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Discussion Starter #1
The fast idle circuit has stopped working on my K5 650 (116,000km) and I would like some help from people knowledge about fuel injection.
The Secondary Throttle Valves turn easily by hand, but from the open position only do a quick stutter and stay open with the ignition first turned on and do not do the full open/close sweep.
I have tried to follow the manual (for a K4 which should be identical) and disconnected the STVA coupler (STV valve fully open) and measured the TP output voltage (R and b/br) wires at 4.92V.
The manual says the TP voltage should be 1.21v for this test and the fast idle adjusting screw should be used to bring the TP voltage to spec. I must admit that I could not identify the fast idle adjusting screw from my fuzzy workshop manual picture but wonder if the large range from 4.92V to 1.21 could be reached using this adjustment screw.

While the STVA coupler was disconnected I measured the STP sensor voltage at 5.2V with the valves open and this exceeded the manual's minimum value of 4.8V as required.

With everything connected but the STValves fully closed, turning on the ignition makes the valves open fully so while the STVA operates to this extent do I still suspect a malfunctioning STVA.

The bike is running perfectly otherwise with hot idle set at 1300rpm so I could just ignore the problem by manually keeping the revs up on cold start but I would prefer to fix the problem.
 

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Some additional info that I remembered reading a while back, https://www.vstrom.info/Smf/index.php/topic,16728.new.html#new, (post #2) "on p5-31 is the following: If the TP sensor output voltage is out of specification, turn the fast idle adjusting screw and adjust the output voltage to specification. TP sensor output voltage: 1.21 V (Red - B/Br). Red - B/Br is the input side. It will always read 4.5-5.5V. The output side is P/W - B/Br as shown on pages 4-30 and 9-50"
 

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Discussion Starter #4
Thanks Gert for the information. Suzuki make it hard for us ignorant home mechanics as the manual at 5/31 dealing with adjusting the STVA wrongly shows checking the red/b-br wires for the output voltage so no wonder I was confused.
 
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FWIW , on my 06 my cold idle was never right from new. After years I found an adjustment screw by the bottom of throttle cables that needed a half turn. You can adjust it without removing anything with a right angle screwdriver ,though it is hard to see, while lying down on the left side looking up towards the front throttle body. I am sure it is noted somewhere in the factory manual.
 

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Discussion Starter #6
Glad to report a new TPS fixed the STVA problem.
 

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Thanks for the link, Gert. Interesting.
I'd like to know which one, too. I've read it's most often the lower one. It was on my '07.
 

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Discussion Starter #9
The TPS replaced is no 12 on the cheapcyclespart exploded parts list, part no 13550-13D60.
Interestingly the part from my Australian Suzuki dealer was $A99 somewhat cheaper than from the US sites and that is a miracle as Australian dealer sourced parts are generally way more expensive than US.
The sensor (no 7) above the TPS is called the STP sensor which checked out OK and was not replaced.
 
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Thanx for your reply. I know from my own experience, on my K5 and K6 Wee, that if the idling is set too low (sub 1,100 prm), it would simulate a TPS like failure on pull away when the engine was cold. The bike simply cut out, while attempting to pull away from stand still. Needless to say, it caught me by surprise the first time it happened.
Anyway, I'll pass the info on and see whether it is of any help on the other site.
 
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