Vibrations in handlebars at speed, goes away if I pull the clutch and let go throttle

[Frankgg]

Hello everyone!

I have a rather weird annoyance with my 2005 FZ6.

Over 30mph, I get some small but fast vibrations in the handlebars. At first I thought my front tire needed to be balanced, but now I believe it is engine related, due to the fact that:

1. I get up to 60 mph and let off the throttle, engine still at higher than idle RPM, vibrations continues

2. I get up to 60 mph and let off the throttle AND pull in the clutch, engine goes down to idle RPM, vibrations STOP!


Does the FZ6 have engine mounts that can go bad or something?


(Background on my bike: I purchased it used, previous owner had put and after market exhaust on and a PC commander, though I've re-checked the PC Commander settings and its on the correct settings - Stock bike + Scorpion Exhaust)

 

[FZ1inNH]

One simple thing to check first is all the nuts and bolts in the front end. Do you have a torque wrench? If so, start with the handlebars. The proper way to torque is to back the nut or bolt out to a loose state, then tighten to the torque specs.

Do this for the handlebars and bar-ends then also do all the bolts on the triples that clamp the fork. Check the clutch and brake brackets as well. Check the steering head bearings... put it on the center stand, raise the front and grab the forks. Pull and push them back and forth and if there is ANY play, you will need to adjust accordingly but we'd recommend dropping the stem and inspecting the bearings. If they are OK, repack with grease and follow the procedure to tighten them to spec.

Last, torque all the engine mount bolts, especially the ones the frame sliders (assuming you have them) are mounted to.

Take it out for testing. See if you've resolved the issue.

 

[Erci]

While it's a very good idea to check torque on all bolts, I bet the vibration you're describing is perfectly normal. It has nothing to do with speed.. it's the engine RPM. This bike puts out most vibration at about 5k rpm. Try to squeeze your heels in as you ride to see what I mean.. at 5k, it'll vibrate a LOT.
This is normal.. if it bothers you, try to stay out of that RPM range

 

[FZ1inNH]

My '05 and '08 never vibrated through the bars and into my hands. Hmmm.....

 

[lonesoldier84]

if you drop the bike into neutral and turn the engine off....the vibrations stop completely!!!

 

[CheapBastard]

Hey,
I hope you've solved the vibe problem, but if not, I have another suggestion (garnered from general engine work, not on the FZ6 in particular, as mine has run perfectly to date).

How does your engine run at a standstill? Can you re-create the "unusual" vibes then? If yes, that will mean something is definitely up with the motor (keep in mind it doesn't rule out front end problems though).

If you're pretty sure it's engine related and you've checked the mounts etc., the next place I would look is to the fuel injection and plugs. If the throttle bodies are out of sync or the Power Commander (which I'm not really familiar with) maps and the injectors are not providing optimum fuel mixtures to every cylinder, your engine could be running a bit unbalanced at times. You could also have a fouled plug or other spark issue on a cylinder or two: that could cause weird vibes if those cylinders are missing regularly.

None of the engine scenarios is particularly likely, I imagine, but you never know if the engine was run on the "wrong" injection settings or bad fuel long enough to foul something or clog an injector: it might not hurt to pull the plugs and take a look at them, in any case, if you're being driven nuts by the vibes.

Hope you get it sorted!

 

[tuningfork]

I agree, I'd sync the TBs and have the bike tune checked on a dyno. I honestly would not trust those pre-made maps, there are a lot of variations in bikes, fuel quality, etc...enough I would want to confirm the map is right for YOUR bike.

 

[Erci]

Another suggestion.. if you can find someone with FZ6 and swap for a few miles to see if vibration is there on someone else's bike, it may save you a lot of headache / money
(I still think you're experiencing normal 600cc vibration)

 

[SovietRobot]

The inline 4 engines like in our bikes are prone to a resonant vibration, usually between 4-6k RPM's, which is normal.

Try syncing your throttlebodies, that should help.