Increased vibration (numb hands!)

Hi all,

I've noticed an increased vibration on my yamaha fazer 8 (@ ~32k km) to a point where one of my mirrors is shaking a lot at highway speeds and my hands and even my right foot get numb after an hour on the highway (hands go numb in like 20 mins).
It's never been the case for this bike and mirror vibration reminds me of my gs500f days.

I had the bike checked out but the technician blamed a crack in the fairing. That probably is the cause of the mirror shaking but the crack happened 1.5 years ago and the mirror vibration is a new thing.
There's also a buzz from the front at given rpm (but only while in motion) and the mechanic thinks that's the vibrating fairing. I'll be checking that out by removing the fairing soonish (it's one big piece so it's very annoying).

I changed the chain and sprockets earlier this year but I'm not sure if this is related. I know the front sprocket may affect vibration but there was nothing special around its installation. It's torqued to spec.
I hadn't been on any long rides before that so I can't say for certain if the issue didn't exist before the new sprockets.
I also synced the throttle bodies which had only been done once before, thinking that that's definitely the issue. Things weren't very bad though. Synced them and upped the idle speed a little bit and the bike is feeling much smoother at idle.

At one point both framesliders were a little loose and it took me a while to realize their bolts are also the engine mounting bolts (been a while since I installed them). They are nice and tight now (up to manual spec) but vibration still exists. Not sure if them being loose did something else elsewhere but it may be a red herring.

I know this is a little fuzzy (I'm feeling the same way myself) but any suggestions will be appreciated. I'll be dedicating a day or two soon to taking the fairing off and eye-balling and retorquing things and I need some ideas about what to look at.

Thaaanks!

Vibration that bad sounds like a bike I had that had spun a bearing (but still ran).

What do the tires look like, how old are they and how many km on tires? Cupped and/or out of balance tires can cause a shake.

Do your engine mounting bolts have a torque sequence? I've had some bikes that did. Wheels aligned too? Thrown any wheel weights off?

I looked into your bike a little more and it seems to be a common complaint (which is heartbreaking for me, I was thinking about getting one). There doesn't seem to be a consensus on a root cause for the problem, although the engine apparently does not have a balance shaft. Long list of places where people think the vibration was caused by loose fasteners on: rear motor mounts, stuff near the windshield/dashboard, gas tank, etc. Some suggest getting heavier bar ends (I can recommend HVMP bar ends for that), thicker bars, filling your bars with things (FZ8 bars are mostly solid, however).

Big question: What RPM are you cruising at? Can you go down/up a gear?

Got new tires March last year. Around 15,000 km on them already (ugh).

There is a sequence in bolt install/removal when removing the engine but the torque sequence probably doesn't really matter. I will retorque them in that order though. Who knows.

I'm usually cruising at around 5,000. I like being near the sweet spot (6-7k) in case I need it. This bike has an annoying dip in power around 4500 so 4k is kind of out of the question.
Loose fasteners near the dash may be consistent with the crack in the front left part in the fairing. I'll be replacing that (freaking expensive) so I'll know for sure then. Just suspecting that a vibrating fairing would not be enough to upset the whole bike at speed.

Although hideously ugly, some people swear by the huge foam grips to clean up vibration before it gets to your hands.

Did you put the same size sprockets on? Changing sprocket size could push the engine into a more vibration happy range.

I have similar issue, and I'm thinking it may be front tire - it's old and one of the weights chipped off. Also, I read somewhere that not rotating it when it's winterised may result in flat spots. (15k is quite a bit for a tire, isn't it?)

I have an FZ8, and have had several Yamahas in the past (and present). It's naked so no fairings, I don't have 'unusual' vibration like you appear to have, but my bike is smooth to me, no complaints. To answer some of the questions:

First, start with the simplest things, don't jump to the expensive theories.

No comparing different bikes mechanically. Does the vibration on a harley davidson when compared to your old GS500 mean that something is wrong with the Harley? No.

Does your Fazer 8 have OEM steel bar ends (they are large compared to other bikes), or do you have plastic/aluminum aftermarket ones. That right there would explain the excess vibration in your hands.

You have a big (or small) shouty exhaust coming out the right side of the bike. On my bike the muffler is not bolted to the rearset, but the vibration still comes through and can be felt. It is the same with my R6, it's nothing to be concerned with, it's just how it is. My FZ8 came with rearset pegs with really thick rubber, probably to dampen vibration. I've switched to vortex rearsets but have a good set of boots, so it's ok.

Unless the crack in the fairing is huge and 12 inches of fairing is flapping about when you are on the highway... and even then, it's not going to cause vibration in the front end of the bike as you describe it.

Are you trying to figure out a compound problem? You mentioned that some engine mounts were loose, and other things have vibrated loose like the mirrors. have you considered that the engine mounts were loose to begin with, and that extra vibration cause other things to become loose? Check all the engine mounts, put some lock tite on everything loose and start over.

I wouldn't worry about the buzz at a specific rpm. For me it sounds more like a scratching sound, and it happens on my FZ8, my 08 R6, my 07 R6 (sold), my 04 R6 (sold), and my 03 R6 (sold). It may just be a yamaha trait, I wouldn't worry about it unless the sound is getting worse and you can actually see what is wearing out on the bike.

If your chain is too tight or too loose, it won't cause bike vibration. if the chain is loose you will hear it slapping about. No harm in checking it though.

15k on your tires? They are either close or at the end of their life. If a wheel weight came off the front wheel it would explain the vibration. Also, looking at the tires will tell you if you have a wheel problem. Are the tires smooth or chewed up ('chewed up' can be explained in detail if needed)? Also, move your hand over the front tire, does it feel like a wave pattern in the center, where some parts are lower and some higher? This is another indication the tire is at the end of it's life, and tires at the end of their life will make the bike feel strange compared to good tires.

These are some of the simple/cheap things to check before going into more expensive/complex things like the engine and suspension.

Have you installed some kind of after market bar ends?
Have you checked you stem bolt?
Have you recently installed new tires?

llaen said:

Hi all,

I've noticed an increased vibration on my yamaha fazer 8 (@ ~32k km) to a point where one of my mirrors is shaking a lot at highway speeds and my hands and even my right foot get numb after an hour on the highway (hands go numb in like 20 mins).
It's never been the case for this bike and mirror vibration reminds me of my gs500f days.

I had the bike checked out but the technician blamed a crack in the fairing. That probably is the cause of the mirror shaking but the crack happened 1.5 years ago and the mirror vibration is a new thing.
There's also a buzz from the front at given rpm (but only while in motion) and the mechanic thinks that's the vibrating fairing. I'll be checking that out by removing the fairing soonish (it's one big piece so it's very annoying).

I changed the chain and sprockets earlier this year but I'm not sure if this is related. I know the front sprocket may affect vibration but there was nothing special around its installation. It's torqued to spec.
I hadn't been on any long rides before that so I can't say for certain if the issue didn't exist before the new sprockets.
I also synced the throttle bodies which had only been done once before, thinking that that's definitely the issue. Things weren't very bad though. Synced them and upped the idle speed a little bit and the bike is feeling much smoother at idle.

At one point both framesliders were a little loose and it took me a while to realize their bolts are also the engine mounting bolts (been a while since I installed them). They are nice and tight now (up to manual spec) but vibration still exists. Not sure if them being loose did something else elsewhere but it may be a red herring.

I know this is a little fuzzy (I'm feeling the same way myself) but any suggestions will be appreciated. I'll be dedicating a day or two soon to taking the fairing off and eye-balling and retorquing things and I need some ideas about what to look at.

Thaaanks!

Click to expand...

Some great suggestions, thanks!

No aftermarket bar ends or exhaust. Which is why I'm so mystified by the change in vibration.
The front tire is not wavy right in the center but it is slightly to the left and right of it. Don't know if that's normal or not.
Might be a good idea to get new tires before the roads start to get consistently cold and wet.

I'll update this after I get a chance to give the once over.

Sounds to me like its probably a missing balance weight on one of the tires. Cracked fairing definitely wouldnt cause the bike to vibrate hard enough to shake bolts and mirrors loose unless you ride around on the highway at 200kmh.

Just a short update on this.

Turned out the problem is only really pronounced when I have a passenger which kinda points to the wheels, as most of you suggested (more weight, more vibration).
The front wheel makes a slight noise when spun (with brakes removed) which sounds like either a bearing issue (though the wheel seems pretty solid when pulled and pushed) or a balance problem. Because the sound is not constant, I'm leaning towards the latter.

Pretty sure this will go away with a new set of tires. Worst case I have to change the bearings.

Sounds like you may have it sorted/figured out, but I just wanted to add did the bike start doing this recently or has it always been this way? Some people seem to be very sensitive to vibration, and anything short of an electric motorcycle will bug them. I'll get numb hands (mainly throttle hand) on my CBR650F anywhere between 1-3hrs in, but that just seems to be par for the course on smaller 4 cylinder bikes. Also only notice vibrations between 6200-6400rpm, but it seems most 4 cylinder bikes have a spot somewhere in the rev range that does the same.

Sounds like you've got it figured out.

You need to make sure you're at least lubricating the wheel bearing when changing the tires.

Dunner said:

Sounds like you've got it figured out.

You need to make sure you're at least lubricating the wheel bearing when changing the tires.

Click to expand...

You can't lubricate/grease closed bearings