that the motor/plunger assemply fits into so I loosened off the screws and will leave it at that. I will probably have to replace the plastic housing sometime in the future but its good enough for now with the bike ticking over properly again.

Balancing the throttle bodies would be far easier on the newer 955i bikes I think as the idle control valve can stay in place all the time. Well its done, that's the main thing and will run much better now as the throttle bodies were out, especially cylinder nos 3.

I was hoping to fit a Scott oiler tonight but it has'nt arrived and I don't want the hassle of taking all the parts back off the bike so its going to sit in the garage until the Scott oiler arrives. Scott oilers..................a great invention from Scotland. Check their website.

Thanks
Scott:)
 

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Scotty,

Did you say your IACV does not look like the one that rexxy referenced to on the other thread? Only I have a 99 sprint as well and it looks the same as the pictured.
 

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Discussion Starter · #7 ·
Hi Quik d. That's interesting. They must have changed the design very early on. My bike could have been one of the very first ones to be made. My set up is definitely different and the unit has to be removed to get to the throttle body screw on cylinder nos 2.

I also adjusted the front pre load tonight as I feel the bike is too soft on the front and also adjusted the pre load and damping at the back too. One thing I'll say about these bikes...........the fairing sure helps to keep muck off the engine etc. Its really good removing a dirty fairing to see a nice clean engine bay area.
 

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Discussion Starter · #8 ·
Just checked Rexxys picture again and the set up here is totally different and much superior to the one on my bike and its the reason my throttle bodies go badly out of synch after about 6,000 - 7,000 miles. The throttle body adjustment screws on my bike are spring loaded ie the screw passes through a spring before screwing into the housing. The screws are on the top of the unit and not below. With engine vibration its probably easier for the screw to turn and go out of adjustment on my bike as its really only a spring thats tensioning it. It looks like the newer models have screws that fix directly into the housing and these would stay in tune longer as it would be much harder for them to turn with engine vibration.
 

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Discussion Starter · #10 ·
The problem is that the spring itself turns which in effect turns the screw. Applying silicon or locktite to the screw would only secure the screw head to the spring which turns with the vibration anyhow. Its no real problem only that I have to re do the throttle bodiees every 7,000 miles or so. At least its better than my old BMW R1100s which needed the throttle bodies balanced every 2k :eek:
 

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hi scotty, hope you can help a fellow scot and T-Nut -
i have a 99 st and i guess mine is the same setup as yours - did the same thing as well and cursed myself for 5 mins then went through the same procedure as you.
Can you offer any advice on stepper motor positioning ? I replaced the hoses - cracks everywhere and when i put mine all back together it would seem that my iacv is staying in the closed position as the bike idles roughly and dies....
I guess before the hoses were so perished, it still sucked a little air to help it tickover now it idles worse than before.
cheers
Dell
 

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If the idle air plunger is free to move, yours may have bound up, the startup cycle sets the position. Say the number of stepper motors step from full open to full close is 40 (I don't know the actual number) than at startup the ECM will drive the stepper ~45 steps force it to full closed. Any additional steps just stall the motor, this doesn't hurt it, but it does find the closed position. The ECM then starts counting stepps from there and knows 40 steps is full travel. So it doen't matter where in the travel you leave the plunger after reassembly. If you cycle the power on, on a bike assmbled per the above photo you will see the IACV do it's thing, also this is one of the sound you hear everything the ignition powers up.

On newer bikes that don't have the IACV, the stepper driven throttle stop does the same thing.
 

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cheers banger good to know what is going on, i definately think the problem is with the stepper, cleaned and lubed up but still the same issue here are the full symptoms
The bike once heated up ticks over great no issues and is strong at 1250. If i leave her for a couple of hours to fully cool down she fires again first crack, however a few secs afterwards and she starts to die, almost like the stepper motor remembers its last position then resets and closes air to the TB's. If i keep the butterflies open slightly for a min or so the bikes starts to smooth out and runs sweet again.
There are no MIL lights and i am lost for a reason to this
hope you can help
cheers
Dell
 

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Does it idle OK after it's fully warmed up, even if you have to use the throttle to keep it running so it can warm up? Once Wamed up and you are riding with engine well into the RPM's does it run ok?

I would tear things back down to the level of the above photo and make sure the IACV does stroke smoothly at power up. It there is any binding you should see it here. Reassemble making sure there are no air leaks. Rember when you blip the throttle to keep it running the ECM sees this via the throttle position sensor and adds fuel. If there is a air leak around the IACV there is no way for the ECM to know and add fuel, thus it will be too lean to idle. Also, as you are keeping it idling with the throttle you are likely over shooting the 1250 rpm set-point and the ECM is driving the IACV closed to maintain 1250. Maybe that's what you are seeing?

Also rember I could be totally wrong; I am an engineer after all. It's like trying to be a mechanic with my head up my own ass....:D
 

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thanks guys for all your help, gonna lift of the tank 2moro and have a shifty round the hoses - i used silicon vacuum hoses for the iacv, they may be getting crushed.
The stepper definately is making a cycling noise under the tank when i test it in tuneecu
i loaded new maps on for the after market (TORS) and she is running super smooth after heat up and is really crisp on a run.
thought i should do this to rule out someone previously messing with the map anyway, but still the same when i went to start this morning- starts fine then after a few secs she starts to drop revs and dies. Once she is warmed up she idles very smoothly.
will keep you guys posted
thanks again
Dell
 

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this is probably more what you are looking at under your tank... same as mine. possibly loctite would keep them in check, though that would be a bit much
Dichotomous, do your IAC Valve tubes go directly to your ICV without any other hoses attached? Mine leave the engine and got "T" stems, which are connected on each end with houses and loop around to some sort of one way valve.

I am thinking of removing all the extra tubes to try and solve a low rpm spluttering issue I am having on my 1999 Sprint.
 
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