2004 Yamaha fz6 - throttle issue

[Alvito]

Hi,

I was riding a couple weeks ago and while passing a truck with the throttle pinned, the bike locked itself into the 16,000rpm range. It went full tilt for a couple seconds before I pulled the clutch back in and hit the kill engine switch.

Once parked on the shoulder, I tested the throttle and it was springing back into place. Once the bike cooled down. I restarted it and it immediately went full RPMs. I shut down the bike and had it towed home.

In April, I had a private driveway mechanic do a valve clearance adjustment, spark plugs, cam chain, oil change, and brake fluid flush. I rode the bike 2 or 3 times before the RPMs started to run away.

Google gemini thinks the throttle cable is pinched or twisted in a way which locks it into the wide open position.

It also suggests that there may be unmetered air getting into the engine.

I wasn't comfortable doing the valve clearance job. I'm debating if I should try to dig into it and see if I can reseat the throttle cable/find an obvious air leak.

Any thoughts and encouragement would be appreciated. As well as a shop near Lawrence and Victoria park that could help tow the bike and sort it out for me.

Side note: the tow operater had the kickstand down while strapping the bike down. I was not a fan of that. The kick stand feels "loose" when engageling it. Should I get a shop to check this out too?

 

[GreyGhost]

Rev limiter while in gear should not be an air leak. While a leak can increase revs in neutral, most leaks are small and dont unleash substantial hp.

I would be focusing on the throttle cables. Your second paragraph where throttle tube was springing back and bike went to redline is strange. I'd have to look at diagrams to figure that one out. Can the cables move without moving the actual throttle?

This thread seems similar:

Stuck Throttle, not cables or grip.

'07 FZ6 I know what you're thinking, yet another stuck throttle thread. Just lube the cables! I've dissembled the grip & cable housing, everything's moving freely there (well, the grip needs some TLC, 10 years of being an "outside bike", but it still turns freely with the cables...

www.600riders.com

 

[Mad Mike]

I’ve seen that happen on an FJR, it was corrosion on the rod actuating the throttle body.

Here’s what I’d do.

1. Disconnect both the cables from the throttle body and check they are a) routed correctly, and b) smooth back and forth. If they are not smooth, disassemble the throttle, make sure it’s not binding, then test each cable for smoothness. If anything is binding, don’t lube - replace.

2. With cables off, actuate the throttle body rod. It should be smooth and it should snap back forcefully. If it doesn’t, shoot some penetrating fluid (I like Zep or PB blaster over WD40). Work the shaft until it snaps back every time.

3. Check for correct routing. Sharp radius on cables can cause binding even when they test smooth.

Don’t do any of these tests when the engine is running. Once you’re certain all is smooth, then run the motor for a final test

Air leak is not going to cause a WOT condition, it might cause a slow return to idle, rough idle, and sputter or surging on acceleration - and of course engine damage over time from running lean.

 

[Alvito]

Rev limiter while in gear should not be an air leak. While a leak can increase revs in neutral, most leaks are small and dont unleash substantial hp.

I would be focusing on the throttle cables. Your second paragraph where throttle tube was springing back and bike went to redline is strange. I'd have to look at diagrams to figure that one out. Can the cables move without moving the actual throttle?

This thread seems similar:

Stuck Throttle, not cables or grip.

'07 FZ6 I know what you're thinking, yet another stuck throttle thread. Just lube the cables! I've dissembled the grip & cable housing, everything's moving freely there (well, the grip needs some TLC, 10 years of being an "outside bike", but it still turns freely with the cables...

www.600riders.com

Yeah. Throttle tube springs back. Is it possible for the throttle cable to open and get stuck open, but still allow the return cable to put the throttle tube back in place?

 

[Glenn/RZ500]

Sounds like the throttle cable is pinched/kinked. Any chance whoever did your service got the cable out of place when they were lowering the tank back in place, I had an `04 same as yours. Put the bike on the center stand, start it and turn the bars lock to lock and see if the revs increase.

 

[Alvito]

Sounds like the throttle cable is pinched/kinked. Any chance whoever did your service got the cable out of place when they were lowering the tank back in place, I had an `04 same as yours. Put the bike on the center stand, start it and turn the bars lock to lock and see if the revs increase.

When I start the bike, it automatically revs past the limiter. I really don't want to start the bike until I take things apart and see what I'm working with.

If I gather up the energy this week, I might take things off piece by piece throughout the week. If not, I'll have to do it on the weekend.

 

[Relax]

When you pull the throttle and let go do you hear the throttle plate(s) snap shut? Do you feel tension on the throttle or is it loose?

 

[GreyGhost]

When I start the bike, it automatically revs past the limiter. I really don't want to start the bike until I take things apart and see what I'm working with.

If I gather up the energy this week, I might take things off piece by piece throughout the week. If not, I'll have to do it on the weekend.

I like Mike's approach and it doesn't require starting the bike.

 

[Alvito]

When you pull the throttle and let go do you hear the throttle plate(s) snap shut? Do you feel tension on the throttle or is it loose?

I do not hear anything from the throttle plates, even with my head right by the throttle bodies as I turn and release the throttle.

I can see the throttle cables, they both seem to be functioning as they should. I don't know how much slack they should have, but there is a small amount of slack on the throttle cable. When I turn the throttle, the slack is removed and the throttle hits the metal plate that stops it from going further.

My apologies for not knowing the proper names for things.

 

[Alvito]

I like Mike's approach and it doesn't require starting the bike.

Yeah. I think I have to break up the job into small chunks and try to get through it during the work week. By the time I get to the weekend, I'm too tired to do anything. Haha.

I will try to dig into it soon and see what I find and report back.

Thank you all for the support. I owe all of you a coffee. From Tim's... Not Starbucks... I ain't made of money.

 

[GreyGhost]

I do not hear anything from the throttle plates, even with my head right by the throttle bodies as I turn and release the throttle.

I can see the throttle cables, they both seem to be functioning as they should. I don't know how much slack they should have, but there is a small amount of slack on the throttle cable. When I turn the throttle, the slack is removed and the throttle hits the metal plate that stops it from going further.

My apologies for not knowing the proper names for things.

If you can get an angle with your phone, take a video of throttle body end of cables as you cycle the throttle. You can make a youtube account to post the video. I suspect that is the problem area.

 

[Relax]

If it were my bike I’d remove the tank and airbox/filter so I could visually confirm that the throttle bodies look ok and operate properly. Then you can do all messing around with the cables. For all we know there could be an air leak from the throttle body boots being loose or dislodged.

 

[Relax]

 

[Glenn/RZ500]

I seem to recall there was a TSB or recall for that, totally forgot about it.

 

[Alvito]

If you can get an angle with your phone, take a video of throttle body end of cables as you cycle the throttle. You can make a youtube account to post the video. I suspect that is the problem area.

I will do that today and post the video. I will also start to take off the plastics and see how far I can get with maybe taking off the tank too.

If never done it before, but I have the shop manual, so I'll follow those instructions.

 

[Alvito]

If it were my bike I’d remove the tank and airbox/filter so I could visually confirm that the throttle bodies look ok and operate properly. Then you can do all messing around with the cables. For all we know there could be an air leak from the throttle body boots being loose or dislodged.

So it took all of just 30 minutes to get the plastics, gas tank and the top of the airbox off. It started to drizzle so I had to put the bike back into hiding.

I still need to remove the airbox and test the sensor. Those Allen screws holding the airbox down are in a pain in the ass spot. Its too dark in my shed to try to take them out.









Youtube Video:

 

[Brian P]

Shut isn't shut all the way. In the rest (idling) position, the gap between the throttle and the inside of the throttle body should be next to nothing, and it's way too much. See 38 - 45ish and 58 seconds into the video.

The next challenge is to find out why the throttles aren't closing all the way against the idle stop screw (which you haven't found yet).

The wobbliness of your footpegs is because they're rubber-mounted. I can see the rubber bushings. (Vibration control)

 

[Alvito]

Shut isn't shut all the way. In the rest (idling) position, the gap between the throttle and the inside of the throttle body should be next to nothing, and it's way too much. See 38 - 45ish and 58 seconds into the video.

The next challenge is to find out why the throttles aren't closing all the way against the idle stop screw (which you haven't found yet).

The wobbliness of your footpegs is because they're rubber-mounted. I can see the rubber bushings. (Vibration control)

Okay. Airbox will be coming off next and I'll take a look at the idle stop screw, that would be on the wheel with the throttle cables, yeah?