Extreme engine buzz from new alternator rotor?

[t3rmin]

I just installed a new (used) rotor/flywheel after I chipped a magnet on my old one (stupid mistake...). The new one had what looked like quite a few balancing holes drilled on the outside radius opposite a deposit (on the inside radius) of what looked like excess epoxy (or whatever they used to hold the magnets in place) which had apparently pooled there during assembly. It's not enough that it's rubbing the stator, but it's noticeable.

Now that the bike is back together everything is working fine except there's a very prominent harsh buzz/vibration at 5k RPM and above. I'm familiar with the usual amount of GS 5k engine buzz, but this is MUCH stronger. I'm worried the bike is going to shake itself to pieces and/or mess up bearings or something in the motor.

So it would seem, despite the obvious attempt at removing material to balance, this rotor is not balanced. Is that a reasonable explanation? Has anyone ever encountered this before?

I can find another rotor fairly cheaply/easily on eBay, but I'm a little concerned about being able to pull that bolt out after I installed it with red loctite (per the manual)...

[Tarbash 27]

something might be out of place or it might not be on their tight.

[t3rmin]

Ya know, I was looking at eBay at rotors and I see lots of them have that row of balancing holes drilled in the outside. That must be fairly normal? My old one didn't have that...

Perhaps I should just try removing it and re-installing? Maybe I didn't get it on tight, as you said. I did bang on the center hub with a rubber mallet to seat it, then torqued it down good.

[Tarbash 27]

yes mine has those balancing holes, I ended up changing my rotor too because my starter clutch cracked, I just changed the whole thing. It was a pain to get it off, I ended up using my uncles torch and beating it off. The one I put on took 2 seconds, tightend it down, never had a problem.

[t3rmin]

Thanks for your replies. ;-)

I'm ashamed to admit I didn't use a torque wrench because I didn't have a proper sized socket that fit the torque wrench and I was in a hurry. I just checked the torque specs chart in my manuals and that bolt had one of the highest torque specs on the whole bike. So I just put some good muscle into it and figured that would do the trick.

So of course that's a horrible thing to do, but I can't see how that would cause a wobble/buzz. Maybe my mistake was whacking it on with the mallet? I wonder if I could have whacked it on slightly crooked but wedged it tight enough that it didn't even out when I torqued it down? Next time I'll just let the bolt seat the rotor.

Also I wonder if the rotor is balanced with or without the starter clutch attached? I swapped the starter clutch from my old rotor 'cause it was in better shape -- could that have thrown off the balance do you think?

[Jethro]

I've spent hundreds (literally HUNDREDS) of hours chasing the cause of why my bike vibrates so badly. It's so bad that I have to carry a handfull of spare tank mounting bolts becasue they snap every once in a while. I've claimed defeat and simply bought a new bike, almost exclusivley becasue of this.

But enough about me, did the bike vibrate at all before?

[t3rmin]

I've spent hundreds (literally HUNDREDS) of hours chasing the cause of why my bike vibrates so badly. It's so bad that I have to carry a handfull of spare tank mounting bolts becasue they snap every once in a while. I've claimed defeat and simply bought a new bike, almost exclusivley becasue of this.

But enough about me, did the bike vibrate at all before?

I hear you about trying to eliminate vibration! Yes, the bike had a *slight* buzz before, as I gather most GSs do, around 5k. But after valves were adjusted and carbs synced, it was mostly a non-issue. It wasn't enough to numb the hands or snap bolts by any means. It wasn't jarring or offensive or embarrassing. Now it's so loud and grating that I'm afraid my buddies will tease me and what's more the engine will blow a bearing! Every time I gun the motor into the power band I cringe. It's a whole different thing after replacing that rotor. This is past the line of "annoying buzz" and into "freakish vibration of doom" territory! :shock:

[Dink]

The stator rotor is a seperate piece to the starter clutch.
I suggest you remove the rotor, and get a machinist to balance it again for you.
Most sources of vibration in these motors are from clutch baskets (& the wear that an out of balance clutch basket causes) or stator rotors.

Dink

[t3rmin]

The stator rotor is a seperate piece to the starter clutch.
I suggest you remove the rotor, and get a machinist to balance it again for you.
Most sources of vibration in these motors are from clutch baskets (& the wear that an out of balance clutch basket causes) or stator rotors.

Dink

Sounds like good advice! Any idea what a typical charge for that kind of job is? Doesn't seem like it'd be too terrible much...

[Dink]

Sounds like good advice! Any idea what a typical charge for that kind of job is? Doesn't seem like it'd be too terrible much...

I would expect to pay an hour's labour.

Dink

[argonsagas]

Take Dink's advice.


The part may have been misaligned when installing, and that could have caused the vibration, but you have to remove it anyway, so have it balanced and be sure.


When re-installing, press it into place by hand only until snug, check its accuracy, then tighten with a wrench. Blue Loctite will also work here.

[BadBillyB]

I can find another rotor fairly cheaply/easily on eBay, but I'm a little concerned about being able to pull that bolt out after I installed it with red loctite (per the manual)...

If you heat the bolt head with a propane torch (so as not to get it too hot) it will help release the loctite.....I suspect that the rotor and starter clutch (without rollers and springs) are balanced as an assembly. Bolting the starter clutch back on in a different position or replacing it with another unit will cause the balance to be off....If you were to have someone balance it you would want them to find the best position out of 3 that would give the least imbalance before taking weight off......This being said, you may be better off to look for another assembly that still has the starter clutch intact........OR....swap your old starter clutch back on using markings and a magnifying glass to try to put it back on the way it came from the factory......Hope this helps....BadBillyB

[SqDancerLynn1]

I would sugest that you remove the cover & tilt the bike over to one side and run the motor for a few seconds to see if the rotor runs true. If it was not removed properly by the previous owner it could be bent out of round
No amount of balancing will fix it. You could also run it without the rotor
THIS IS WHY IT IS VERY IMPORTANT TO USE THE CORECT REMOVAL TOOL

[t3rmin]

IIf it was not removed properly by the previous owner it could be bent out of round
No amount of balancing will fix it. You could also run it without the rotor
THIS IS WHY IT IS VERY IMPORTANT TO USE THE CORECT REMOVAL TOOL

Yeah, improper removal by PO had crossed my mind. I know I had to bang on my old one a bit with a hammer to break it loose, but that was the broken one so it didn't matter.

Good idea running the bike without the rotor. I will have to give that a try and see how it feels.

Thanks.