Do throttles stick open?

[cswett]

Had a scary moment on my first ride over the San Francisco-Oakland Bay Bridge today. Was accelerating to about 50 mph to slide into a gap in an adjoining lane during the morning commute, and the bike did not slow down when I let off on the throttle. I pulled in the clutch, the engine roared for less than a second, and then it went back to its normal RPM.
It acted exactly like I had not rolled off the throttle, though I'm sure I did.
I finished my chores in San Francisco and then rode back to Sacramento, about 100 more miles, with no recurring problems.
Bike is a 2004, no Throttlemeister or other grip accessory, just about to turn 10,000 miles. Heated grips were turned to the low setting, if that means anything.
Any thoughts?

[challey]

While I haven't heard of this happening to the R bikes, it certainly is possible for the throttle to be held open due to mechanical problems (the TBs or the throttle cables sticking). It may also be possible for an electronic issue to be the cause (the ECU or TPS) - hopefully someone else with more than my rudimentary diagnostic skills can comment on that.

I'd think the most likely culprit is mechanical. It's relatively easy to check to check to see if each TB butterfly and associated linkage is working properly by simply loosening the tube from the air box to the TB manifold, sliding it back and visualizing the working of each TB as you open and close the throttle. It's possible that some grunge has built up in the interior, which you should be able to see - and clean out if that's the problem. You can also see if any grease or girt has built up on the outside of the actuating mechanism that could cause things to stick - carb cleaner spray or even WD-40 would work. If the throttle cables are binding, you'll have a tougher time fixing things. I'd think that the most likely culprit in this case would be the assembly under the battery tray that takes the throttle cable from the twist grip and the one from the fast idle and links them to the individual cables for each TB. It could be that some grease/grit/debris has gotten into that assembly. This can probably be cleaned out relatively easily - the problem is getting access to it since it's under the battery tray. It could also be that throttle cables themselves are binding somewhere, though I'd think this is unlikely at only 10,000 miles since the cables run through a nylon or teflon core in their sheathing.

I'm sure someone else will chime in to correct anything I've written or omitted but I'd start with checking the simple things.

Charlie

[rdsmith3]

Was it the rubber grip rubbing against the bar end? Did you have the heated grips on?

The simplest cure for rubbing rubber is to put a washer or two in the bar end so that there is space between the rubber grip and the end.

[cswett]

So the problem of the throttle staying open (first reported in september) never reappeared until today. I was riding on the freeway to work and when I rolled off the throttle at about 4,500 rpm to upshift, bike didn't slow down and the engine roared when I pulled in the clutch. Then it dropped to normal RPMs and didn't happen again.
But tonight riding home, it got progressively worse until at one point, I was upshifting at 4,500, rolled off the throttle and pulled in the clutch and the rpms rose to more than 6,000 before dropping back off.
I assure you that is an uncomfortable feeling. Don't want to ride the bike again until I get this taken care of.
I didn't try to fix it after the first occurrence a few months ago because I wasn't sure that I had fully closed the throttle, and the problem didn't reappear. But tonight, I was sure.

Has anyone had this happen? Any obvious explanation? I am a mechanical no-nothing but sticking butterfly valves don't seem to make sense since the rpms appeared to rise, after I rolled off the throttle (unless that's a function of no load on the engine because I pulled in the clutch).
If it's just a matter of a sticking butterfly valve, I'm willing to tackle that. But how would you diagnose that? Take off the air intake tube, rev it up and wait to see if they don't close when you let off the throttle? Or should I take it out for a ride and wait for this to recur, then come back to my garage and do the rev test?

Thanks in advance

[rdsmith3]

Start simple. As I asked before, are you sure it is not the rubber grip sticking against the bar end? I have had that happen, and others have reported it, too.

[cswett]

Don't think that would be it because the engine continues to rev even after I have manually rolled the throttle back to the closed position. Wouldn't that eliminate a sticky grip as a culprit?

[owldaddy]

Heated grips were turned to the low setting, if that means anything.
Any thoughts?

Has it happened when the grip heaters were off? Sometimes the grips expand enough when heated, that the end of the throttle will touch the bar end. Adjusting the bar end a little looser should help if that is it.

[jcridge]

Like most here, keep it simple.

1. When did you first notice it?
2. Did you do anything to the bike before you noticed this condition?
3. Are you sure?
4. Simple inspection of the throttle cable, starting with the T/B end seated in the bracket and working your way back to the high idle switch on the left grip. Is there allot of play in the cable end? enough so that it can hang up off the seat at times? 10K miles on an 04, lubing the cable might be in order...
5. Wire ties too tight? This can usually be checked by turning the bars lock to lock while at idle.
6. If the cable is free and seated correctly, it is possible (unlikely though) that you have gunked up throttle plates. This condition usually presents itself when the engine is cold, when warm the plates tend not to stick as bad.

John

[Boxer]

From what you have said, it sounds like the cable pulleys inside the cable junction box have become gunked up with oil and dirt maybe and are sticking inside that box. You will have to disconnect the high idle cable and the left TB cable to pull the box out from the right side. It sits right under the battery box and slides into a metal support that is actually welded to the bottom of the metal battery holder. Its a tedious job but can be done with some care. Once that box is out you should clean it good and reinstall without grease or oil of any kind.

I can't say for certain, of course, that this is your problem, but it sure sounds like it. You can check it with the engine not running, since its just a mechanical connection. Roll on the throttle slowly and let go to see if its sticking that way.

[cswett]

Thanks all -- I'll check these suggestions out -
To answer JC ridge's questions.
1) First noticed it about two months ago, but didn't recur until about a week ago. In When I rolled off the throttle and pulled in the clutch to shift, the engine would kind of roar like I was doing a power shift, but I wrote that off to perhaps not being coordinated in my clutch/throttle control. Then last night it got much worse and I knew it was the bike and not me. I started to notice it last night about 1 mile into a 6-mile trip home, and by about mile 5 the revs would stay high for a second or two after I closed the throttle. At one point I did not think the revs would ever drop, so I hit the kill switch, then immediately turned it back on and the bike resumed revving, then the revs dropped to idle. Heated grips were not on.
2) I did nothing to the bike before this happened. Am not a tinkerer or wrencher.
3) I'm sure.
5) Wire ties have all been redone by a mechanic more than a year ago.
Again, thanks for all your suggestions.

[NoRRmad]

It certainly sounds like something's sticking. If it were just one of the lower throttle cables or one sticking butterfly valve, there would be increased vibration as the engine settles down. So, it's probably the upper throttle cable or the junction box. There's temptation to lube your way out of something like this, but remember these cables are teflon-lined and lube just attracts dirt. If a good cleaning of the affected areas doesn't fix it...replace.

Good luck!

[cswett]

More info - just went out to start the bike (with the high-idle on) and it roared to life at 6,000 rpm and my hand off the thottle. Ugh.
I hit the kill switch, shut everything down and then started twisting the throttle. It twists freely with no resistance, like there is no spring loading.
Does that suggest anything new?
Thanks again

[Boxer]

It twists freely with no resistance, like there is no spring loading

The cable has come loose either at the grip or at the junction box. It may even be broken where it is attached to the barrell end. Those barrell ends (not sure if I'm calling it the right name) will bind and with constant twisting, the cable breaks right there.

To replace any of the cables you have to take oput the junction box anyway. Sounds like you need some cable replacements.

[Flatpick]

As of today I've had the same problem with my 2004 Rockster. Moved the bike from the garage to the walkway in front of my house(about 20 feet). Had the fast idle lever up, giving it light throttle and working the clutch to move it up the walk. Clutch was pulled in, hand on throttle, bike was idling at 1200rpm. Without changing anything, it revved way up.(Didn't look at tach, but sounded like WOT) I immediately turned the key off. Tried it a couple hours later and it stayed at 2000rpm. Had the bike a year and this is the first time this has happened. Probably will trailer it to dealer. Can't trust it like this.

[NoRRmad]

Walking alongside, it's possible you brushed the lower end of the throttle cable and knocked it out of the adjustment fixture. That adds about a quarter-inch of throttle cable pull, which would increase revs. Check that both cables are fully seated.

[AndyRR]

So, what's going on at the throttle bodies? You don't have to remove any covers. No tools. They are right there. You can operate each side independantly by hand (just keep the cable in it's slot when you release).



If they seem smooth and both go to a fully closed position, you have a cable problem. You should be able to feel / hear the throttles come to a stop in the fully closed position. When fully closed, there should be a little bit of slack on the cable.

If this is outside your skill set, any bike shop should be able to handle this.

[Flatpick]

Know this has been awhile, but I discovered what probably was the culprit to the throttle sticking, engine revving problem. When inspecting the cables wile back, I noticed a vacuum line (tubing) had came loose from its bracket. Traced the tube and found it was rubbing against the throttle cable cam and stop. (Right side). Believe that sometimes it would rest between the throttle cam and its stop. Since relocating the tubing, there has been no hint of a problem with the throttle. Thought I'd share this in case someone is having throttle issues. Seems to have cured it.

https://skydrive.live.com/?cid=ae455df0 ... 6912%21107

[Dr. Strangelove]

that's pretty interesting...I am around those tubes often

But, what about cswett?

[cswett]

Turned out to be the throttle cable up near the twist grip -= was frayed and hanging by a thread. Got that replaced and life has been good. BTW, my mechanic diagnosed it over the phone -= asked me if it felt "crunchy" when I twisted the throttle (with the bike off, of course) and, indeed, it did.

[Dr. Strangelove]

ah-ha
thanks

a crunchy feel to the throttle; I suppose as if a frayed cable were binding.

good info