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Discussion Starter #1 (Edited)
Hey guys,
Was out for a ride yesterday on my 2003 S4. I had 3-4 instances where I was idling, and suddenly the rpm's jumped up 3-5k!

First time was after I started the bike, and I thought it was just taking longer to warm up, revved to about 4k for ~1-2 min, then settled back down. No throttle on or anything. I did wiggle the throttle a bit to see if it was hung up or stuck, and it would only raise the rpm's higher if applied, then fall back to the abnormally high idle when released.

Another time was after I came out of the post office, and it was still warm after sitting for only ~15 min. Almost identical situation, but took ~3 min to return to normal.

Also as I arrived home, and was low speed maneuvering between cars to park, suddenly the rpm's went up to ~5500 rpms, and stuck there for over a minute, till I hit the shutoff.

I recently installed the LSL handlebar kit, which was relatively drama free. No issues with the throttle, and have got the clutch adjusted pretty well. Also recently I have had the dealer perform the recall work on the fuel fittings to the gas tank, don't know if something could be loose, or free under there. After reading up on the subject a bit here on the forum, I am guessing maybe a hose popped off the IACV, or a leak in the airbox? Just wanted to know if anyone else has experienced this before?
Any other suggestions?
 

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With the bike off, when you roll the throttle on & off, do you hear a metallick "click" from the throttle stop when the throttle closes?
 

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Discussion Starter #3
Yes I do get the click, and most of the time it runs just like normal, just once in a while jumps up a couple thousand rpm's kinda like when it is warming up. Then it settles down after a bit. Anyone know how the warmup cycle is initiated? Would not surprise me if that it the source of the problem.
 

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Sounds like the symptoms of a throttle cable that is too tight, which is caused by improper routing, improper adjustment, or too short a cable. Next time it does what you described, try moving the handlebar back and forth and see if it goes away. If you went from clipons to a bar without getting a longer cable, there could be an issue with length. The other thing could be that the bike is running too lean and needs the CO richened up. Did you recently install an aftermarket muffler?
 

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If it did this from day 1 with the LSL kit then my best guess is the throttle cable isn't optimally routed. If not, & you get the metallic click in EVERY bar position then it would most likely be something else with the fuel management.
 

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Discussion Starter #7
Thanks for the suggestions so far fellas.

So I was out working on the bike a bunch yesterday.

I got the click in every handlebar position, and I had already been very careful to route the cable in such a way that there was no tension on it. I confirmed all this as well as checking for the click in every position. Then just to be sure I popped off the tank and the airbox and watched the throttle blades click shut, and the throttle hit the idle screw through all ranges.

But I did discover this possible cause: I looked in the manual and it suggests 1-2mm play in the handle, and mine had none since I purchased it, so I loosened the adjuster a bit, and rode it around for only about 10 minutes, and no problem so far. To be fair the ride before when it did this was once it is warm, so I dunno if it is cured yet.

My other thought is possibly the idle air controller, as I was reading in the manual that it controls the idle speed. Is it capable of altering the rpm's by a couple thousand? Also under what conditions would it perform this operation? Is there a way for me to test or service my IAC? I have checked the IAC stepper motor in my van before, and improved it's idle quality.

Justice - I don't have the stock instrument cluster on the bike, as I bought it with just a Veypor, and have been collecting the cluster/mounting bracket to mount that. Should get the bracket by this weekend and get an answer for ya there. Then I will have the Veypor available if anyone wants one for track times/etc.
 

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Bad IAC's generally cause hard-starting & stalling. My money is still on the cable. If the additional cable play cured it, then be happy.
 

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A bad IAC can make the bike act like a two stroke with huge flatslides on it - near unridable in traffic.
 

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High idle

65imp,
Last summer my '01 TT600 suddenly developed a high idle (~7000) RPM. Worst of all it did it on the way to work in trafffic: not fun. I put a MODUS scanner on it at work and found that my throttle position sensor was reading in the 15% range. It should be ~0-1%. A new TPS fixed it and I've had no problems since. The IAC is only good for about 2K increase in idle.
Will is correct in saying that a bad IAC usually fails in the downward direction, seldom upward. To test the IAC influence just pinch off the air tube to the IAC and see if the idle returns to normal. Your description doesn't sound as bad as mine was but may still be the TPS. Connecting it to a scanner via the OBDII connector under the seat will give you more info. I hope this helps.
Thom
 
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