Scary throttle issue...help

Nimbus

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I rode to work today in a periodic and ultimately relatively dense fog. Upon pulling into our driveway and slowing for a speed bump with the clutch in, the revs dropped very low (on the verge of stalling). The bike stumbled and I pulled into a parking spot. The idle dropped very low again threatening a stall. I revved it up a bit and the revs hung at perhaps 1500rpms before dropping to the low rev situation again. I shut it off, and it started, but back at low revs.

I assumed that perhaps the fog had somehow screwed up a possibly leaky spark plug coil or a TPS/APS/YCC-T sensor and that it would dry out by the end of the day. So, I started up after work and it ran at about 1800 rpms (cold?) and settled down to about 1300 or so. Oddly, it wouldn't allow me to switch throttle modes. Pulling through the parking lot, I realized that when I rolled off the throttle, it remained hung (did not accelerate). It would rev like usual, but had odd, inconsistent throttle-return response. I shut it off (kill switch/key) and then re-started. It did this for a few miles until I pulled off and restarted it again. All seemed well at that point. I was able to switch modes consistently. But 5 or so miles down the road, there was again an issue (mostly I noticed due to not being allowed to switch modes) which disappeared after restart. After that, it seemed fine until I went WOT and it kept 7K as I shifted. Subsequently, I rode it for about 30 minutes without any issue at all. I'm not sure what's going on.

I'm baffled and pissed. Bike is out of warranty and WTF is with a fly by wire system that won't shut off when you tell it to. What about redundancy? Anybody have ideas? Suggestions?
 

snakebitten

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I've read nearly every post for more than a couple of years. Your description is NOT anything I've ever heard before. Gotta be a very unusual issue. But as well as you described it, some of these motor heads around here are likely to have a good idea of how to chase this down.

Throttle bodies not in sync with the sensor our cables are connected with?
 

Karson

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Stuck throttle cables that could use some attention? Start with the obvious first. The cold rpm transition is normal and eventually would've settled down to around 1100. Thinking out loud...makes sense if it detected throttle input where it shouldn't and not being able to switch at one point
 

Firefight911

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First off, what are you "pissed" about? Relax, lose the emotion. I would reference Apollo 13 on this one and let's work the problem.

Look at the throttle tube to see if there is any debris in it that is hanging up the return. Check the throttle cables for sticking. Check the wire/cable routing for kinks and/or hang ups. Throttle sync check. What was the temp outside during this? What was the bike coolant temp at issue occurrence? Do you have the jumper mod? Check the throttle position sensor for drift out of spec.

People, let's work the problem.
 

bloodline

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Mine did this, once.

http://www.yamahasupertenere.com/index.php?topic=5692
 

snakebitten

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That was a very short thread. I didn't recall it. Sorry.

So you never said what happened after that Bloodline. Been normal since?
 

rotortech71

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Not switching between T and S is obvious, since it was only detecting an open throttle and not allowing a switch. Done any maintenance lately? New grips, heated grip install, or work under the tank and around the throttle bodies?
 

Nimbus

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rotortech71 said:
Not switching between T and S is obvious, since it was only detecting an open throttle and not allowing a switch. Done any maintenance lately? New grips, heated grip install, or work under the tank and around the throttle bodies?
This is exactly what I thought also, that the T and S issue is a major clue. I've done nothing recently but ride. Heated grips were done like 10K ago and I did the sync when I last did my spark plugs several thousand miles ago. I did go out to the garage 45 minutes after I got home and started the bike again. It started up like normal, idled perfectly, and switched modes. I basically did the heat it up to check the oil routine and shut it off.

Firefight911 said:
First off, what are you "pissed" about? Relax, lose the emotion. I would reference Apollo 13 on this one and let's work the problem.

Look at the throttle tube to see if there is any debris in it that is hanging up the return. Check the throttle cables for sticking. Check the wire/cable routing for kinks and/or hang ups. Throttle sync check. What was the temp outside during this? What was the bike coolant temp at issue occurrence? Do you have the jumper mod? Check the throttle position sensor for drift out of spec.

People, let's work the problem.
I wasn't really pissed as much as disappointed/bummed/irritated. Face it, it's scary when the bike doesn't respond when you let off the throttle. I'm certainly open to working the problem. Sadly, I don't have time over the course of the next week to do anything but simple stuff. If it is, as I hope, a one off occurrence, I'll not have much to really test. Once the issue resolved on the way home, I rode the bike HARD and it performed without any flaw. It wouldn't appear to be a throttle cable sticking issue and there are no clear hang ups. Outside temp this AM was 36 (a cold fog) and afternoon temp was low 50s. Coolant was up to temp and bike was fully warm after the 20 minute ride to work. No jumper mod, but the bike was flashed this summer (absolutely no problems since).

Karson said:
Stuck throttle cables that could use some attention? Start with the obvious first. The cold rpm transition is normal and eventually would've settled down to around 1100. Thinking out loud...makes sense if it detected throttle input where it shouldn't and not being able to switch at one point
The cold RPM transition was not normal and when it started to settle to 1100, it went back up.
OldRider said:
First thing I would do is tighten both battery cables. A lot of problems come from loose cables.

I can check the battery cables if it occurs again.
 

Nimbus

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bloodline said:
Your situation sounds similar to mine in as much as I restarted the bike at one point and it went totally back to normal. Then it acted up again, but with more subtlety each time.

And for the record, you guys are awesome! Thanks to everyone for the support. ::015:: I told my wife about the issue and she was impressed about the forum support.
 

GrahamD

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Firefight911 said:
First off, what are you "pissed" about? Relax, lose the emotion. I would reference Apollo 13 on this one and let's work the problem.
+1. You're on the ground with plenty of oxygen left. No reason to panic.

https://soundcloud.com/thisisparker/apollo-13-houston-we-have-a-problem-nasa

I would look for something not allowing the throttle to return properly OR something that is making the ECU think it isn't as a first case. Loose electrical connectors, connections would be a place to start.
 

Nimbus

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Fired up the bike this AM and...all was well. Not sure if my bikes just protest in cold miserable weather or what? My first bike would ice the carbs, the SV would lose the front cylinder in the rain. Anyway, I'm hoping for a Bloodline esque fluke. Fingers crossed.
 

viewdvb

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Dealing with the suggestions one at a time:
Sticky cables? Yes, they would prevent the engine revs slowing appropriately and could prevent the mode switch if the ECU detected that the throttles were not fully shut but that's easy enough to check. No mode switch? Pull in the clutch or select neutral and, if the engine seems to be running at normal tickover but the mode won't change the cables are not the problem. And sticky cables could not cause the engine to run at near stalling revs.
Wet/dirty plugs? Definitely could cause erratic running but they would normally clear when the engine has run for a while before which you would expect to experience hard starting. Did you? Besides, spark plugs are so good these days that I would never expect to see one that I would call "dirty" though "wet" definitely does happen when the dreaded hard starting syndrome due to flooding happens.
ECU problems? Maybe, especially as it has been meddled with, but dirty/corroded connectors are more likely. It would do no harm to disconnect everything related and spray with switch cleaner before reassembly.
Throttle position sensor loose or out of adjustment? Good candidate though, if it is not loose, how could it become maladjusted? Nevertheless, the TPS has a lot of effect on slow running and a loose one could explain the changing symptoms.
Good news: problems that occur intermittently aren't too likely to be major failures which NEVER just heal up so your ECU is probably OK.
Good luck.
 

Ironhand

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I had a similiar sticky throttle issue late last summer. I had been riding all day in the rain with heated grips on. After I got it home, I found where a small dribble of grip glue had run between the throttle tube and handlebar. Why it waited several thousand miles to act up, I have no idea. As far as I could tell, the tiniest bit of expansion caused by the tube and/or bar expanding when hot was just eneough to cause that bit of glue to drag on that bar. I cleaned it off and have not had an issue since.
 

~TABASCO~

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Maybe a few of these things have been mentioned but Ill throw out a few things........

- dirt , crap under the plastic throttle
- dirt, rock stuck behind the black plastic cover next to the motor linkage on the throttle bodies.
- remove the air box, look to see that both butterflies are still in factory location and move smoothly and 'normal'... You can also start the bike to make sure they are 'normal' when running.


When I bought my bike the RPM where going high then dropping down to 600-800 Rpm and then about to die,,, then jumping all back up and such on a brand new bike.... I did the throttle body sync and adjusted the CO and that took care of my issue... You might want to check the air screws on your throttle bodies just to make sure they are both in the correct position... I know of only one customer that has confirmed his air screw backed out so far it almost fell out... The reason he was looking is because his bike ran like total crap... After he re synced the TB's it ran great...

Just a few thoughts that quickly came to mind....
 

WRW9751

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I to have had a throttle problem. As I was just about to go on a longer ride. Panicked, Started dissembling stuff only to find the handlebar was horribly corroded! Cleaned it sanded the rust and gunk away. I'm one of the few who likes the bend of the bars and would like to keep them. That said another inmate I know just changed his for a pair of Pro Taper's Aluminum. Vibration diminished and you wouldn't have to worry about rust under the throttle tube.
 

Nimbus

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When I get a chance I'm going to go through each of these suggestions and then let you all know.

As far as hard starting, the bike started normally both times the issue occurred and would start just fine even as the issue was occurring (when I cycled the key/kill switch). I would think if it was a dirt issue, then it wouldn't just go suddenly away, but who knows? Maybe a small amount of wet dirt would make it act up until it dried out? Anyway ,the bike sat in a light dusting of snow so got damp today and I'll see what happens when I ride it home this evening.
 
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