Revs not lowering when warm - Suzuki GSX-R Motorcycle Forums Gixxer.com

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post #1 of 14 (permalink) Old 03-25-2019, 12:02 PM Thread Starter
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Question Revs not lowering when warm

Hello everyone!

Ive got a problem, I could not find in the forum...

The bike runs great, no herky-jerky TPS, accelerates up until 16.000rpm without a flaw, no stuttering, no FI, -C00!
But when it has about 80-90 degrees (Celsius), the rpm stops lowering, correctly.
Pulling the clutch at 4500 leaves you with 4000rpm and I must break it down. It stays there then, until I accelerate again.
No difference if driving or in neutral.
That is really annoying and also dangerous, if you cannot lower the speed without breaking!
If you are cornering, you feel the bike is "pushing" you through.
Or like the gas bowden cable hangs, which definitely doesnt.

Idle TPS setup (dealer mode) seems right, cold and warm. The behaviour just starts above ~80.

Maybe someone can help me how to figure out what this can be.
Thanks!
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post #2 of 14 (permalink) Old 03-25-2019, 12:30 PM
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Re: Revs not lowering when warm

It almost sounds like your throttle cable isn't retracting easily when you come off the throttle. Have you disassembled and lubed the ever living shit out of her? Im not an expert they will post later haha just trying to go over some issues ive found small fixes for.
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post #3 of 14 (permalink) Old 03-25-2019, 06:50 PM Thread Starter
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Re: Revs not lowering when warm

Yes, that was the first thing I checked and WD40-ing extensive.
Ive even bought another throttle in advance, to determine that it was really temperature related.
The bowdenwire works smooth.
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post #4 of 14 (permalink) Old 03-25-2019, 07:57 PM
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Re: Revs not lowering when warm

First, double check your cable routing.

Second, do NOT use WD40 as lube. It isn't.

Third, it sounds like your idle screw maybe be wonky.

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post #5 of 14 (permalink) Old 03-26-2019, 05:57 AM
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Re: Revs not lowering when warm

If the throttle snaps shut, or if you can't manually close it, say by turning the pulley it attaches to (which should be accessible through the tank and frame) and have the engine speed go back to proper idle, then it's probably not the throttle (but check to make sure!). If that is the case, try disconnecting the IAPS sensor (the one mounted on the airbox, where all the vacuum hoses go to; see the services manual). The engine should operate more or less normally, but don't ride around like that more than necessary. (It'd be best if you disconnect the sensor with the engine already warmed up to the point where the issue has manifested.) If the issue goes away, check your vacuum hoses for rips, cracks, or other defects that might cause leaks.

By the way, the engine speed doesn't go down to idle if you pull the clutch or better yet, switch to neutral, does it?
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post #6 of 14 (permalink) Old 03-29-2019, 07:44 AM Thread Starter
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Re: Revs not lowering when warm

As I wrote, this behaviour does not have anything in common with the throttle, cable or routing!
The spring pulls the wire always back to the initial position. It hits the suspension point of the disc, where the bowden cable is attached to.

Also there is nothing wrong with the idle screw. The idle rpm is great, so is the rpm when cold.

You can let it run on 1150rpm until it reaches 80. Does not matter if neutral or pulled clutch.
If you now raise the rpm, f.e. to 5000, it will stay on 4000 after releasing the throttle.
It seems that it is temperature depended and the rpm will stay higher on higher temperature.

The only way to lower the rpm, is to clutch in with breaks on, careful.

Same thing happens while driving. You will feel, that the engine break is missing. Pulling the clutch lets the rpm stay where it was.


My uneducated guess is, that one of the sensors (TPS, S-TPS, IATS, IAPS, whatever) has a cold soldering or the resistor is done.
Ill try to check your suggestion @dpapavas and disconnect the sensor to see what happens
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post #7 of 14 (permalink) Old 04-01-2019, 04:16 AM
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Re: Revs not lowering when warm

Another explanation might be a dragging clutch. Thermal expansion or whatnot might be causing the clutch to stay partially engaged even when the lever is released, dragging the motor along with it. If the problem goes away when in neutral, make sure your clutch is properly adjusted. (Although, since you report reduced engine braking, this explanation is not very likely).
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post #8 of 14 (permalink) Old 04-24-2019, 11:37 AM
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Re: Revs not lowering when warm

I had a similar issue on my 07 GSX-R750. It wound up being the servo motor on the Throttle Body assembly. The mechanic I took my bike to had the same bike so he took the TB assembly off his bike and put it on my bike to confirm. You can't buy the servo motor seperately though, so I picked up a used TB assembly (complete with servo motor) off ebay and it's been fine since.
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post #9 of 14 (permalink) Old 04-24-2019, 11:56 AM
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Re: Revs not lowering when warm

I had a problem like that on 750k6 and it was secondary throttle position sensor (STPS) which has gone mad
If You take off the airbox and look at butterflies inside secondary throtlles they open (like on cold engine in fast idle mode) and do not close... sometimes touching/pressing the STPS sensor makes the idle okay for a while (or it did on mine) as the sensor might be fucked/unpredictable...
I could not find cheap second hand STPS that would work and bought used throttles with all sensors on.
It may not be the case but worth checking...

Currently on GSXR-1000K4
used to have GSX-R750Y and GSX-R750K6(among other bikes).
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post #10 of 14 (permalink) Old 04-24-2019, 05:07 PM
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Re: Revs not lowering when warm

Just out of interest, is approx. 1500 rpm the right idle for a k7? Seems quite high to me, it's what mine seems to
idle at. Bike runs fine, I can see in the manual I think it is down as 1250 idle?
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post #11 of 14 (permalink) Old 04-24-2019, 06:19 PM
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I would think TPS or lower your idle speed when your bike running and warm. My bike before would also do the same thing where if you came to a stop, the idle hangs pretty high then would eventually drop down to normal after a couple seconds. I just adjusted the idle and it stopped doing it. Also, even though the TPS is showing -C00, that could be the issue meaning you have to find a sweet spot. I put my bike in dealer mode with the bike already warm and running at operating temperature and it was showing -C00, so I had to go barely higher since the thing is sensitive. If it stays at 4000, its feeding too much gas? Someone correct me.


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Last edited by JamesIsMe; 04-24-2019 at 07:39 PM.
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post #12 of 14 (permalink) Old 04-30-2019, 04:59 AM Thread Starter
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Re: Revs not lowering when warm

My tank was located at my painter, so I could not go on testing further...
Tomorrow Ill go on a racetrack in Croatia, where I want to test your Ideas. Thanks!

Hope I will have some results then
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post #13 of 14 (permalink) Old 05-06-2019, 01:45 PM Thread Starter
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Re: Revs not lowering when warm

Guys,

it was simpler then I thought!
The (warm) idle screw was screwed
It was kind of loose and seemed to change, when warm and on vibrations. "Glued" it with lock-tight an now its fine!
I will check if the screw thread is done and if I can change/repair it, right.

Sometimes it feels like it still hangs a half second on 3.500rpm when lowering, but instead of the behaviour before, it then goes down.
The bike feels so much better in corners! Love it
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post #14 of 14 (permalink) Old 05-06-2019, 10:07 PM
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Lower the idle screw at operating temp to 1200
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